Seasonal Histology and Histochemistry of the Adenohypophysis of Nile Tilapia

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6039

Adenohypophysis of Nile Tilapia El-Sakhawy et al.

Fig (19): Transmission electron micrograph of Langerhans cell of adult camel epidermis showing, the cell with light cytoplasm (c), round to oval nucleus (N) and one specific granule (arrow). (Mic. Mag. X 5000)

Seasonal Histology and Histochemistry of the Adenohypophysis of Nile Tilapia (Oreochromis niloticus)

El-Sakhawy, M.A; El-Shammaa, M.A; Abd Rabou, M.I; El-Saba, A.A and Hussein, S.H Department of Cytology and Histology, faculty of Veterinary Medicine Cairo University. _______________________________________________________________ With 20 figures Received June, accepted for publication September, 2011

Abstract

In the present research, the histolo-gy and histochemistry of the adeno-hypophysis of Nile tilapia were done on 96 sexually mature Nile tilapia fish of both sexes collected monthly from the River Nile at Giza over the period from September 2009 to Au-gust 2010. The pituitary gland of both sexually mature male and fe-male Nile tilapia was identically similar during the spring, summer and autumn seasons (breeding seasons). The pituitary gland re-vealed two well distinguished areas, the adenohypophysis and the neu-rohypophysis. The adenohypophy-sis showed three histologically dis-tinct regions: rostral pars distalis, proximal pars distalis, and pars in-termedia with no clear demarcation between them. The adenohypophy-sis was differentiated into two main cellular groups; the chromophobes and chromophils. The chromophils were differentiated into seven types

of cells arranged in mosaic appear-ance; the acidophils (lactotrops and somatotrops); the basophiles (corti-cotrops, thyrotrops and gonado-trops); and the amphiphils (melano-trops and somatolactotrops). In be-tween the adenhypophyseal cells few cavities either empty or partially filled with an amorphous, non-cellular colloid-like material were present. All parts of the adenohypo-physis were penetrated by bran-ching strands of neurohypophyseal tissue, which were coarser and ex-tensive in the pars intermedia. Dur-ing winter (non-breeding season), the adenhypophyseal glandular cells were smaller, less in field oc-cupation and less in the intensity of their staining reactions.

Key words

Nile tilapia, the pituitary gland, the adenohypophysis.

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6040


Introduction

Nile tilapia belongs to genus Oreochromis. This species is natu-rally distributed in the Nile River as well as most parts of African Rivers and lakes. Oreochromis niloticus is gonochoristic, which each individual possessing a single sexual pheno-type. Nile tilapia is characterized by extended spawning seasons, matur-ity at small size and a fast growth rate. (Peterson etal., 2004). Oreoch-romis niloticus is locally known as “Nile Bolti” or “Nile tilapia” and is so far one of the most important cul-tured species as food fish in Egypt either in pond culture or via other methods of fish farming (Mousa and Mousa, 1999a). The organization of the teleostean pituitary gland has been the subject of reviews (Ball and Baker, 1969; Sage and Bern, 1971; Schreibman et al.,1973) and Holmes and Ball, 1974). The study of the histology of the pituitary gland of the different teleost fish attracts the attention of several investigators such as Yoakim (1971) in Synodon-tus schall; Mousa (1998) in Nile ti-lapia (Oreochromis niloticus); Mou-sa and Mousa (1998) in mullet (Mu-gil cephalus); Mousa and Mousa (1999a) in Nile tilapia (Oreochromis niloticus) and Gaber (2000) in Ba-grus docmac and Bagrus bayad. As far as we are aware, there are few references dealing with the season-

al changes in the histology and his-tochemistry of the adenohypophysis of Nile tilapia (Oreochromis niloti-cus) (Mousa and Mousa, 1999a). The principle objectives of the present investigation was to study the seasonal activity of the adeno-hypophysis to provide a clear infor-mation which could be useful for both scientists and who concerning with aquaculture development.

Materials and Methods

Specimens of Nile tilapia (Oreoch-romis niloticus) were collected monthly at the same time of the day from the River Nile at Giza. A total of 96 sexually mature Nile tilapia fish of both sexes were collected over the period from September 2009 to August 2010. Fish were transported alive to the central lab. of Cytology and Histology depart-ment, faculty of Veterinary Medicine Cairo University. The pituitary glands were removed immediately after decapitation and fixed in for-mol-sublimte and neutral buffered formalin for about 24hs., also Bouin′s fluid, Susa, Zenker’s formol and Bouin-hollande sublimt were used for 12hs. After proper time of fixation for each fixative the samples were dehydrated, embedded in pa-raplast and following that 5-6 μm. sections were cut in sagittal plane.

The following staining procedures were adopted for general histologi-cal examination.

1. Harris haematoxylin and eosin (H&E) for general histological ex-amination.

2. Crossmon’s trichrome stain for identification of collagen fibers and smooth muscle fibers (Crossmon, 1937).

3. Weighert’s elastic stain for dem-onstration of elastic fibers.

4. Gomori’s reticuline method for demonstration of reticular fibers.

The aforementioned fixatives and staining, methods were used as out-lined by Drury and Wallington (1980).

The pituitary gland was specially stained for identification of the dif-ferent cell types on the basis of their chemical constituents, by the follow-ing methods:

1. Aldehyde fuchsin - Orange G – Light green (AF-OG-LG) for demon-stration of thyrotrops, gonadotrops, somatotrops (Halmi, 1952).

2. Periodic acid schiff technique - Orange G – Light green (PAS – OG-LG) for demonstration of somato-trops, thyrotrops, corticotrops (Pearse, 1972).

3. Peracetic acid- Alcian blue PH 0.2- Periodic acid schiff -Orange G (PA- AB - PAS – OG) for demon-stration of thyrotrops, somatotrops, gonadotrops and lactotrops (Heath, 1965).

4. Aldehyde thionin- Periodic acid schiff - Orange G (Ath-PAS-OG) for demonstration of thyrotrops, gona-dotrops, corticotrops and melano-trops (Ezrin and Murray, 1963).

5. Azocarmine-Aniline blue- Orange G (Heidenhain’s azan modification) for demonstration of somatotrops and lactotrops (Bancroft and Ste-vens, 1982).

6. Combined stain for fish pituitary (Performic acid - Alcian blue - Peri-odic acid schiff - Orange G-Acid fuchsin) for demonstration of lacto-trops, corticotrops, melanotrops, somatotrops, gonadotrops and thy-rotrops (Jafri, 1979).

7. Lead haematoxyline - Periodic acid schiff (PbH – PAS) for demon-stration of corticotrops, melano-trops, somatolactotrops and gona-dotrops (Bancroft and Stevens, 1982).

Results

In the present research, the histolo-gy and histochemistry of the adeno-hypophysis of Nile tilapia (Oreoch-romis niloticus) were described in

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6041


Introduction

Nile tilapia belongs to genus Oreochromis. This species is natu-rally distributed in the Nile River as well as most parts of African Rivers and lakes. Oreochromis niloticus is gonochoristic, which each individual possessing a single sexual pheno-type. Nile tilapia is characterized by extended spawning seasons, matur-ity at small size and a fast growth rate. (Peterson etal., 2004). Oreoch-romis niloticus is locally known as “Nile Bolti” or “Nile tilapia” and is so far one of the most important cul-tured species as food fish in Egypt either in pond culture or via other methods of fish farming (Mousa and Mousa, 1999a). The organization of the teleostean pituitary gland has been the subject of reviews (Ball and Baker, 1969; Sage and Bern, 1971; Schreibman et al.,1973) and Holmes and Ball, 1974). The study of the histology of the pituitary gland of the different teleost fish attracts the attention of several investigators such as Yoakim (1971) in Synodon-tus schall; Mousa (1998) in Nile ti-lapia (Oreochromis niloticus); Mou-sa and Mousa (1998) in mullet (Mu-gil cephalus); Mousa and Mousa (1999a) in Nile tilapia (Oreochromis niloticus) and Gaber (2000) in Ba-grus docmac and Bagrus bayad. As far as we are aware, there are few references dealing with the season-

al changes in the histology and his-tochemistry of the adenohypophysis of Nile tilapia (Oreochromis niloti-cus) (Mousa and Mousa, 1999a). The principle objectives of the present investigation was to study the seasonal activity of the adeno-hypophysis to provide a clear infor-mation which could be useful for both scientists and who concerning with aquaculture development.

Materials and Methods

Specimens of Nile tilapia (Oreoch-romis niloticus) were collected monthly at the same time of the day from the River Nile at Giza. A total of 96 sexually mature Nile tilapia fish of both sexes were collected over the period from September 2009 to August 2010. Fish were transported alive to the central lab. of Cytology and Histology depart-ment, faculty of Veterinary Medicine Cairo University. The pituitary glands were removed immediately after decapitation and fixed in for-mol-sublimte and neutral buffered formalin for about 24hs., also Bouin′s fluid, Susa, Zenker’s formol and Bouin-hollande sublimt were used for 12hs. After proper time of fixation for each fixative the samples were dehydrated, embedded in pa-raplast and following that 5-6 μm. sections were cut in sagittal plane.

The following staining procedures were adopted for general histologi-cal examination.

1. Harris haematoxylin and eosin (H&E) for general histological ex-amination.

2. Crossmon’s trichrome stain for identification of collagen fibers and smooth muscle fibers (Crossmon, 1937).

3. Weighert’s elastic stain for dem-onstration of elastic fibers.

4. Gomori’s reticuline method for demonstration of reticular fibers.

The aforementioned fixatives and staining, methods were used as out-lined by Drury and Wallington (1980).

The pituitary gland was specially stained for identification of the dif-ferent cell types on the basis of their chemical constituents, by the follow-ing methods:

1. Aldehyde fuchsin - Orange G – Light green (AF-OG-LG) for demon-stration of thyrotrops, gonadotrops, somatotrops (Halmi, 1952).

2. Periodic acid schiff technique - Orange G – Light green (PAS – OG-LG) for demonstration of somato-trops, thyrotrops, corticotrops (Pearse, 1972).

3. Peracetic acid- Alcian blue PH 0.2- Periodic acid schiff -Orange G (PA- AB - PAS – OG) for demon-stration of thyrotrops, somatotrops, gonadotrops and lactotrops (Heath, 1965).

4. Aldehyde thionin- Periodic acid schiff - Orange G (Ath-PAS-OG) for demonstration of thyrotrops, gona-dotrops, corticotrops and melano-trops (Ezrin and Murray, 1963).

5. Azocarmine-Aniline blue- Orange G (Heidenhain’s azan modification) for demonstration of somatotrops and lactotrops (Bancroft and Ste-vens, 1982).

6. Combined stain for fish pituitary (Performic acid - Alcian blue - Peri-odic acid schiff - Orange G-Acid fuchsin) for demonstration of lacto-trops, corticotrops, melanotrops, somatotrops, gonadotrops and thy-rotrops (Jafri, 1979).

