Nematology, 2009, Vol. 11(2), 161-169

Redescription of Butlerius butleri Goodey, 1929 (Nematoda:Diplogastridae) from South Korea

Irfan AHMAD 1,∗, Gaurav K. SINGH 1, Il-Kweon YEON 2 and Chung-Don CHOI 2

1 Section of Nematology, Department of Zoology, Aligarh Muslim University, Aligarh 202002, India2 Sung-Ju Fruit Vegetable Experimental Station, 635 Daechen, Daega, Sungju, Kyongbuk, South Korea

Received: 20 February 2008; revised: 19 May 2008Accepted for publication: 20 May 2008

Summary – The type species of the genus Butlerius, viz., B. butleri Goodey, 1929, is redescribed and illustrated from specimenscollected in South Korea. Additional information is provided for the cuticle, stoma structure, female reproductive system and the malecaudal region. The Korean population is 1336-1857 μm long, a = 33.9-43.5, b = 5.41-6.34, c = 3.38-4.20, c′ = 14.13-19.0 and V =40-45%. Males have spicules 39-49 μm long and a gubernaculum 25-33 μm long. There are nine pairs of genital papillae, three pairsprecloacal and six pairs postcloacal. The v5,6,7 clusters are widely separated, one group situated just posterior to the phasmids and theother group at level of pd. Although there are some differences in morphometrics as compared with the type population, the speciesis easily identified by the similarities in the structure of the stoma, pharynx, spicules and gubernaculum. Butlerius singularis and B.filicaudatus are proposed as synonyms of the type species.

Keywords – Butlerius filicaudatus n. syn., Butlerius singularis n. syn., morphology, morphometrics, new synonym, taxonomy, typespecies.

The genus Butlerius Goodey, 1929 was proposed withB. butleri Goodey, 1929 as type species. It is charac-terised by a large and spacious buccal cavity, long se-tose labial sensilla, stegostom with a thorn-like tooth, am-phidelphic reproductive system, narrow curved spiculesand gubernaculum ca two-thirds the spicule length. Tay-lor (1964) described B. monhystera Taylor, 1964 witha single anterior ovary. Based on the absence or reduc-tion of the posterior gonad, Andrássy (1984) proposedMonobutlerius for three monodelphic species and syno-nymised Butleroides Lordello & Zamith, 1959 and But-leriellus Meyl, 1960 with Butlerius. Ebsary (1986), un-aware of the creation of Monobutlerius Andrássy, 1984,proposed the genus Parabutlerius for the monodelphicspecies. Sudhaus and Fürst von Lieven (2003) synony-mised Monobutlerius and Parabutlerius (monodelphic)and Mesodiplogasteroides Khera, 1969 (amphidelphic)with Butlerius and accepted Andrássy’s (1984) synonymyof Butleroides and Butleriellus. Of the 15 species listedby these authors, four are monodelphic. Goodey’s (1929)description of B. butleri was based on five females, twomales and two juveniles collected from rotting bananaroots. Specimens collected from South Korea, also from

∗ Corresponding author, e-mail: ahmadirfi@gmail.com

rotting plant material, showed a striking resemblance tothe type species so it was decided to examine the typematerial and provide a more detailed description of thespecies.

Materials and methods

Nematodes were isolated by placing chopped decayingplant material in a small coarse sieve lined with tissuepaper which was then placed in a Petri dish containingwater. The sieve was placed on rubber supports and thewater just touched the bottom of the sieve. After 24 h thewater from the Petri dish was placed in centrifuge tubesand the nematodes were concentrated by centrifugation.The specimens were killed and fixed in hot Seinhorst’sFA (4 : 1) for 24 h and then transferred to glycerin-alcohol(5 : 95 parts) and kept in a desiccator for slow dehydration.Permanent mounts were made in glycerin employingthe wax ring technique. All morphological observations,drawings and photographs were made using an OlympusBX 50 DIC microscope.

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Butlerius butleri Goodey, 1929= B. filicaudatus Adam, 1930 n. syn.

