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Trans. Br. mycol. Soc. 51 (3 and 4), 535-540 (1968)Printed in Great Britain

SOME AQUATIC HYPHOMYCETES FROM NIGERIA

ByS.O.ALASOADURA

Department of Botany, University of Ibadan, Nigeria

(With 3 Text-figures)

Aquatic hyphomycetes from eight streams in Nigeria were studied. Thespecies found include all those previously recorded for the country as belongingto known genera, and five species which are new records. Pyramidospora densasp.nov. is described and illustrated.

Studies of the aquatic hyphomycete spora of some streams in Nigeriawere made by Ingold (1956, 1959, 1961), who found the scum and foamsamples to be rich in spores of these fungi. Further, he placed the observedspores in three categories: firstly, those referable to described species:Actinospora megalospora Ing., Campylospora chaetocladia Ranzoni, Flagellosporacurvula Ing. and Triscelophorus monosporus Ing.; secondly, those referableto undescribed species ofknown genera: Actinospora, Campylospora, Claoariop­sis, Heliscus, Speiropsis, Tricladium, Trisulcosporium (Hudson & Sutton, 1964),and Varicosporium; finally, spores that could not be assigned to anydescribed genus. Some branched, septate spores with clamp connexionswere also figured.

Rich floras of aquatic hyphomycetes have also been reported from otherparts of Africa. Dixon (1959) examined scum and foam samples fromthree streams in Ghana and found a hyphomycete flora almost identicalwith that outlined for Nigeria by Ingold. Ten known species were foundin Sierra Leone by Le'-John (1965), who asserted that Campylosporachaetocladia, Flagellospora curvula and Triscelophorus monosporus are commonin tropical regions. Ingold (1958) recorded twelve known species fromUganda and seven from Rhodesia. In South Africa, Greathead (1961)found eighteen species growing on decaying leaves, all belonging toknown genera.

In Nigeria, there are two main seasons, a dry (November to March)and a rainy one (April to October). During the dry season, most of thestreams dry up completely, becoming flooded in the subsequent rainyseason; nevertheless, a few permanent fast-flowing streams are found.Observations of spores in foam and scum from some streams were madeperiodically during the past 3 years, especially during the rainy seasonssbut the report that follows is based on more detailed examination;conducted between January and June 1967.

Transactions British Mycological Society

SAMPLING STATIONS AND METHODS

Eight sites (all situated within go miles of Ibadan, Nigeria) on streamsmost of which are permanent (the others starting to flow early in therainy season) were included in the survey, but only five of these (Table I)were productive. Samples were collected from each stream. Whereveravailable, foam and scum samples were collected with a clean spoon andtransferred to McCartney bottles. Decaying and skeletonized submerged

Table I. Aquatichyphomycetes found in Nigeria

Locali tyA

Alaka Isasa Odoje Ogbe Ososi

Actinospora megalospora lug.Anguillospora longissima

(Sacc , & Sydow) Ing.Articulospora tetracladia Ing.Campylospora chaetocladia RanzoniFlagellospora curvula Ing.Lunulospora curvula Ing.Pyramidospora densa AlasoaduraTetracladium marchalianum D e Wild.T riscelophorus monosporus Ing.

oo

xox ox xx xx xx xx

x x x

x

x

x

. x, con idia attached to conidiophores a rising from subm erged decaying leaves; 0 , conidia infoam sample.

leaves were collected, usually on the up-stream side of barriers such asfallen branches in clear portions of the streams, and placed in cleanpolythene bags. All the samples were put in a cooled bag immediatelyafter collection and brought to the laboratory. The sample of foam wasallowed to settle in a refrigerator for a few hours, the clear supernatantliquid decanted, before drops of the suspension were examined under themicroscope. The leaf samples were washed thoroughly in tap water andplaced, submerged, in distilled water in dishes where they were stronglyaerated. These samples were scanned daily under the low power of themicroscope for a few days.