7. Lead haematoxyline - Periodic acid schiff (PbH – PAS) for demon-stration of corticotrops, melano-trops, somatolactotrops and gona-dotrops (Bancroft and Stevens, 1982).

Results

In the present research, the histolo-gy and histochemistry of the adeno-hypophysis of Nile tilapia (Oreoch-romis niloticus) were described in

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6042


detail during the spring, summer and autumn seasons of the year (from March to November) to estab-lish a standard against which the subsequent season of the year (win-ter) would be compared. The struc-ture of the pituitary gland of both sexually mature male and female Nile tilapia (Oreochromis niloticus) was identically similar throughout the year. The pituitary gland of Nile tilapia (Oreochromis niloticus) re-vealed two well distinguished areas, the adenohypophysis and the neu-rohypophysis. The adenohypophy-sis was covered by a thin fibrous delicate capsule of fine collagenous, elastic, and few reticular fibers. The capsule was richly supplied with subcapsular blood vessels (Fig. 1). The supporting tissue was formed of reticular net. The adenohypophysis of the Nile tilapia (Oreochromis nilo-ticus) revealed three histologically distinct regions: rostral pars distalis (RPD), proximal pars distalis (PPD), and Pars intermedia (PI) (Fig. 2). There was no clear demarcation between the three regions. The cells forming the adenohypophysis were arranged in cords and clumps or cell clusters (Fig. 3). Few cavities of va-riable sizes were observed, their lumina were either empty or filled with an amorphous, non-cellular col-loid-like materials stained with orange G and azocarmine (Fig. 4). The cells of the epithelial compo-

nent of the adenohypophysis were differentiated into two main groups; the chromophobes lack specific granules and hence showed only a faint cytoplasmic staining reaction. On the other hand, the chromophils were differentiated into acidophils, basophils and amphiphils. The aci-dophils (lactotrops and somato-trops) had a strong preference for acid dyes; the basophils (cortico-trops, thyrotrops and gonadotrops) had a strong preference for basic dyes and the amphiphils (melano-trops and somatolactotrops) stained with both acid and basic dyes. There was a large number of blood sinusoids, which were highly en-gorged with blood distinguished along the whole adenohypophysis. All parts of the adenohypophysis were penetrated by branching strands of neurohypophyseal tissue. There was a more extensive interdi-gitation between the neurohypophy-seal tissue and pars intermedia (PI) (Fig. 5). The neurohypophysis was composed of a mesh work of axonal non-myelinated nerve fibers and neuroglial cells (Fig.10). Large blood sinusoids engorged with blood were present. Moreover, neu-rosecretory colloid droplets were evident.

Lactotrops: lactotrops or ("prolac-tin") cells formed the major compo-nent in the rostral pars distalis. Lac-totrops were separated from the

neurohypophysis by the layer of cor-ticotrops cells. Islets of lactotrops were detected in the proximal pars distalis, and isolated cells appeared subcapsular in the pars intermedia (Fig. 6). Lactotrops were usually large, generally round or oval cells, with granulated cytoplasm, and had a large, eccentric nucleus. Lacto-trops were not grouped into follicles. They were positive to orange G (Figs. 7).

Corticotrops: corticotrops were ar-ranged into cords and islets in the rostral pars distalis, bordering the neurohypophysis, and in the junc-tion between the rostral pars distalis and proximal pars distalis. Further-more, isolated cells were found dis-persed deep in the proximal pars distalis. Corticotrops were angular or polygonal in shape with round eccentric vesicular nuclei with prom-inent nucleoli. The cytoplasm of cor-ticotrops possessed a strong affinity to light green. Moreover, they stained grey with lead haematox-yline. Some of the corticotrops ap-peared degranulated (Fig. 8).

Somatotrops: Somatotrops were arranged into highly convoluted mul-ticellular layers of cords arranged in long chain bordering the neurohy-pophyseal tissue which penetrated the proximal pars distalis, dispersed among gonadotrops, dispersed also in the proximal pars distalis border-

ing pars intermedia and in the pars intermedia between the melano-trops and somatolactotrops border-ing the neurohypophysis. Somato-trops were round, columnar or ovoid cells of variable sizes. Somatotrops had an eccentric, large vesicular nucleus with distinct one or two nuc-leoli. Somatotrops had azocarmino-philic affinity (Fig. 9), acid fuchsin and orange G positive.

Gonadotrops: they form the main bulk of cells of the adenohypophysis during spring, summer and autumn seasons. Gonadotrops were located throughout the adenohypophysis, with the largest population occurred in the proximal pars distalis and along its junction with the pars in-termedia (Fig.10). Isolated cells were also observed intermingled with other cells of rostral pars dista-lis and proximal pars distalis. These cells showed cytoplasmic protru-sions shortly extending between the somatotrops (Fig.11). During these season, gonadotrops were numer-ous and larger in size than other cell types. Their cytoplasm showed dif-ferent stages of granulation, de-granulation and vacuolation. Some cells appeared nearly empty (Fig. 12). Gonadotrops were angular, oval or polygonal in shape. Their nuclei were vesicular, contained many nucleoli. Gonadotrops were basophilic cells gave intense period-ic acid schiff positive reaction. Go-

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6043


detail during the spring, summer and autumn seasons of the year (from March to November) to estab-lish a standard against which the subsequent season of the year (win-ter) would be compared. The struc-ture of the pituitary gland of both sexually mature male and female Nile tilapia (Oreochromis niloticus) was identically similar throughout the year. The pituitary gland of Nile tilapia (Oreochromis niloticus) re-vealed two well distinguished areas, the adenohypophysis and the neu-rohypophysis. The adenohypophy-sis was covered by a thin fibrous delicate capsule of fine collagenous, elastic, and few reticular fibers. The capsule was richly supplied with subcapsular blood vessels (Fig. 1). The supporting tissue was formed of reticular net. The adenohypophysis of the Nile tilapia (Oreochromis nilo-ticus) revealed three histologically distinct regions: rostral pars distalis (RPD), proximal pars distalis (PPD), and Pars intermedia (PI) (Fig. 2). There was no clear demarcation between the three regions. The cells forming the adenohypophysis were arranged in cords and clumps or cell clusters (Fig. 3). Few cavities of va-riable sizes were observed, their lumina were either empty or filled with an amorphous, non-cellular col-loid-like materials stained with orange G and azocarmine (Fig. 4). The cells of the epithelial compo-

nent of the adenohypophysis were differentiated into two main groups; the chromophobes lack specific granules and hence showed only a faint cytoplasmic staining reaction. On the other hand, the chromophils were differentiated into acidophils, basophils and amphiphils. The aci-dophils (lactotrops and somato-trops) had a strong preference for acid dyes; the basophils (cortico-trops, thyrotrops and gonadotrops) had a strong preference for basic dyes and the amphiphils (melano-trops and somatolactotrops) stained with both acid and basic dyes. There was a large number of blood sinusoids, which were highly en-gorged with blood distinguished along the whole adenohypophysis. All parts of the adenohypophysis were penetrated by branching strands of neurohypophyseal tissue. There was a more extensive interdi-gitation between the neurohypophy-seal tissue and pars intermedia (PI) (Fig. 5). The neurohypophysis was composed of a mesh work of axonal non-myelinated nerve fibers and neuroglial cells (Fig.10). Large blood sinusoids engorged with blood were present. Moreover, neu-rosecretory colloid droplets were evident.

Lactotrops: lactotrops or ("prolac-tin") cells formed the major compo-nent in the rostral pars distalis. Lac-totrops were separated from the

neurohypophysis by the layer of cor-ticotrops cells. Islets of lactotrops were detected in the proximal pars distalis, and isolated cells appeared subcapsular in the pars intermedia (Fig. 6). Lactotrops were usually large, generally round or oval cells, with granulated cytoplasm, and had a large, eccentric nucleus. Lacto-trops were not grouped into follicles. They were positive to orange G (Figs. 7).

Corticotrops: corticotrops were ar-ranged into cords and islets in the rostral pars distalis, bordering the neurohypophysis, and in the junc-tion between the rostral pars distalis and proximal pars distalis. Further-more, isolated cells were found dis-persed deep in the proximal pars distalis. Corticotrops were angular or polygonal in shape with round eccentric vesicular nuclei with prom-inent nucleoli. The cytoplasm of cor-ticotrops possessed a strong affinity to light green. Moreover, they stained grey with lead haematox-yline. Some of the corticotrops ap-peared degranulated (Fig. 8).

Somatotrops: Somatotrops were arranged into highly convoluted mul-ticellular layers of cords arranged in long chain bordering the neurohy-pophyseal tissue which penetrated the proximal pars distalis, dispersed among gonadotrops, dispersed also in the proximal pars distalis border-

ing pars intermedia and in the pars intermedia between the melano-trops and somatolactotrops border-ing the neurohypophysis. Somato-trops were round, columnar or ovoid cells of variable sizes. Somatotrops had an eccentric, large vesicular nucleus with distinct one or two nuc-leoli. Somatotrops had azocarmino-philic affinity (Fig. 9), acid fuchsin and orange G positive.

Gonadotrops: they form the main bulk of cells of the adenohypophysis during spring, summer and autumn seasons. Gonadotrops were located throughout the adenohypophysis, with the largest population occurred in the proximal pars distalis and along its junction with the pars in-termedia (Fig.10). Isolated cells were also observed intermingled with other cells of rostral pars dista-lis and proximal pars distalis. These cells showed cytoplasmic protru-sions shortly extending between the somatotrops (Fig.11). During these season, gonadotrops were numer-ous and larger in size than other cell types. Their cytoplasm showed dif-ferent stages of granulation, de-granulation and vacuolation. Some cells appeared nearly empty (Fig. 12). Gonadotrops were angular, oval or polygonal in shape. Their nuclei were vesicular, contained many nucleoli. Gonadotrops were basophilic cells gave intense period-ic acid schiff positive reaction. Go-

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6044


nadotrops were stained dark blue with aldehyde thionin. They showed great affinity to aldehyde fuchsin and aniline blue.

Thyrotrops: Thyrotrops were lo-cated in the proximal pars distalis (Fig. 13). Thyrotrops scattered in small islets in between the somato-trops in the proximal pars distalis near the neurohypophysis. Isolated thyrotrops were present among oth-er cells of the proximal pars distalis, and along the periphery of the pars intermedia among the gonadotrops. Thyrotrops were small, angular, and irregular or polygonally shaped cells, each contained distinct fine cytoplasmic granules and round ve-sicular nucleus, with 1-2 nucleoli placed at one end of the cell. The thyrotrops were relatively fewer and smaller than gonadotrops and pos-sessed cytoplasmic processes. These cells showed the same histo-chemical staining affinities as gona-dotrops but their staining affinity was weaker.