= B. singularis Lordello & Zamith, 1959 n. syn.(Figs 1-3)

MEASUREMENTS

See Table 1.

DESCRIPTION

Female

Body long and slender, tapering only very slightly an-teriorly, but more so posterior to rectal region. Trans-verse striations very faint, with equally spaced, finedot-like punctations. Lateral fields with three very finelines (not visible in all specimens and mostly occludedby the underlying subcuticular punctations); longitudi-nal striations not discernible. Subcuticle (hypodermis)with prominent, large dot-like punctations appearing intransverse and diagonal lines. Lip region continuous withbody contour, lips low, fused. Single, horn-shaped, se-tose papilla present on each lip. Stoma longer thanbroad. Cheilostom spacious, barrel-shaped, cheilorhab-dions arched inwards anteriorly. At about base of lip re-gion, cheilorhabdions with ledge-like outgrowth forminga smooth paracheilostomal ring just posterior to ante-rior end of cheilostom. Cheilorhabdial flaps six, eitherarched inwards over stoma opening or straightened toreveal an open stoma. Gymnostom broader than long,anisotopic, dorsal wall shorter than subventrals, lackingarmature. In some specimens gymnostom showing veryfaint longitudinal markings. Broad hyaline band-like lig-ament connecting cheilo- and gymnorhabdions. Stegos-tom anisomorphic, dorsal metastegostom with a medium-sized tooth, right subventral with a very small tooth, left asmooth-edged plate. Dorsal pharyngeal gland duct open-ing on dorsal tooth. Pharynx in two parts, corpus muscu-lar, of uniform diam. except at posterior end where ex-panding, slightly forming a median bulb. Corpus lumenprominently sclerotised. Posterior pharynx with a rela-tively muscular isthmus, very gradually expanding pos-teriorly. Dorsal gland nucleus usually prominent, locatednear base of pharynx. Nerve ring surrounding isthmusimmediately posterior to median bulb. Excretory poreslightly posterior to nerve ring with a prominent ampullaand a single renette cell. Cardia well developed, consist-ing of three flaps, one dorsal and two ventrosublateral.Intestine composed of dark granulated cells with promi-nent nuclei. Reproductive system amphidelphic, reflexed.

Ovaries large, terminating less than one vulval body diam.from vulva. Oocytes with large nuclei, arranged in doublerow in germinal zone and single row in maturation zone.Spermatheca not demarcated externally, usually with finewavy, thread-like, sclerotised structures sometimes visi-ble in adjacent oviduct. Glandular part of uterus long,made up of large cells and narrow lumen. Muscular partsmaller and narrower with its inner wall sclerotised dorso-laterally. Four large unicellular glands opening into uteri,two in anterior part and two in posterior part muscularpart. Vagina narrow, tubular, ca one-third of correspond-ing body diam. long. Vulval opening small, pore-like,flush with body contour or sometimes depressed, usuallyradially ridged. Tail long filiform, whip-like. Phasmidialopening large, sclerotised, with prominent duct leadinginto interior of tail tissue.

Male

Similar to female but slightly smaller in size and withfour cephalic setae in addition to six labial setae. Stomastructure and position and size of amphidial openings sim-ilar to female. Reproductive system monorchic, testis re-flexed. Sphincter present in mid-region of vas deferens.Spicules long, slender and curved. Capitulum flat ante-riorly with circular outline, shaft small and blade longand narrow. Gubernaculum long, ca two-thirds of spiculelength. Proximal part narrow, curved, handle-like; dis-tal part with sleeve. Distal tip of gubernaculum withtwo small, laterally directed, barb-like processes. Geni-tal papillae comprising nine pairs, three pairs precloacaland six pairs postcloacal. Genital papillae formula: v1, v2,v3d / v4, ad, ph, v5,6,7, pd. Two v5,6,7 clusters greatlyseparated from each other with left subventral group justposterior to phasmids and right subventral group at levelof pd. Each group with two small (v5,6) and one large (v7)papilla. Pair v7 of posterior group sometimes slightly pos-terior to pd. Anterior cloacal lip large, lobe-like, protrud-ing posteriorly with single prominent papilla. Posteriorcloacal lip slightly thickened, with single pair of smallerpapillae. Tail similar to female, long filiform, whip-like.Phasmidial opening large, sclerotised, similar to female.