Melanotrops: Melanotrops, the amphiphilic cells, were the predomi-nant cell type mainly restricted to the pars intermedia, forming clus-ters and small groups of cells in the central parts of the pars intermedia (PI), lying further away from the neural tissue (Fig.14). Melanotrops were observed in the dorsal proxim-al pars distalis among the gonado-

trops. Melanotrops were lead hae-matoxyline positive (PbH + cells). Melanotrops stained bluish with ani-line blue. Melanotrops were larger, columnar cells with basal nucleus and a supranuclear mass of staina-ble secretory granules. Melanotrops showed great staining affinity to orange G and light green (Fig. 15)

Somatolactotrops: The somatolac-totrops were amphiphilic cells for-med a discontinuous layer bordering the neurohypophysis, or away from the neurohypophysis dispersed be-tween melanotrops. Somatolacto-trops were small sized cells, with oval or roundish shape. The nucleus was clear, round, oval or deeply in-dented. The somatolactotrops were moderatly reacted to periodic acid–schiff (PAS + cells) (Fig.16). The somatolactotrops produce pale blue color when stained with aldehyde fuchsin. They were positively stain-ed with the acidic dye azocarmine (Fig. 17).

Winter season (from December to February):

Lactotrops: Few cells showed gra-nulated cytoplasm and others ap-peared vacuolated and empty.

Corticotrops: of both sexes had the same features throughout the year.

Somatotrops: of both sexes show-ed clear seasonal variation as they appeared smaller in size. Some were fully filled with fine cytoplasmic granules. Others, appeared partially degranulated, even, some were chromophobic.

Gonadotrops: in both sexes, they were smaller in size and less in field occupation. Most of these cells were densely granulated. Few cells re-vealed partial degranulation and vacuolation (Fig. 18).

Thyrotrops: many thyrotrops of both sexes appeared degranulated and vacuolated (Fig.19).

Somatolactotrops and Melano-trops: Staining intensities and number of both melanotrops and somatolactotrops appeared greatly reduced. Moreover, melanotrops appeared greatly degranulated. The somatolactotrops showed different staining pattern, as they were stained with both lead haematox-yline and periodic acid schiff (Fig. 20).

Discussion

In agreement with the results of Ball and Baker (1969) in teleost fish; Yoakim (1971) in Nile catfish (Syn-odontus schall); Mousa (1998) in Nile tilapia (Oreochromis niloticus) and El-Zoghbyet al., (2008) in Cla-rias lazera, this study revealed that

the pituitary gland of Oreochromis niloticus as in most teleosts was composed of two parts without dis-tinct line of demarcation between them; the adenohypophysis which was the glandular part and neuro-hypophysis which was the neural part of the gland.

In accordance to Ball and Baker (1969); Peter et al., (1990) in teleost fishes; Cinquetti and Dramis (2006) in Padogobius marteusi and Kasper, et al., (2006) in Oreochromis niloti-cus, our finding revealed that The neurohypophysis gave off ramifica-tions to the different parts of the adenohypophysis. The interdigita-tion of the neurohypophysis with the pars intermedia (PI) was coarser and more numerous.

Weltzien, et al., (2004) in flatfish (Pleuronectiformes) and Kasper et al. (2006) in Oreochromis niloticus stated that, unlike mammals, teleost fish lack a hypothalamo-hypo-physeal portal system for the trans-port of neurohormonal regulators. Instead, a direct axonal transport existed between hypothalamic neu-rons and pituitary endocrine cells via the hypophyseal stalk and neu-rohypophysis.

The adenohypophysis of the Nile tilapia was subdivided into three dis-tinct regions; the most rostral region was the rostral pars distalis (RPD),

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6045


nadotrops were stained dark blue with aldehyde thionin. They showed great affinity to aldehyde fuchsin and aniline blue.

Thyrotrops: Thyrotrops were lo-cated in the proximal pars distalis (Fig. 13). Thyrotrops scattered in small islets in between the somato-trops in the proximal pars distalis near the neurohypophysis. Isolated thyrotrops were present among oth-er cells of the proximal pars distalis, and along the periphery of the pars intermedia among the gonadotrops. Thyrotrops were small, angular, and irregular or polygonally shaped cells, each contained distinct fine cytoplasmic granules and round ve-sicular nucleus, with 1-2 nucleoli placed at one end of the cell. The thyrotrops were relatively fewer and smaller than gonadotrops and pos-sessed cytoplasmic processes. These cells showed the same histo-chemical staining affinities as gona-dotrops but their staining affinity was weaker.

Melanotrops: Melanotrops, the amphiphilic cells, were the predomi-nant cell type mainly restricted to the pars intermedia, forming clus-ters and small groups of cells in the central parts of the pars intermedia (PI), lying further away from the neural tissue (Fig.14). Melanotrops were observed in the dorsal proxim-al pars distalis among the gonado-

trops. Melanotrops were lead hae-matoxyline positive (PbH + cells). Melanotrops stained bluish with ani-line blue. Melanotrops were larger, columnar cells with basal nucleus and a supranuclear mass of staina-ble secretory granules. Melanotrops showed great staining affinity to orange G and light green (Fig. 15)

Somatolactotrops: The somatolac-totrops were amphiphilic cells for-med a discontinuous layer bordering the neurohypophysis, or away from the neurohypophysis dispersed be-tween melanotrops. Somatolacto-trops were small sized cells, with oval or roundish shape. The nucleus was clear, round, oval or deeply in-dented. The somatolactotrops were moderatly reacted to periodic acid–schiff (PAS + cells) (Fig.16). The somatolactotrops produce pale blue color when stained with aldehyde fuchsin. They were positively stain-ed with the acidic dye azocarmine (Fig. 17).

Winter season (from December to February):

Lactotrops: Few cells showed gra-nulated cytoplasm and others ap-peared vacuolated and empty.

Corticotrops: of both sexes had the same features throughout the year.

Somatotrops: of both sexes show-ed clear seasonal variation as they appeared smaller in size. Some were fully filled with fine cytoplasmic granules. Others, appeared partially degranulated, even, some were chromophobic.

Gonadotrops: in both sexes, they were smaller in size and less in field occupation. Most of these cells were densely granulated. Few cells re-vealed partial degranulation and vacuolation (Fig. 18).

Thyrotrops: many thyrotrops of both sexes appeared degranulated and vacuolated (Fig.19).

Somatolactotrops and Melano-trops: Staining intensities and number of both melanotrops and somatolactotrops appeared greatly reduced. Moreover, melanotrops appeared greatly degranulated. The somatolactotrops showed different staining pattern, as they were stained with both lead haematox-yline and periodic acid schiff (Fig. 20).

Discussion

In agreement with the results of Ball and Baker (1969) in teleost fish; Yoakim (1971) in Nile catfish (Syn-odontus schall); Mousa (1998) in Nile tilapia (Oreochromis niloticus) and El-Zoghbyet al., (2008) in Cla-rias lazera, this study revealed that

the pituitary gland of Oreochromis niloticus as in most teleosts was composed of two parts without dis-tinct line of demarcation between them; the adenohypophysis which was the glandular part and neuro-hypophysis which was the neural part of the gland.

In accordance to Ball and Baker (1969); Peter et al., (1990) in teleost fishes; Cinquetti and Dramis (2006) in Padogobius marteusi and Kasper, et al., (2006) in Oreochromis niloti-cus, our finding revealed that The neurohypophysis gave off ramifica-tions to the different parts of the adenohypophysis. The interdigita-tion of the neurohypophysis with the pars intermedia (PI) was coarser and more numerous.

Weltzien, et al., (2004) in flatfish (Pleuronectiformes) and Kasper et al. (2006) in Oreochromis niloticus stated that, unlike mammals, teleost fish lack a hypothalamo-hypo-physeal portal system for the trans-port of neurohormonal regulators. Instead, a direct axonal transport existed between hypothalamic neu-rons and pituitary endocrine cells via the hypophyseal stalk and neu-rohypophysis.

The adenohypophysis of the Nile tilapia was subdivided into three dis-tinct regions; the most rostral region was the rostral pars distalis (RPD),

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6046


the middle region was the proximal pars distalis (PPD), while the most distal region was the pars interme-dia (PI). Our classification came in agreement to those obtained by Oli-vereau and Ball (1964) in teleost; Groman (1982) in striped bass; Peuteet al.,(1984) in Clarias lazera; Mousa (1998) in Oreochromis niloti-cus; Gaber (2000) in Bagrus doc-mac and Bagrus bayad; Kasper et al. (2006) in Oreochromis niloticus and El-Zoghby et al. (2008) in Cla-rias lazera.

In agreement with the results of Kasper et al. (2006) in Oreochromis niloticus, the hormone producing cell types were arranged in a mo-saic pattern due to the uneven dis-tribution of different cell types within the three regions of the adenohypo-physis.

El-Zoghby et al. (2008) in Clarias lazera revealed that the adenohy-pophysis was found to be consisted mainly of two main cell types; aci-dophils and basophils. Five cell types were identified in the adeno-hypophysis of the Clarias lazera. El-Gohary (2001) in Oreochromis nilo-ticus identified seven cells; two of them were of unknown function.

Our results came in agreement with Rizkalla (1963) in Oreochromis nilo-ticus and Wai-Sum and Chan (1974) in Monopterus albus where

they revealed that the cells of the epithelial component of the adeno-hypophysis were differentiated into two main groups; the chromo-phobes lack specific granules. On the other hand, the chromophils were differentiated into acidophils, basophils and amphiphils. The aci-dophils (lactotrops and somato-trops), the basophils (corticotrops, gonadotrops and thyrotrops) and the amphiphils (melanotrops and somatolactotrops).

Acidophilic droplets (colloid) stained positively with orange G and azo-carmine often appeared between the adenohypophyseal cellular ele-ments. These were incorporated as an accumulation of hormonal ma-terial (Iturriza, 1964) in Bufo arena-rum or as products of cellular dege-neration (Etkin, 1967).

In our investigation; the lactotrops or ("prolactin") cells (PRL cells) formed the major component in the rostral pars distalis (RPD). Lactotrops were separated from the neurohypophy-sis by the layer of corticotrops cells. Islets of lactotrops were detected in the proximal pars distalis (PPD), and individual cells appeared sub-capsular in the pars intermedia. Similar findings were described by Dharmamba and Nishioka (1968) in Tilapia mossambica; Massoud et al. (1985) in Malapterurus electricus; Gaber (2000) in Bagrus docmac

and Bagrus bayad and El-Zoghby et al. (2008) in Clarias lazera.

The present work revealed that lac-totrops were not grouped into fol-licles. The same observations were recorded by Ball and Baker (1969) in striped bass; Benjamin (1979) in Crenilabrus melops and Cinquetti and Dramis (2006) in Padogobius martensi. On the other hands, Ta-kashima and Hibiya (1995) in rain-bow trout; Gaber (2000) in Bagrus docmac and Bagrus bayad and El-Zoghby et al. (2008) in Clarias laze-ra observed that prolactin cells are arranged in definite follicles with ovoid or spherical lumina.