HABITAT AND LOCALITY

Collected from rotting plant material at the Song-JuFruit Vegetable Experimental Station, Daechen, SouthKorea.

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Fig. 1. Butlerius butleri Goodey, 1929 from South Korea. A: Entire female; B: Entire male; C-E: Stoma (female); F: Female reproductivetract (anterior); G: Pharyngeal region (female); H: Uterine glands; I: Female posterior region; J: Male posterior region; K: Lateralfield; L: Spermatheca showing fine thread-like structures; M: Spicule; N: Gubernaculum.

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Fig. 2. Butlerius butleri Goodey, 1929 from South Korea. A-D: Stoma (female); E: Corpus (female); F: Post-corpus (female); G:Uterine region showing glands; H: Intact prey in intestine; I: Spicules of prey in intestine; J: Sclerotisation in uterus; K: Spicules andgubernaculum; L: Male posterior region showing caudal papillae, phasmid (arrow), cuticular and subcuticular punctations. (Scalebars: A-H, J-L = 10 μm; I = 20 μm.)

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Fig. 3. Butlerius butleri Goodey, 1929. A-F from South Korea. A: Cuticular punctations (female); B: Subcuticular punctations(female); C: Buccal cavity showing band (arrow) between cheilostom and gymnostom (male); D: Isthmus region showing excretorysystem (female); E: Spermatheca showing fine thread-like structures (arrows); F: Male posterior region showing sphincter. G-I: Typespecimens. G: Spicules and gubernaculum; H: Spicules of prey in intestine (female); I: Corpus and isthmus (female). (Scale bars:A-I = 10 μm.)

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Table 1. Morphometrics of Butlerius butleri Goodey, 1929 from South Korea. All measurements are in μm and in the form: mean ±standard deviation (range).

Character Female Male

n 8 7L 1586 ± 170 (1335-1857) 1404 ± 169.5 (1197-1641)L′ 1176 ± 131.5 (940-1338) 1032 ± 118.5 (849-1164)a 41.4 ± 4.6 (33.9-46.5) 45.4 ± 1.7 (43.2-48.1)a′ 29.7 ± 2.7 (25.8-33.1) 33.5 ± 2.4 (30.6-36.7)b 5.7 ± 0.3 (5.4-6.34) 5.6 ± 0.3 (4.9-5.8)b′ 4.2 ± 0.2 (3.8-4.5) 4.1 ± 0.3 (3.4-4.4)c 3.7 ± 0.3 (3.4-4.2) 3.4 ± 0.2 (3.2-3.7)c′ 17.4 ± 1.6 (14.1-19.0) 14.6 ± 0.9 (13.8-16.4)V 42.6 ± 1.5 (39.8-44.8) –Max. body diam. 40 ± 7.5 (28-51) 31 ± 2.9 (27-37)Lip diam. 20.0 ± 1.5 (18.0-22.0) 18.5 ± 1.5 (17.0-22.0)Length of stoma 26.5 ± 1.5 (24.5-27.5) 24.5 ± 2.0 (22.0-27.5)Corpus 151 ± 9.6 (133-165) 140 ± 10.5 (129-156)Postcorpus 128 ± 10.0 (112-139) 113 ± 12.0 (94-133)Pharynx 279 ± 19.0 (246-301) 253 ± 21.5 (215-288)Excretory pore from anterior end 167 ± 11.5 (152-187) 164 ± 9.5 (154-180)Nerve ring from anterior end 156 ± 10.5 (141-172) 144 ± 11.0 (125-163)Median bulb (diam.) 24.5 ± 2.5 (20.0-27.5) 20.5 ± 2.0 (18.0-24.5)Basal bulb (diam.) 25.0 ± 3.0 (20.0-29.5) 20.0 ± 2.5 (18.0-24.5)Cardia 7.5 ± 0.5 (7.0-9.0) 7.5 ± 0.7 (7.0-9.0)Anterior gonad 209 ± 27.5 (162-251) –Posterior gonad 199 ± 34.5 (137-263) –Vulval body diam. 40.0 ± 7.5 (28.5-50.5) –Vulva-anus distance 481 ± 67.5 (361-570) –Rectum 33.0 ± 2.5 (29.5-36.5) –Tail 481 ± 67.5 (361-570) 406 ± 55.0 (336-503)Anal/cloacal body diam. 25.0 ± 3.0 (21.0-28.5) 27.5 ± 2.5 (24.0-30.5)Testis – 634 ± 74.5 (486-726)Spicules – 43.5 ± 3.5 (38.5-48.5)Gubernaculum – 29.5 ± 2.5 (24.5-32.5)