Sanchez et al. (2003) in the greater weever fish emphasized that, in ma-rine fish, prolactin (PRL-ir) cells had been showed to be involved in stress or reproduction.

In our investigation in Oreochromis niloticus, corticotrops (ACTH cells) were arranged into cords and islets in the rostral pars distalis, bordering the neurohypophysis and the rostral pars distalis and in the junction be-tween the rostral pars distalis (RPD) and proximal pars distalis (PPD). Furthermore, isolated cells were found dispersed deep in the prox-imal pars distalis (PPD), that simu-late to the results obtained by Ball and Baker (1969) in teleost; Gaber (2000) in Bagrus docmac and Ba-

grus bayad; Sanchez et al. (2003) in the greater weever fish (Trachi-nus draco); Weltzien et al. (2003) in Atlantic halibut; El-Zoghby et al. (2008) in Clarias lazera and Borella et al. (2009) in Arapaima gigas.

In teleosts, besides its classical functions of stimulating cortisol re-lease and stress-response control, corticotropin (ACTH) acts in adapta-tion to hyposmotic environments (Mancera and Fuentes, 2006 and Borella et al., 2009).

In the present study somatotrops were arranged into highly convo-luted multicellular layers of cords which aligned as long chain border-ing the neurohypophyseal tissue which penetrating the proximal pars distalis (PPD) and dispersed among gonadotrops. The same results were recorded by Mousa (1998) and El-Gohary (2001) in Oreochromis niloticus; Sanchez et al. (2003) in the greater weever fish (Trachinus draco); Agulleiro, et al., (2006) in Oreochromis niloticus and El-Zoghby et al. (2008) in Clarias laze-ra.

Our results observed that, isolated somatotrops also present in the pars intermedia between the mela-notrops and somatolactotrops bor-dering the neurohypophysis as that recorded by Takashima and Hibiya (1995) in salmonids; Weltzien et al.

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6047


the middle region was the proximal pars distalis (PPD), while the most distal region was the pars interme-dia (PI). Our classification came in agreement to those obtained by Oli-vereau and Ball (1964) in teleost; Groman (1982) in striped bass; Peuteet al.,(1984) in Clarias lazera; Mousa (1998) in Oreochromis niloti-cus; Gaber (2000) in Bagrus doc-mac and Bagrus bayad; Kasper et al. (2006) in Oreochromis niloticus and El-Zoghby et al. (2008) in Cla-rias lazera.

In agreement with the results of Kasper et al. (2006) in Oreochromis niloticus, the hormone producing cell types were arranged in a mo-saic pattern due to the uneven dis-tribution of different cell types within the three regions of the adenohypo-physis.

El-Zoghby et al. (2008) in Clarias lazera revealed that the adenohy-pophysis was found to be consisted mainly of two main cell types; aci-dophils and basophils. Five cell types were identified in the adeno-hypophysis of the Clarias lazera. El-Gohary (2001) in Oreochromis nilo-ticus identified seven cells; two of them were of unknown function.

Our results came in agreement with Rizkalla (1963) in Oreochromis nilo-ticus and Wai-Sum and Chan (1974) in Monopterus albus where

they revealed that the cells of the epithelial component of the adeno-hypophysis were differentiated into two main groups; the chromo-phobes lack specific granules. On the other hand, the chromophils were differentiated into acidophils, basophils and amphiphils. The aci-dophils (lactotrops and somato-trops), the basophils (corticotrops, gonadotrops and thyrotrops) and the amphiphils (melanotrops and somatolactotrops).

Acidophilic droplets (colloid) stained positively with orange G and azo-carmine often appeared between the adenohypophyseal cellular ele-ments. These were incorporated as an accumulation of hormonal ma-terial (Iturriza, 1964) in Bufo arena-rum or as products of cellular dege-neration (Etkin, 1967).

In our investigation; the lactotrops or ("prolactin") cells (PRL cells) formed the major component in the rostral pars distalis (RPD). Lactotrops were separated from the neurohypophy-sis by the layer of corticotrops cells. Islets of lactotrops were detected in the proximal pars distalis (PPD), and individual cells appeared sub-capsular in the pars intermedia. Similar findings were described by Dharmamba and Nishioka (1968) in Tilapia mossambica; Massoud et al. (1985) in Malapterurus electricus; Gaber (2000) in Bagrus docmac

and Bagrus bayad and El-Zoghby et al. (2008) in Clarias lazera.

The present work revealed that lac-totrops were not grouped into fol-licles. The same observations were recorded by Ball and Baker (1969) in striped bass; Benjamin (1979) in Crenilabrus melops and Cinquetti and Dramis (2006) in Padogobius martensi. On the other hands, Ta-kashima and Hibiya (1995) in rain-bow trout; Gaber (2000) in Bagrus docmac and Bagrus bayad and El-Zoghby et al. (2008) in Clarias laze-ra observed that prolactin cells are arranged in definite follicles with ovoid or spherical lumina.

Sanchez et al. (2003) in the greater weever fish emphasized that, in ma-rine fish, prolactin (PRL-ir) cells had been showed to be involved in stress or reproduction.

In our investigation in Oreochromis niloticus, corticotrops (ACTH cells) were arranged into cords and islets in the rostral pars distalis, bordering the neurohypophysis and the rostral pars distalis and in the junction be-tween the rostral pars distalis (RPD) and proximal pars distalis (PPD). Furthermore, isolated cells were found dispersed deep in the prox-imal pars distalis (PPD), that simu-late to the results obtained by Ball and Baker (1969) in teleost; Gaber (2000) in Bagrus docmac and Ba-

grus bayad; Sanchez et al. (2003) in the greater weever fish (Trachi-nus draco); Weltzien et al. (2003) in Atlantic halibut; El-Zoghby et al. (2008) in Clarias lazera and Borella et al. (2009) in Arapaima gigas.

In teleosts, besides its classical functions of stimulating cortisol re-lease and stress-response control, corticotropin (ACTH) acts in adapta-tion to hyposmotic environments (Mancera and Fuentes, 2006 and Borella et al., 2009).

In the present study somatotrops were arranged into highly convo-luted multicellular layers of cords which aligned as long chain border-ing the neurohypophyseal tissue which penetrating the proximal pars distalis (PPD) and dispersed among gonadotrops. The same results were recorded by Mousa (1998) and El-Gohary (2001) in Oreochromis niloticus; Sanchez et al. (2003) in the greater weever fish (Trachinus draco); Agulleiro, et al., (2006) in Oreochromis niloticus and El-Zoghby et al. (2008) in Clarias laze-ra.

Our results observed that, isolated somatotrops also present in the pars intermedia between the mela-notrops and somatolactotrops bor-dering the neurohypophysis as that recorded by Takashima and Hibiya (1995) in salmonids; Weltzien et al.

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6048


(2003) in Atlantic halibut and Kasper et al. (2006) in Oreochromis niloti-cus.

In the present study, the somato-trops exhibited seasonal changes in their activity as they were relatively smaller in size and fewer in number during winter. Melamed et al. (1999) in Tilapia species concluded that gonadotrops and somatotrops ac-tions were of paracrine nature as both of them had the same season-al changes in relation to the gonads.

Our investigations showed that, the gonadotrops formed the main bulk of cells of the adenohypophysis dur-ing spring, summer and autumn seasons. The largest population oc-curred in the proximal pars distalis. Small clusters were located along the periphery of pars intermedia. Isolated cells were also observed intermingled with other cells of the rostral pars distalis and the proximal pars distalis. Similar findings were described by Yoakim (1971) in Syn-odontus schall; Gaber (2000) in Ba-grus domac and Bagrus bayad and El-Gohary (2001) in Oreochromis niloticus.

In our research, gonadotropic cells of Oreochromis niloticus were nu-merous and larger in size than other cell types in spring, summer and autumn. Their cytoplasm showed different stages of coarse cytoplas-

mic granulation, degranulation and vacuolation. Some cells appeared nearly empty.

It remains uncertain whether the teleost pituitary contained one or two types of gonadotropic cells. Some workers had described two distinct cell types; others had found only one type of gonadotrops.

Contrary to the present findings, light microscopical studies of the pituitary of perch (Perca fluviatilis macedonica kar) revealed two types of gonadotrops (Dimovska, 1970 and 1977). Moreover, Yoshiuraet al. (1999) in Japanese eel (Anguilla japonica); Parhar et al. (2002) in the cichlid fish and Kasper et al. (2006) in Oreochromis niloticus described two types of gonadotrops in the proximal pars distalis.

On the other hand and in accor-dance with our findings in Oreoch-romis niloticus a single type of go-nadotrops, located in the proximal pars distalis, had been observed by Gaber (2000) in Bagrus domac and Bagrus bayad; El-Gohary (2001) in Oreochromis niloticus and El-Zoghby et al. (2008) in catfish (Cla-rias lazera).

During winter the gonadotrops in both sexes were smaller in size and less in field occupation. Most of these cells were densely granu-lated. Few cells revealed partial de-

granulation and vacuolation. Similar observations were described by Mousa and Mousa (1998) in Mugil cephalus and El-Zoghby et al. (2008) in catfish (Clarias lazera).

Thyrotrops showed the same histo-chemical staining affinities (as go-nadotrops), but they were weaker or lighter which support the result of Takashima and Hibiya (1995) in some species, such as chum sal-mon, rainbow trout, carp, tuna and red sea bream.

In the present study, the thyrotrops exhibited seasonal changes in their activity in non-breeding season as many cells appeared degranulated and vacuolated that denied the re-sults obtained by Gaber (2000) in Bagrus domac and Bagrus bayad and El-Zoghby et al. (2008) in Cla-rias lazera.

In our investigation pars intermedia contained mainly two amphiphilic cell types, one was lead heamatox-yline positive which was the predo-minant cell type (melanotrops) and the other periodic acid schiff (PAS) positive which were scattered throughout the pars intermedia. These results simulate the findings of Wai-Sum and Chan (1974) in Monopterus albus; Benjamin (1979) in Crenilabrus melops and Cinquetti and Dramis (2006) in Padogobius martensi.

Our studies revealed that, during non-breeding season (winter) the staining intensities and number of melanotrops appeared greatly re-duced. Moreover, melanotrops ap-peared greatly degranulated. Mela-notrops seemed to have no sea-sonal role in the channel catfish, Ictalurus punctatus (Massoud, 1982).

The work of Ball et al.(1972) in te-leost fish indicated that these cells were the source of melanocyte sti-mulating hormone (MSH).

This distribution pattern of the so-matolactotrops cells observed in our study was in agreement with those recorded in Sparus aurata (Villapla-na et al., 1997); in Oreochromis ni-loticus (Mousa and Mousa, 1999b); in male Atlantic halibut (Hippoglos-sus hippoglossus) (Weltzien et al., 2003); in Oreochromis niloticus, (Kasper et al., 2006) and in Arapai-ma gigas, (Borella et al., 2009).