L′ = length from head to anus.a′ = L′ divided by max. body diam.b′ = L′ divided by length of pharynx.

VOUCHER MATERIAL

One female and two males on slide Butlerius butleri/6at Rothamsted Research, Harpenden, UK.

ECOLOGY AND FEEDING

As with several other diplogastrid species, B. butlerioccurs in a saprobiotic habitat of decaying plant material.Butlerius micans Pillai & Taylor, 1968 occurred in sewagetreatment plants and B. macrospiculum Hunt, 1980 infrass from a rotting log, while B. monhystera Taylor,1964 and B. macrogubernaculum Chitamber, 1990 were

found in nurseries where the soil is usually enrichedwith compost. A study of the gut contents revealed theremains of spicules in the posterior part of the intestinein two specimens (Fig. 2I) and an entire nematode in theanterior part in another specimen (Fig. 2H). Examinationof the type specimens revealed the presence of spiculesin the gut of two specimens (Fig. 3H). While indicatingthe predatory habit of the species it also shows that theprey is engulfed whole as in many mononchs (Bilgramiet al., 1986). Prey is not known to be swallowed wholeby diplogastrids, Lordello and Zamith (1959) describingB. singularis (= B. butleri see below) as a voracious

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predator and a cannibal, cutting or tearing the nematodesit fed upon. Furthermore, we are inclined to believe thatthe spicules would not normally be ingested with thebody contents and so the prey must have been swallowedwhole. Adam’s (1930) observation that the buccal cavityof B. filicaudatus (= B. butleri see below) was filled withbacteria does not preclude a predatory behaviour. The fewstudies on the feeding behaviour of Butlerius species haverevealed that B. monhystera and B. micans are primarilypredatory in habit although the latter can also be grown inan amoeba-bacteria culture (Taylor, 1964; Pillai & Taylor,1968). Further, both these species fed on other nematodesby drawing them into the buccal cavity either from theanterior or posterior end or by grasping them at any otherpoint. In the buccal cavity the body wall is ruptured andthe contents sucked in. Studies on preserved specimens,however, preclude the possibility of a firm conclusion onthe feeding habits of the species. Hence, although thepredatory nature of B. butleri may be established, it cannotbe said with certainty whether it is an obligate predatorand whether it always engulfs prey whole.

REMARKS

The type slide of B. butleri, marked 25/1/2 and re-mounted in 1974, has specimens collected from rottingbanana stem (root in literature). Besides the type speciesseveral other (mostly unidentifiable) nematodes are alsopresent. Goodey (1929) mentions finding five females,two males and two immature females. On examination ofthe type slide we could account for five females, one maleand two juveniles. All specimens are greatly flattened andin a very poor state, yet still recognisable. We are in littledoubt that the Korean population is conspecific with thetype although there are some differences in the morpho-metrics and morphology.

The values of most morphometric characters overlap,except for the smaller a ratio (18.3-23.3) and largerV ratio (58-64) in the type population. All the typespecimens are greatly flattened and this could be onereason for their smaller a ratio. Further, the very longfilamentous tails often break thereby reducing body lengthand affecting ratios. Notwithstanding these differences,however, the labial setae, the structure of the stomaand pharynx, position of nerve ring and the shape andsize of spicules and gubernaculum provide sufficientevidence to confirm the identity of the Korean population.Even the tiny lateral projections at the distal tip ofgubernaculum are present. Furthermore, the prominentsubcuticular punctations, though not reported by Goodey

(1929), are clearly visible on some parts of the body intwo of the type specimens.

Certain structures reported in the Korean population,such as the paracheilostomal ring, the uterine glands, thesphincter in males and the cuticular punctations are, withthe exception of the first structure, not always easily vi-sualised. There is also a possibility that Goodey’s spec-imens, which were preserved in “strong alcohol”, mayhave experienced deleterious effects that have obscuredsome fine details. Goodey (1929) described nine pairs ofgenital papillae in three groups – Ia, b and c ventrolateralof which Ia is pre-cloacal; IIa, b and c the usual three pairsforming a compact group, and IIIa, b and c of which IIIa isprecloacal and IIIc is dorsolateral. The description of thegenital papillae with just two males, which, as mentioned,were “rather flattened” and “not as clear in respect to thesestructures”, needs to be clarified. By comparing the po-sitions of the genital papillae their arrangement can beunderstood in the light of the genital papillae formula ofSudhaus and Fürst von Lieven (2003). Ia is most probablythe displaced v4, Ib is ad and Ic is one of the 5,6,7 groupadjacent to the phasmid while IIa,b,c is the second of the5,6,7 group at level of pd. IIIa is v3d and IIIc is pd bothof which are in conformity but IIIb most probably repre-sents the phasmid close to the anterior 5,6,7 group. WhatGoodey (1929) mentions as possibly another ventrolat-eral pair at the level of the spicule head coincides withthe position of v2. This would make ten pairs of papillaewith one pair, the anteriormost v1 still unaccounted for.The discrepancy in numbers appears to have arisen be-cause of the anterior-posterior segregation of the v5,6,7groups which were considered as separate papillae. This,coupled with the excessive flattening, may have resultedin the unusual configuration of the genital papillae in thetype population.

Lordello and Zamith (1959) described B. singularisLordello & Zamith, 1959 from around papaya roots. Onecharacteristic feature of the species was the ‘paraphas-mid’, an unpaired structure in the tail region of both malesand females. The paraphasmid had a thick-walled ampullaand a short duct not connected to any structure. A sin-gle such structure, situated laterally, is highly improbableand militates against the bilateral symmetry plan of or-ganisation. This structure compares well with the phasmidof our population where the opening is large and sclero-tised and has a prominent duct leading into the interior.We therefore strongly believe that the paraphasmid de-scribed by Lordello and Zamith (1959) in B. singulariscorresponds to the phasmid. Butlerius singularis was dif-

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ferentiated from B. butleri by a longer body and longerand thicker cephalic setae with a globular secretion at theirbase (Lordello & Zamith, 1959). Body length can be ex-tremely variable, more so in different geographical iso-lates, and is therefore not a reliable distinguishing char-acter. The size and thickness of the labial setae have tobe considered very carefully, bearing in mind that onlyslight variations may be expected in the size of these struc-tures and the effects of the strong alcohol fixative on them.Many features of B. singularis strongly resemble thoseof B. butleri. The lip region, the buccal cavity, the pha-rynx, position of nerve ring and the structure and shapeof spicules and gubernaculum are almost identical. Thearrangement of the papillae has been described as irregu-lar. In their Figure 1, Lordello and Zamith (1959) mentionone preanal ventrolateral pair (corresponding to v2) andtwo postanal pairs: one pair lateral (corresponding to ad)and one pair dorsolateral (corresponding to pd). Also de-picted on the diagram, but not mentioned in the text, is onepostanal pair (corresponding to v4) and the v5,6,7 clusterjust posterior to the phasmid (the anterior group as de-scribed in our population). We are, therefore, reasonablysure that B. butleri and B. singularis are conspecific; thelatter being proposed as a junior synonym herein.