The function of the periodic acid schiff positive somatolactotrops in the pars intermedia was uncertain; they might be involved in the regula-tion of calcium metabolism (Olive-reau et al.,1981), or in the regulation of background color adaptation (Ball and Batten, 1981), or reproduction (Schreibman et al., 1982).

Kaneko (1996) in rainbow trout sug-gested that somatolactotrops was

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6049


(2003) in Atlantic halibut and Kasper et al. (2006) in Oreochromis niloti-cus.

In the present study, the somato-trops exhibited seasonal changes in their activity as they were relatively smaller in size and fewer in number during winter. Melamed et al. (1999) in Tilapia species concluded that gonadotrops and somatotrops ac-tions were of paracrine nature as both of them had the same season-al changes in relation to the gonads.

Our investigations showed that, the gonadotrops formed the main bulk of cells of the adenohypophysis dur-ing spring, summer and autumn seasons. The largest population oc-curred in the proximal pars distalis. Small clusters were located along the periphery of pars intermedia. Isolated cells were also observed intermingled with other cells of the rostral pars distalis and the proximal pars distalis. Similar findings were described by Yoakim (1971) in Syn-odontus schall; Gaber (2000) in Ba-grus domac and Bagrus bayad and El-Gohary (2001) in Oreochromis niloticus.

In our research, gonadotropic cells of Oreochromis niloticus were nu-merous and larger in size than other cell types in spring, summer and autumn. Their cytoplasm showed different stages of coarse cytoplas-

mic granulation, degranulation and vacuolation. Some cells appeared nearly empty.

It remains uncertain whether the teleost pituitary contained one or two types of gonadotropic cells. Some workers had described two distinct cell types; others had found only one type of gonadotrops.

Contrary to the present findings, light microscopical studies of the pituitary of perch (Perca fluviatilis macedonica kar) revealed two types of gonadotrops (Dimovska, 1970 and 1977). Moreover, Yoshiuraet al. (1999) in Japanese eel (Anguilla japonica); Parhar et al. (2002) in the cichlid fish and Kasper et al. (2006) in Oreochromis niloticus described two types of gonadotrops in the proximal pars distalis.

On the other hand and in accor-dance with our findings in Oreoch-romis niloticus a single type of go-nadotrops, located in the proximal pars distalis, had been observed by Gaber (2000) in Bagrus domac and Bagrus bayad; El-Gohary (2001) in Oreochromis niloticus and El-Zoghby et al. (2008) in catfish (Cla-rias lazera).

During winter the gonadotrops in both sexes were smaller in size and less in field occupation. Most of these cells were densely granu-lated. Few cells revealed partial de-

granulation and vacuolation. Similar observations were described by Mousa and Mousa (1998) in Mugil cephalus and El-Zoghby et al. (2008) in catfish (Clarias lazera).

Thyrotrops showed the same histo-chemical staining affinities (as go-nadotrops), but they were weaker or lighter which support the result of Takashima and Hibiya (1995) in some species, such as chum sal-mon, rainbow trout, carp, tuna and red sea bream.

In the present study, the thyrotrops exhibited seasonal changes in their activity in non-breeding season as many cells appeared degranulated and vacuolated that denied the re-sults obtained by Gaber (2000) in Bagrus domac and Bagrus bayad and El-Zoghby et al. (2008) in Cla-rias lazera.

In our investigation pars intermedia contained mainly two amphiphilic cell types, one was lead heamatox-yline positive which was the predo-minant cell type (melanotrops) and the other periodic acid schiff (PAS) positive which were scattered throughout the pars intermedia. These results simulate the findings of Wai-Sum and Chan (1974) in Monopterus albus; Benjamin (1979) in Crenilabrus melops and Cinquetti and Dramis (2006) in Padogobius martensi.

Our studies revealed that, during non-breeding season (winter) the staining intensities and number of melanotrops appeared greatly re-duced. Moreover, melanotrops ap-peared greatly degranulated. Mela-notrops seemed to have no sea-sonal role in the channel catfish, Ictalurus punctatus (Massoud, 1982).

The work of Ball et al.(1972) in te-leost fish indicated that these cells were the source of melanocyte sti-mulating hormone (MSH).

This distribution pattern of the so-matolactotrops cells observed in our study was in agreement with those recorded in Sparus aurata (Villapla-na et al., 1997); in Oreochromis ni-loticus (Mousa and Mousa, 1999b); in male Atlantic halibut (Hippoglos-sus hippoglossus) (Weltzien et al., 2003); in Oreochromis niloticus, (Kasper et al., 2006) and in Arapai-ma gigas, (Borella et al., 2009).

The function of the periodic acid schiff positive somatolactotrops in the pars intermedia was uncertain; they might be involved in the regula-tion of calcium metabolism (Olive-reau et al.,1981), or in the regulation of background color adaptation (Ball and Batten, 1981), or reproduction (Schreibman et al., 1982).

Kaneko (1996) in rainbow trout sug-gested that somatolactotrops was

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6050


involved in reproduction, calcium metabolism, stress, acid-base regu-lation, fat metabolism, back ground adaptation and osmoregulation.

Canepa et al.,(2006) concluded that SL was a pituitary hormone present exclusively in fish and was involved in different physiological effect. They added that there was clear evidence towards a possible in-volvement of somatolactin (SL) in the adaptation to background colors in teleost together with MSH and MCH.

In the present investigation, the two cell types of the pars intermedia showed seasonal changes in their morphology and staining pattern in correlations to seasonal activity which might indicate that they con-cerned in functions other than con-trol of pigmentation. In our opinions a definitive functions of somatolac-totrops has not been determined till now and need more research.

References

Agulleiro, B.; García-Hernández, M. P. and García Ayala, A. (2006): Teleost adenohypo-physis: morphofunctional and developmental aspects. In: Reinecke M, Zaccone G, Kapoor BG (eds) Fish endo-crinology, vol 1. Science

Publishers, Enfield, pp 289 – 323.

Ball, J.N. and Baker, B.I. (1969): The pituitary gland: Anatomy and Histophysiology. In Fish Physiology (Eds. W.S. Hoar, D.J. Randall and E.M. Do-naldson). Vol. II. Academic Press. New York.

Ball, J.N.; Baker, B.I.; Olivereau, M. and Peter, R. E. (1972): In-vestigation on hypothalamic control of adenohypophyseal functions in teleost fishes. Gen. Comp. Endocrinol. 3: 11 – 21.

Ball, J. N. and Batten, T. F. C. (1981): Pituitary and mela-nophore responses to back-ground in Poecillia latipinna (teleostei): Role of the pars intermedia PAS cells. Gen. Comp. Endocrinol. 44: 233 – 248.

Bancroft, V.M. and Stevens, A. (1982): Theory and practice of histological techniques, 2nd Ed. Churlchill Living-stone, Edinburgh, London, New York.

Benjamin, M. (1979): The cell types in the adenohypophysis of the marine teleost (Crenila-brus melops). Acta Zool. 60: 105 – 113.

Borella, M.I.; Venturieri, R. and Mancera, J.M. (2009): Im-munocytochemical identifi-

cation of adenohypophyseal cells in the pirarucu (Ara-paima gigas), an Amazonian basal teleost. Fish Physiol. Biochem. 35: 3 – 16.

Canepa, M.M.; Pandolfi, M.; Mag- gese, M.C. and Vissio, P.G. (2006): Involvement of So-matolactin in background adaptation of the cichlid fish Cichlasoma dimerus. J. of Exp. Zool. 305: 410-419.

Cinquetti, R. and Dramis, L. (2006): Identification and localization of hormone-producing cells in the pituitary of male Pa-dogobius martensi (Pisces, Gobiidae): a histochemical and immunocytochemical study. J. Fish Bio. (68) SB: 235 – 250.

Crossmon, G. (1937): A modification of mallory’s connective tissue stain with discussion of principle involved. Ibid., 69: 33-38.

Dharmamba, M. and Nishioka, R.S. (1968): Response of "prolac-tin-secreting" cells of Tilapia mossambica to environmen-tal salinity. Gen. Comp. En-docrinol. 10: 409 - 420.

Dimovska, A. (1970): Les cellules gonadotropes de I'hypo-physe chez la perche feme-lle sex-uellemnt miire du lac de Doirae (Perca fluviatilis mucedonica Kar.). God. Zb.

Prir. Mat. Fak. Univ. Kiril Me-todij-Skopje, Biol. 23: 55 - 73.

Dimovska, A. (1977): Donnees cyto- logiques sur l'adnohypo-physe de perche de Do'iran (Perca fluuiatilis mucedonica Kar.) dans certaines peri-odes du cycle sexuel. Invest. Pesq. 41: 15 – 32.

Drury, R. A. B. and Wallington, E. A. (1980): Carleton’s histologi-cal technique. Fourth Edition Oxford University Press, New York, Toronto.

El-Gohary, N.M.A.(2001): The effect of water quality on the re-productive biology of the Nile tilapia, Oreochromis niloticus in Lake Manzalah. Ph.D. Thesis. Faculty of Science. Ain Shams University.

El-Zoghby, I. M. A.; Bakry, H. H.; Ghallab, A. M. and Emam, M. A. (2008): Histological studies on the pituitary gland of catfish (Clarias lazera) during different seasons. The 32nd Sci. Conf. of the Egyp.Soc.Of Hist. and Cyto. pp 24 – 35.

Etkin,W.(1967)Relation of the pars intermedia to the hypotha-lamus.In UN euro endocri-nology (L. Martni and WF. Gnong,eds.),Vol.2,pp.22.Academic Press. New York.

Ezrin, C. and Murray, S. (1963): The

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6051


involved in reproduction, calcium metabolism, stress, acid-base regu-lation, fat metabolism, back ground adaptation and osmoregulation.

Canepa et al.,(2006) concluded that SL was a pituitary hormone present exclusively in fish and was involved in different physiological effect. They added that there was clear evidence towards a possible in-volvement of somatolactin (SL) in the adaptation to background colors in teleost together with MSH and MCH.

In the present investigation, the two cell types of the pars intermedia showed seasonal changes in their morphology and staining pattern in correlations to seasonal activity which might indicate that they con-cerned in functions other than con-trol of pigmentation. In our opinions a definitive functions of somatolac-totrops has not been determined till now and need more research.

References

Agulleiro, B.; García-Hernández, M. P. and García Ayala, A. (2006): Teleost adenohypo-physis: morphofunctional and developmental aspects. In: Reinecke M, Zaccone G, Kapoor BG (eds) Fish endo-crinology, vol 1. Science

Publishers, Enfield, pp 289 – 323.