Butlerius filicaudatus Adam, 1930 also resembles B.butleri in the shape of the lip region, structure of thebuccal cavity and pharynx, position of the nerve ring andthe shape and size of the spicules and gubernaculum. Itwas differentiated from B. butleri by a longer and moreslender body and longer female gonad. Body length mayvary in geographical isolates and female gonad lengthmay show seasonal variation. As already mentioned,previous flattening of the specimens possibly resultedin the smaller ratio a in the type specimens (Goodey,1929). Adam (1930) made some interesting and pertinentcomments on some features of B. butleri. The absenceof a membranous ring between the gymnostom and thestegostom was attributed to contraction of the ring infixed specimens. More specifically, we believe it may havebeen because of improper fixation as our fixed specimensclearly show this structure. As regards the labial papillae,each described as having two bristles in B. filicaudatus,this is quite unusual though not improbable. The onlypapillae known to have bifurcate tips are the v5,6,7 groupof caudal papillae in species of Mononchoides (Goodrichet al., 1968; Tahseen et al., 1992). Regarding the lips,Goodey (1929) probably erred in mentioning that lipsare absent and Adam (1930) was also in error in statingthat the conus consisted of six moveable lips. The six

cheilorhabdial plates extend beyond the labial contour andarch over the stoma opening forming a conoid structure.The lips occur peripherally to this structure. The plates,however, can be splayed outwards to varying degreeswhen the stoma is open (Fig. 2). Goodey (1929) reportedone subventral tooth and we also observed one very tinydenticle on the right subventral plate, while two subventralteeth were described for B. filicaudatus. The armatureon the subventral plates in Butlerius species is quitevariable and each plate may have one denticle each (B.micans) or one plate may have a denticle and the other adenticulate ridge (B. monhystera and B. macrospiculum)or a single denticle on one (right) subventral plate (B.butleri). The subventral plates are arched inwards towardsthe stoma cavity (Fürst von Lieven & Sudhaus, 2000)and may also give a false impression of teeth in opticalsection view. In specimens of B. micans collected inIndia we have observed a denticulate ridge on the leftsubventral plate and a tooth on the right subventral plate(unpubl.). Notwithstanding some minor differences, thesimilarities of B. butleri and B. filicaudatus are too strongto permit separation of the species. Butlerius filicaudatusis, therefore, considered a junior synonym of B. butleri.

Acknowledgements

We thank Prof. Brian Kerry and Ms Janet Rowe formaking available the type slide of B. butleri from Rotham-sted Research, Prof. W. Sudhaus for some early literatureon Butlerius spp. and some German translation, Mr PabloGuerrero and Ms Gisela Teixeira of the University of Jaenfor the Portuguese translation, the Indian National ScienceAcademy (INSA), New Delhi and Aligarh Muslim Uni-versity (AMU), Aligarh, for the travelling grant and theKorean Science and Engineering Foundation (KOSEF)for financial support during the visit of the first author toSouth Korea.

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LORDELLO, L.G.E. & ZAMITH, A.P.L. (1959). Observacoessobre o genero “Butlerius” de nematodeos de vida livre.Revista Brasileira de Biologica 19, 177-182.

MEYL, A.H. (1960). Die freilebenden Erd- und Subwasserne-matoden (Fadenwurmer). In: Brohmer, P., Ehrmann, P. & Ul-mer, G. (Eds). Die Tierwelt Mitteleuropas, Vol. 1. Leipzig,Germany, Quelle & Meyer, 164 pp.

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SUDHAUS, W. & FÜRST VON LIEVEN, A. (2003). A phyloge-netic classification and catalogue of the Diplogastridae (Se-cernentea, Nematoda). Journal of Nematode Morphology andSystematics 6, 43-90.

TAHSEEN, Q., AHMAD, I., BILGRAMI, A.L. & AHMAD, W.(1992). A scanning electron microscope study on Monon-choides fortidens (Schuurmans-Stekhoven, 1951) Taylor &Hechler, 1966. Nematologica 38, 296-303.

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