Ball, J.N. and Baker, B.I. (1969): The pituitary gland: Anatomy and Histophysiology. In Fish Physiology (Eds. W.S. Hoar, D.J. Randall and E.M. Do-naldson). Vol. II. Academic Press. New York.

Ball, J.N.; Baker, B.I.; Olivereau, M. and Peter, R. E. (1972): In-vestigation on hypothalamic control of adenohypophyseal functions in teleost fishes. Gen. Comp. Endocrinol. 3: 11 – 21.

Ball, J. N. and Batten, T. F. C. (1981): Pituitary and mela-nophore responses to back-ground in Poecillia latipinna (teleostei): Role of the pars intermedia PAS cells. Gen. Comp. Endocrinol. 44: 233 – 248.

Bancroft, V.M. and Stevens, A. (1982): Theory and practice of histological techniques, 2nd Ed. Churlchill Living-stone, Edinburgh, London, New York.

Benjamin, M. (1979): The cell types in the adenohypophysis of the marine teleost (Crenila-brus melops). Acta Zool. 60: 105 – 113.

Borella, M.I.; Venturieri, R. and Mancera, J.M. (2009): Im-munocytochemical identifi-

cation of adenohypophyseal cells in the pirarucu (Ara-paima gigas), an Amazonian basal teleost. Fish Physiol. Biochem. 35: 3 – 16.

Canepa, M.M.; Pandolfi, M.; Mag- gese, M.C. and Vissio, P.G. (2006): Involvement of So-matolactin in background adaptation of the cichlid fish Cichlasoma dimerus. J. of Exp. Zool. 305: 410-419.

Cinquetti, R. and Dramis, L. (2006): Identification and localization of hormone-producing cells in the pituitary of male Pa-dogobius martensi (Pisces, Gobiidae): a histochemical and immunocytochemical study. J. Fish Bio. (68) SB: 235 – 250.

Crossmon, G. (1937): A modification of mallory’s connective tissue stain with discussion of principle involved. Ibid., 69: 33-38.

Dharmamba, M. and Nishioka, R.S. (1968): Response of "prolac-tin-secreting" cells of Tilapia mossambica to environmen-tal salinity. Gen. Comp. En-docrinol. 10: 409 - 420.

Dimovska, A. (1970): Les cellules gonadotropes de I'hypo-physe chez la perche feme-lle sex-uellemnt miire du lac de Doirae (Perca fluviatilis mucedonica Kar.). God. Zb.

Prir. Mat. Fak. Univ. Kiril Me-todij-Skopje, Biol. 23: 55 - 73.

Dimovska, A. (1977): Donnees cyto- logiques sur l'adnohypo-physe de perche de Do'iran (Perca fluuiatilis mucedonica Kar.) dans certaines peri-odes du cycle sexuel. Invest. Pesq. 41: 15 – 32.

Drury, R. A. B. and Wallington, E. A. (1980): Carleton’s histologi-cal technique. Fourth Edition Oxford University Press, New York, Toronto.

El-Gohary, N.M.A.(2001): The effect of water quality on the re-productive biology of the Nile tilapia, Oreochromis niloticus in Lake Manzalah. Ph.D. Thesis. Faculty of Science. Ain Shams University.

El-Zoghby, I. M. A.; Bakry, H. H.; Ghallab, A. M. and Emam, M. A. (2008): Histological studies on the pituitary gland of catfish (Clarias lazera) during different seasons. The 32nd Sci. Conf. of the Egyp.Soc.Of Hist. and Cyto. pp 24 – 35.

Etkin,W.(1967)Relation of the pars intermedia to the hypotha-lamus.In UN euro endocri-nology (L. Martni and WF. Gnong,eds.),Vol.2,pp.22.Academic Press. New York.

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cells of the human adenohy-pophysis in pregnancy, in cytologic de L’Adenohypo-physe. J. Benoit and C. Da Lage, ed. Edition du CNRS, PARIS, PP. 183 – 199.

Gaber, S.A.O. (2000): Biological, histological and histochemi-cal studies on the reproduc-tive organs and pituitary gland of Bagrus docmac and Bagrus bayad in the Nile wa-ter, with special reference to the Ultrastructure of support-ing tissues. Ph.D.Thesis. Faculty of Science, Zagazig Univeristy.

Groman, D.B. (1982): Histology of striped bass. American Fish-eries Society (Bethesda, Md.), Vol 3.

Halmi, N.S. (1952): Differentiation of two types of basophils cells of the adenohypophysis of the rat and mouse. Stain Tech., 27: 61.

Heath, E.W. (1965): Application of the Peracetic acid alcian blue periodic acid Schiff orange G stain to the sec-tions of the pituitary gland from domestic animals. Am. J. Vet. Res. 26: 368.

Holmes, R. L. and Ball, J.N. (1974): The pituitary gland in teleost fish. In: Holmes RL, Ball JN (eds) The pituitary gland: a comparative account. Cam-

bridge University Press, London, pp 170 –220.

Iturriza, F. C. (1964): Electron- microscopic studies of the pars intermedia of the pi-tuitary of the toad Bufo arenarum. Gen. Comp. En-docrinol. 4, 492 - 502.

Jafri, S.I. (1979): Combined stain for fish pituitary. Stain Technol. 4(2): 3 – 5.

Kaneko, T. (1996): Cell biology of somatolactin. Int. Rev. Cytol. 169: 1–24.

Kasper, R. S; Shved, N.; Takahashi, A.; Reinecke, M. and Eppler, E. (2006): A systematic im-munohistochemical survey of the distribution patterns of GH, prolactin, somatolactin, β–TSH, β–FSH, β–LH, ACTH, and α–MSH in the adenohypophysis of Oreoch-romis niloticus, the Nile tila-pia. Cell Tissue Res. 325: 303 – 313.

Mancera,J.M. and Fuentes,J.(2006): Osmoregulatory action of hypophyseal hormones in te-leosts. In: Reinecke M, Zac-cone G, Kapoor BG (eds) Fish endocrinology, vol 1. Science Publishers, En-field, pp 393 –417.

Massoud,A. (1982): Seasonal histochemical changes in the pi-tuitary gland of channel cat-fish (Ictalurus punctatus) Ph.

D. thesis. Memphis state university, Memphis. TN. 38152.

Massoud, A.; Shenouda, T. and El- Desouky, N. (1985): The cell types of the adenohypophy-sis of the electric catfish Ma-lapterurus electricus lace-pede from Lake Nasser. Del-ta J. Sci (9) (2): 611 – 637.

Melamed, P.; Gur, G.; Rosenfeld, H.; Elizur, A. and Yaron, Z. (1999): Possible interactions between Gonadotrophs and Somatotrophs in the Pituitary of Tilapia: Apparent Roles for Insulin-Like Growth Fac-tor I and Estradiol. Endocri-nology, 140: 1183 – 1191.

Mousa, A. M. (1998): Immunocyto chemical and Histological studies on the reproductive endocrine glands of the Nile tilapia, Oreochromis niloticus (Teleostei, cichlidae). J. Egypt. Ger. soc. zool., 27: 109 - 134.

Mousa, Sh. A. and Mousa, M. A. (1998): Immunocytochemical studies on the Gonadotropic cells in the Pituitary gland of male mullet, Mugil cephalus during the annual reproduc-tive cycle in both natural ha-bitat and capitivity. J. Egypt. Ger. Soc. Zool., 25: 59 - 74.

Mousa, M. A. and Mousa, Sh. A.

(1999a): Immunocytochemi-cal and histological studies on the hypophyseal–gonadal system in the freshwater Nile tilapia, Oreochromis niloticus (L.), during sexual matura-tion and spawning in differ-ent habitats. J Exp Zool 284:343 – 354.

Mousa, M. A. and Mousa, Sh. A. (1999b): Immunocytochemi-cal study on the localization and distribution of the soma-tolactin cells in the pituitary gland and the brain of Oreo-chromis niloticus (Teleostei, Cichlidae). Gen. Comp. En-docrinol 113: 197 – 211.

Olivereau, M. and Ball, J. (1964): Contribution histophysiologie de l´ hypophyse des télèos-teens, en particulier de celle de Poecilia species. Gen. Comp. Endocrinol., 4: 523 - 532.

Olivereau, M.; Lelup, J.; De Luze, A. and Olivereau, J. (1981): Effet de loestradiol sur l axe hypophyso–thyroidien de languille. Gen. Comp. Endo-crinol. 43: 352–363.

Parhar, I.S.; Soga, T.; Sakuma, Y. and Millar, R.P. (2002): Spatio-temporal expression of gonadotropin-releasing hormone receptor subtypes in gonadotropes, somato-tropes and lactotropes in the

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6053


cells of the human adenohy-pophysis in pregnancy, in cytologic de L’Adenohypo-physe. J. Benoit and C. Da Lage, ed. Edition du CNRS, PARIS, PP. 183 – 199.

Gaber, S.A.O. (2000): Biological, histological and histochemi-cal studies on the reproduc-tive organs and pituitary gland of Bagrus docmac and Bagrus bayad in the Nile wa-ter, with special reference to the Ultrastructure of support-ing tissues. Ph.D.Thesis. Faculty of Science, Zagazig Univeristy.

Groman, D.B. (1982): Histology of striped bass. American Fish-eries Society (Bethesda, Md.), Vol 3.

Halmi, N.S. (1952): Differentiation of two types of basophils cells of the adenohypophysis of the rat and mouse. Stain Tech., 27: 61.

Heath, E.W. (1965): Application of the Peracetic acid alcian blue periodic acid Schiff orange G stain to the sec-tions of the pituitary gland from domestic animals. Am. J. Vet. Res. 26: 368.

Holmes, R. L. and Ball, J.N. (1974): The pituitary gland in teleost fish. In: Holmes RL, Ball JN (eds) The pituitary gland: a comparative account. Cam-

bridge University Press, London, pp 170 –220.

Iturriza, F. C. (1964): Electron- microscopic studies of the pars intermedia of the pi-tuitary of the toad Bufo arenarum. Gen. Comp. En-docrinol. 4, 492 - 502.

Jafri, S.I. (1979): Combined stain for fish pituitary. Stain Technol. 4(2): 3 – 5.

Kaneko, T. (1996): Cell biology of somatolactin. Int. Rev. Cytol. 169: 1–24.

Kasper, R. S; Shved, N.; Takahashi, A.; Reinecke, M. and Eppler, E. (2006): A systematic im-munohistochemical survey of the distribution patterns of GH, prolactin, somatolactin, β–TSH, β–FSH, β–LH, ACTH, and α–MSH in the adenohypophysis of Oreoch-romis niloticus, the Nile tila-pia. Cell Tissue Res. 325: 303 – 313.

Mancera,J.M. and Fuentes,J.(2006): Osmoregulatory action of hypophyseal hormones in te-leosts. In: Reinecke M, Zac-cone G, Kapoor BG (eds) Fish endocrinology, vol 1. Science Publishers, En-field, pp 393 –417.

Massoud,A. (1982): Seasonal histochemical changes in the pi-tuitary gland of channel cat-fish (Ictalurus punctatus) Ph.

D. thesis. Memphis state university, Memphis. TN. 38152.

Massoud, A.; Shenouda, T. and El- Desouky, N. (1985): The cell types of the adenohypophy-sis of the electric catfish Ma-lapterurus electricus lace-pede from Lake Nasser. Del-ta J. Sci (9) (2): 611 – 637.

Melamed, P.; Gur, G.; Rosenfeld, H.; Elizur, A. and Yaron, Z. (1999): Possible interactions between Gonadotrophs and Somatotrophs in the Pituitary of Tilapia: Apparent Roles for Insulin-Like Growth Fac-tor I and Estradiol. Endocri-nology, 140: 1183 – 1191.

Mousa, A. M. (1998): Immunocyto chemical and Histological studies on the reproductive endocrine glands of the Nile tilapia, Oreochromis niloticus (Teleostei, cichlidae). J. Egypt. Ger. soc. zool., 27: 109 - 134.

Mousa, Sh. A. and Mousa, M. A. (1998): Immunocytochemical studies on the Gonadotropic cells in the Pituitary gland of male mullet, Mugil cephalus during the annual reproduc-tive cycle in both natural ha-bitat and capitivity. J. Egypt. Ger. Soc. Zool., 25: 59 - 74.

Mousa, M. A. and Mousa, Sh. A.

(1999a): Immunocytochemi-cal and histological studies on the hypophyseal–gonadal system in the freshwater Nile tilapia, Oreochromis niloticus (L.), during sexual matura-tion and spawning in differ-ent habitats. J Exp Zool 284:343 – 354.

Mousa, M. A. and Mousa, Sh. A. (1999b): Immunocytochemi-cal study on the localization and distribution of the soma-tolactin cells in the pituitary gland and the brain of Oreo-chromis niloticus (Teleostei, Cichlidae). Gen. Comp. En-docrinol 113: 197 – 211.

Olivereau, M. and Ball, J. (1964): Contribution histophysiologie de l´ hypophyse des télèos-teens, en particulier de celle de Poecilia species. Gen. Comp. Endocrinol., 4: 523 - 532.

Olivereau, M.; Lelup, J.; De Luze, A. and Olivereau, J. (1981): Effet de loestradiol sur l axe hypophyso–thyroidien de languille. Gen. Comp. Endo-crinol. 43: 352–363.

Parhar, I.S.; Soga, T.; Sakuma, Y. and Millar, R.P. (2002): Spatio-temporal expression of gonadotropin-releasing hormone receptor subtypes in gonadotropes, somato-tropes and lactotropes in the

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6054


cichlid fish. J. Neuroendo-crinol. 14(8): 657-65.

Pearse, A.G.E (1972): Histochem istry. Theoretical and ap-plied. 2nd Ed. Churlchill, London.

Peter, R. E.; Yu, K.; Marchant, T. A. and Rosenblum,P.M. (1990): Direct neural regulation of the teleost adenohypophy-sis. J. Exp. Zool. (256) 4: 84 – 89.

Peterson, M.S.; Brown-Peterson, N.J. and McDonald, J.L. (2004): Reproduction in non-native environments: estab-lishment of the Nile Tilapia Oreochromis niloticus in coastal Mississippi water-sheds. Copeia 2004:842-849.

Peute, J.; De Leeuw, R.; Goos, H.J. and Van Oordt, P.G. (1984): Ultrastucture and immunola-baling of gonadotrops and thyrotrops in the pituitary of the African catfish, Clarias lazera. Cell.Tiss. Res., 238: 95 - 103.

Rizkalla, W. (1963): A comparative study of the pituitary gland of Tilapia nilotica L. and Mugil capito L., Ain Shams Bull. 9: 177 – 211.

Sage, M. and Bern, H.A. (1971): Cytophysiology of the teleost pituitary. International Re-

view of Cytology 31: 339 - 376.

Sanchez cala, F.; Portillo, A.; Mart´in del Rio, M.P. and Mancera, J.M. (2003): Im-munocytochemical characte-rization of adenohypophy-seal cells in the greater weever fish (Trachinus dra-co). Tissue & Cell 35: 169 – 178.

Schreibman, M.; Leatherland, J. F. and McKeown, B. A. (1973): Functional morphology of te-leost pituitary gland. Am. Zool. 13:719 – 742.

Schreibman, M.; Pertschuck, L. P.; Rainford, E. A.; Margolis-Kazan, H. and Gelber, S. J. (1982): The histochemical localization of steroid binding sites in the pituitary gland of a teleost (the platyfish). Cell. Tissue Res. 226: 523 - 530.

Takashima, F. and Hibiya, T. (1995): An atlas of fish mor-phology. Normal and patho-logical features. Kodansha, Tokyo, pp. 128 – 153.

Villaplana, M.; García-Ayala, A.; García-Hernández, M. P. and Agulleiro, B. (1997): On-togeny of immunoreactive somatolactin cells in the pi-tuitary of gilthead sea bream (Sparus aurata L., Teleos-tei). Anat. Embryol. 196: 227 – 234.

Wai-Sum, O. and Chan, S.T.H. (1974): A cytological study on the structure of the pitui-tary gland of Monopterus al-bus (Zuiew). Gen. Comp. Endocrin., 24: 208 - 222.

Weltzien, F.; Andersson, E; Ander sen, O; Tabrizi, K.S and Norberg, B. (2004): The brain – pituitary – gonad axis in male teleost, with special emphasis on flatfish (Pleu-ronectiformes). Comparative Biochemistry and Physiology Part A 137: 447– 477.

Weltzien, F.: Norberg, B.: Helvik, J.V.: Andersen. O: Sawnson, P. and Andersson, E(2003): Identification and localization of eight distinct hormone-producing cell types in the pituitary of male Atlantic ha-libut (Hippoglossus hippog-lossus L.). Comparative Bio-chemistry and Physiology Part A 134: 315-327.

Yoakim, E.G. (1971): Seasonal var iations in the pituitary gland and gonads of the Nile cat-fish (Synodontus schall) in relation to its reproductive cycle. Ph.D. Thesis. Faculty of Science.Ain Shams Uni-versity.

Yoshiura, Y.; Suetake, H. and Aida, K. (1999): Duality of gonado-tropin in a primitive teleost,

Japanese eel (Anguilla japo-nica). Gen. Comp. Endocri-nol. 114: 121–131.

________________ Correspondence: e-mail [email protected]

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6055


cichlid fish. J. Neuroendo-crinol. 14(8): 657-65.

Pearse, A.G.E (1972): Histochem istry. Theoretical and ap-plied. 2nd Ed. Churlchill, London.

Peter, R. E.; Yu, K.; Marchant, T. A. and Rosenblum,P.M. (1990): Direct neural regulation of the teleost adenohypophy-sis. J. Exp. Zool. (256) 4: 84 – 89.

Peterson, M.S.; Brown-Peterson, N.J. and McDonald, J.L. (2004): Reproduction in non-native environments: estab-lishment of the Nile Tilapia Oreochromis niloticus in coastal Mississippi water-sheds. Copeia 2004:842-849.

Peute, J.; De Leeuw, R.; Goos, H.J. and Van Oordt, P.G. (1984): Ultrastucture and immunola-baling of gonadotrops and thyrotrops in the pituitary of the African catfish, Clarias lazera. Cell.Tiss. Res., 238: 95 - 103.

Rizkalla, W. (1963): A comparative study of the pituitary gland of Tilapia nilotica L. and Mugil capito L., Ain Shams Bull. 9: 177 – 211.

Sage, M. and Bern, H.A. (1971): Cytophysiology of the teleost pituitary. International Re-

view of Cytology 31: 339 - 376.

Sanchez cala, F.; Portillo, A.; Mart´in del Rio, M.P. and Mancera, J.M. (2003): Im-munocytochemical characte-rization of adenohypophy-seal cells in the greater weever fish (Trachinus dra-co). Tissue & Cell 35: 169 – 178.

Schreibman, M.; Leatherland, J. F. and McKeown, B. A. (1973): Functional morphology of te-leost pituitary gland. Am. Zool. 13:719 – 742.

Schreibman, M.; Pertschuck, L. P.; Rainford, E. A.; Margolis-Kazan, H. and Gelber, S. J. (1982): The histochemical localization of steroid binding sites in the pituitary gland of a teleost (the platyfish). Cell. Tissue Res. 226: 523 - 530.

Takashima, F. and Hibiya, T. (1995): An atlas of fish mor-phology. Normal and patho-logical features. Kodansha, Tokyo, pp. 128 – 153.

Villaplana, M.; García-Ayala, A.; García-Hernández, M. P. and Agulleiro, B. (1997): On-togeny of immunoreactive somatolactin cells in the pi-tuitary of gilthead sea bream (Sparus aurata L., Teleos-tei). Anat. Embryol. 196: 227 – 234.

Wai-Sum, O. and Chan, S.T.H. (1974): A cytological study on the structure of the pitui-tary gland of Monopterus al-bus (Zuiew). Gen. Comp. Endocrin., 24: 208 - 222.

Weltzien, F.; Andersson, E; Ander sen, O; Tabrizi, K.S and Norberg, B. (2004): The brain – pituitary – gonad axis in male teleost, with special emphasis on flatfish (Pleu-ronectiformes). Comparative Biochemistry and Physiology Part A 137: 447– 477.

Weltzien, F.: Norberg, B.: Helvik, J.V.: Andersen. O: Sawnson, P. and Andersson, E(2003): Identification and localization of eight distinct hormone-producing cell types in the pituitary of male Atlantic ha-libut (Hippoglossus hippog-lossus L.). Comparative Bio-chemistry and Physiology Part A 134: 315-327.

Yoakim, E.G. (1971): Seasonal var iations in the pituitary gland and gonads of the Nile cat-fish (Synodontus schall) in relation to its reproductive cycle. Ph.D. Thesis. Faculty of Science.Ain Shams Uni-versity.

Yoshiura, Y.; Suetake, H. and Aida, K. (1999): Duality of gonado-tropin in a primitive teleost,

Japanese eel (Anguilla japo-nica). Gen. Comp. Endocri-nol. 114: 121–131.

________________ Correspondence: e-mail [email protected]

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6056


Fig(1): Section of proximal pars distalis of the pituitary gland of mature female Nile tila-pia during spring showing: Gonadotrops (g), Vacuoles (V), Capsule (C), Blood vessels (BV). Aldehyde thionin- periodic acid schiff -orange G (Ath-PAS-OG) X1000.

Fig (2):Section of pituitary gland of mature female Nile tilapia during spring showing: Rostral pars distalis (RPD), Proximal pars distalis (PPD), Pars intermedia (PI), Neurohy-pophysis (NH). H&E. X100.

Fig (3):Section of rostral pars distalis of the pituitary gland of mature male Nile tilapia during spring showing: Adenohypophyseal cells arranged in cords, Acidophilic cells (A), Basophilic cells (B). H&E. X 400.

Fig (4):Section between rostral pars distalis and proximal pars distalis of the pituitary gland of mature male Nile tilapia during spring showing: Lactotrops (PRL), Somatotrops (S), Gonadotrops (g), cavity containing orange G positive colloid-like material (arrow), Periodic acid schiff technique - orange G – light green. X1000.

Fig (5):Section of proximal pars distalis and pars intermedia of the pituitary gland of ma-ture male Nile tilapia during spring showing: more extensive interdigitation between the neurohypophysial tissue and pars intermedia (PI). Periodic acid schiff technique - orange G – light green (PAS – OG-LG). X100.

Fig (6):Section of pars intermedia of the pituitary gland of mature male Nile tilapia dur-ing summer showing: (PRL): isolated Lactotrops (orange G positive) under capsule in pars intermedia, Gonadotrops (aniline blue positive) (g), Capsule. Azocarmine-aniline blue-orang G. X1000.

Fig (7):Section of rostral pars distalis of the pituitary gland of mature male Nile tilapia during summer showing: Lactotrops (orange G positive) (PRL), Degranulated lactotrops (d), Azocarmine-aniline blue-orange G. X1000.

Fig (8):Section of the rostral pars distalis of the pituitary gland of mature male Nile tila-pia during summer showing: Corticotrops appeared deeply stained (C) and others were degranulated (arrow). Lead heamatoxyline- periodic acid Schiff (PbH- PAS). X400.

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6057


Fig(1): Section of proximal pars distalis of the pituitary gland of mature female Nile tila-pia during spring showing: Gonadotrops (g), Vacuoles (V), Capsule (C), Blood vessels (BV). Aldehyde thionin- periodic acid schiff -orange G (Ath-PAS-OG) X1000.

Fig (2):Section of pituitary gland of mature female Nile tilapia during spring showing: Rostral pars distalis (RPD), Proximal pars distalis (PPD), Pars intermedia (PI), Neurohy-pophysis (NH). H&E. X100.

Fig (3):Section of rostral pars distalis of the pituitary gland of mature male Nile tilapia during spring showing: Adenohypophyseal cells arranged in cords, Acidophilic cells (A), Basophilic cells (B). H&E. X 400.

Fig (4):Section between rostral pars distalis and proximal pars distalis of the pituitary gland of mature male Nile tilapia during spring showing: Lactotrops (PRL), Somatotrops (S), Gonadotrops (g), cavity containing orange G positive colloid-like material (arrow), Periodic acid schiff technique - orange G – light green. X1000.

Fig (5):Section of proximal pars distalis and pars intermedia of the pituitary gland of ma-ture male Nile tilapia during spring showing: more extensive interdigitation between the neurohypophysial tissue and pars intermedia (PI). Periodic acid schiff technique - orange G – light green (PAS – OG-LG). X100.

Fig (6):Section of pars intermedia of the pituitary gland of mature male Nile tilapia dur-ing summer showing: (PRL): isolated Lactotrops (orange G positive) under capsule in pars intermedia, Gonadotrops (aniline blue positive) (g), Capsule. Azocarmine-aniline blue-orang G. X1000.

Fig (7):Section of rostral pars distalis of the pituitary gland of mature male Nile tilapia during summer showing: Lactotrops (orange G positive) (PRL), Degranulated lactotrops (d), Azocarmine-aniline blue-orange G. X1000.

Fig (8):Section of the rostral pars distalis of the pituitary gland of mature male Nile tila-pia during summer showing: Corticotrops appeared deeply stained (C) and others were degranulated (arrow). Lead heamatoxyline- periodic acid Schiff (PbH- PAS). X400.

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6058


Fig (9):Section of the proximal pars distalis of the pituitary gland of mature female Nile tilapia during summer showing: Somatotrops (S), Gonadotrops (g). Azocarmine-aniline blue-orange G. X1000.

Fig (10):Section of the proximal pars distalis of the pituitary gland of mature male Nile tilapia during spring showing: Somatotrops (S), Gonadotrops (g), Neurohypophysis (NH), Pars intermedia (PI). Aldehyde thionin-periodic acid schiff -orange GX100.

Fig (11):Section of the proximal pars distalis of the pituitary gland of mature female Nile tilapia during spring showing: Gonadotrops (g), Somatotrops (S). Aldehyde fuchsin-orange G-light green. X1000.

Fig (12):Section of the proximal pars distalis of the pituitary gland of mature female Nile tilapia during spring showing: Gonadotrops (g). Aldehyde fuchsin-orange G-light green X1000.

Fig (13):Section of rostral pars distalis and proximal pars distalis of the pituitary gland of mature male Nile tilapia during summer showing: Gonadotrops (g), Thyrotrops (T), So-matotrops (S), Lactotrops (PRL). Aldehyde thionin-periodic acid schiff -orange G. X100.

Fig (14):Section of pars intermedia of the pituitary gland of mature female Nile tilapia during summer showing: Melanotrops (M), Somatolactotrops (SL), Gonadotrops (g), Neurohypophysis (NH). Lead haematoxyline- periodic acid schiff (PbH-PAS). X400.

Fig (15):Section of the pars intermedia of the pituitary gland of mature female Nile tila-pia during spring showing: Neurohypophysis contained aldehyde thionin positive fibers. (NH), Neurosecretion positive to orange G (NS), Somatolactotrops (SL), Melanotrops (M). Aldehyde thionin-periodic acid schiff -orange G. X400.

Fig (16):Section of pars intermedia of the pituitary gland of mature male Nile tilapia dur-ing summer showing: Melanotrops (M), Somatolactotrops (SL), Blood vessels in the Neurohypophysis (arrow). Lead haematoxyline- periodic acid schiff (PbH-PAS). X1000.

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6059


Fig (9):Section of the proximal pars distalis of the pituitary gland of mature female Nile tilapia during summer showing: Somatotrops (S), Gonadotrops (g). Azocarmine-aniline blue-orange G. X1000.

Fig (10):Section of the proximal pars distalis of the pituitary gland of mature male Nile tilapia during spring showing: Somatotrops (S), Gonadotrops (g), Neurohypophysis (NH), Pars intermedia (PI). Aldehyde thionin-periodic acid schiff -orange GX100.

Fig (11):Section of the proximal pars distalis of the pituitary gland of mature female Nile tilapia during spring showing: Gonadotrops (g), Somatotrops (S). Aldehyde fuchsin-orange G-light green. X1000.

Fig (12):Section of the proximal pars distalis of the pituitary gland of mature female Nile tilapia during spring showing: Gonadotrops (g). Aldehyde fuchsin-orange G-light green X1000.

Fig (13):Section of rostral pars distalis and proximal pars distalis of the pituitary gland of mature male Nile tilapia during summer showing: Gonadotrops (g), Thyrotrops (T), So-matotrops (S), Lactotrops (PRL). Aldehyde thionin-periodic acid schiff -orange G. X100.

Fig (14):Section of pars intermedia of the pituitary gland of mature female Nile tilapia during summer showing: Melanotrops (M), Somatolactotrops (SL), Gonadotrops (g), Neurohypophysis (NH). Lead haematoxyline- periodic acid schiff (PbH-PAS). X400.

Fig (15):Section of the pars intermedia of the pituitary gland of mature female Nile tila-pia during spring showing: Neurohypophysis contained aldehyde thionin positive fibers. (NH), Neurosecretion positive to orange G (NS), Somatolactotrops (SL), Melanotrops (M). Aldehyde thionin-periodic acid schiff -orange G. X400.

Fig (16):Section of pars intermedia of the pituitary gland of mature male Nile tilapia dur-ing summer showing: Melanotrops (M), Somatolactotrops (SL), Blood vessels in the Neurohypophysis (arrow). Lead haematoxyline- periodic acid schiff (PbH-PAS). X1000.

J. Vet. Anat. Vol 4 No 2, (2011) 39 - 6060


Fig (17):Section of pars intermedia of the pituitary gland of mature male Nile tilapia dur-ing summer showing: Melanotrops (M), Somatolactotrops (SL), Neurohypophysis (NH). Azocarmine-aniline blue-orange G.X1000. Fig (18):Section of proximal pars distalis of the pituitary gland of mature male Nile tilapia during winter showing: Gonadotrops (g), Blood sinusoids in the Neurohypophysis (ar-row). Lead haematoxyline- periodic acid schiff (PbH-PAS). X1000.

Fig (19):Section of proximal pars distalis of the pituitary gland of mature female Nile ti-lapia during winter showing: Gonadotrops (g), Somatotrops (S), Thyrotrops (T). Alde-hyde fuchsin-orange G-light green. X400. Fig (20):Section of pars intermedia of the pituitary gland of mature female Nile tilapia during winter showing: Melanotrops (M), Somatolactotrops stained with both PbH and PAS (SL). Lead haematoxyline- periodic acid schiff (PbH-PAS). X1000.

Seasonal Histology of the Testes of Nile Tilapia (Oreochromis niloticus)

El-Sakhawy, M.A; El-Saba, A.A; Abd Rabou, M.I; El-Shammaa, M.A; and Hussein, S.H Department of Cytology and Histology, Faculty of Veterinary Medicine Cairo University. ______________________________________________________________________ With 12 figures received August, accepted for publication September 2011

Abstract In the present research, the histolo-gy of the testes of Nile tilapia were done on 56 males sexually mature Nile tilapia fish collected monthly from the River Nile at Giza over the period from September 2009 to Au-gust 2010. The testis of the Nile ti-lapia during the spring, summer and autumn seasons was surrounded by very thin tunica albuginea. The tes-ticular capsule extended inside the testis to give connective tissue sep-ta. The bulk of the testis was com-posed of seminiferous tubules. These tubules were surrounded by interstitium. The tubules filled with germinal cysts; contained germinal cells at different stages of develop-ment and surrounded by cytoplas-mic processes of Sertoli cells. The spermatogenic cells were sperma-togonia type A and type B, primary spermatocytes, secondary sperma-tocytes, spermatids and spermato-

zoa. The interstitium filled the inter-tubular spaces and was composed mainly of fine collagenous connec-tive tissue which contained abun-dant Leydig (interstitial) cells and blood capillaries. The testis during winter appeared evacuated from the spermatozoa with no cystic ar-rangement of the germinal cells. The testis showed different degrees of vacuolation. The tubular lumen contained residual sperms. The va-cuoles appeared in the Sertoli cells. Phagocytic cells were observed in close association of the basement membrane of Sertoli cells. Key words Oreochromis niloticus, testis Introduction Nile tilapia belongs to genus Oreochromis. This species is natu-rally distributed in the Nile River as well as most parts of African Rivers

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Seasonal Histology and Histochemistry of the Adenohypophysis of Nile Tilapia