RESULTS

Foam and scum were found in only a few instances on the streams,especially at the beginning of the survey. Th e spores of the followingspecies were identified: Actinospora megalospora, Anguillospora longissima (Sacc.& Sydow) Ing. and Campylospora chaetocladia. Some species were found grow­ing on leafsamples. The fungi found and their distribution in the five streamsare given in Table I. Besides the known species, some were observedwhich could be assigned to known genera; one of these was particularlyabundant on decaying and skeletonized leaves collected from Isasa andOdoje. It is here described as a new species of Pyramidospora Nilsson.Finally, others could not be identified, but these are not considered here.

Aquatic hyphomycetes. S. O. Alasoadura 537

Pyramidospora densa sp. nov. (Fig. 1)Hyphomycete aquatica submersa, mycelio extenso. Hyphae hyalinae, ramosae,

septatae, 1-3 p latae. Conidiophorum germinat e foliis putrescentibus, hyalinum,simplex, septatum, 20-S0 plongum, I·S-3·0 platum, efferens unam sporam terminalem.Conidium (phialosporum) hyalinum, ramosum, septatum, forma trochleae ordinatum;axe principali duabus cellulis, Io-IS p longo, 4-6 plato; utraque ferens 3 ad 4projecturas, regulariter vel irregulariter insertas, essentialiter horizontales, projecturaunicellularis, 7-IS p longa, 4'0-7'S plata; raro projectura verticali ex superiorecellula axe itaque structura pyramidalis videtur ; conidium 29-37 platum.

HABITAT. In foliis putrescentibus dicotyledonearum plantarum in aquis dulcibus exIsasa River, Gbongan, Nigeria.

Typus, Herb IMI 129098 et U.I.B/S. 4.Typus ut siccata cultura, CBS 331/67 Baarn, Hollandia et U.I.B/C.129.

I----io 101'

Fig. I. Pyramidospora densa. (a)-(e) Conidiophores with conidia at various stages arrangedin a developmental series, as observed on unidentified submerged decaying leaf; (f)liberated conidia; (g) germinating conidia.

Nilsson (1962) erected the genus Pyramidospora for the single speciesP. casuarinae, which he described as ' a very strange type of aquatic fungus' •

A fungus (Fig. I), obviously belonging to this genus was found growingon submerged, unidentified, decaying and skeletonized leaves of somedicotyledonous plants collected in two streams. The mycelium within theleaf gives rise to simple, delicate conidiophores, 2C>--50 It long, 1'5-3 Itwide; with a single terminal phialide, &-12 It long, 2-4 It wide, narrowingnear its point of attachment to the conidium to an isthmus, 1-3 It longand about 1'0 It wide. The terminal conidium, branched, septate and

538 Transactions British Mycological Societyhyaline, consists of a short central axis and 6 to 8 lateral outgrowths. Thecentral axis is Io-IS P long, 4-6 p wide; consisting of two cells (one ontop of the other) which may be equal or unequal. The outgrowths, 3-4from each cell of the axis, lie more or less horizontally and point indifferent directions; each outgrowth is one-celled, 7-IS P long, 4-7'S/lwide. Occasionally, a vertical outgrowth may be found developed fromthe top part of the upper cell of the axis. The 'mature ' conidium measuresabout 29-37 P from the tip of one outgrowth to the tip of the oppositeone on the same 'wheel' of the 'pulley'. Conidia which have not attainedthe' mature' configuration, that is with 2-S outgrowths, may be detachedfrom their conidiophores.

40

E 30.s...c:~xCli 20

10

o 10 20 30 40Temperature (0C)

Fig. 2. P. densa. Vegetative growth in relation to temperature after 13 days. Eachpoint, mean of twelve measurements of colony diameter, three from each of fourcultures.

The development of the phialospore of P. casuatinae was described byNilsson (1962) and that of P. densa (Fig. I a-e) is very similar. A simpledelicate conidiophore grows out from the mycelium in the leaf anda rounded spore-initial is first formed, being clearly separated from theterminal phialide by an isthmus. The phialospore-initial soon becomesovoid and divided into two cells by a transverse septum. These two cellsconstitute the axis of the conidium. The first lateral outgrowth usuallydevelops from the basal cell and grows more or less horizontally; anotheroutgrowth, this time from the upper cell, begins to develop (in a hori­zontal direction) before the first attains full length. Other outgrowths,each one-celled, are formed in succession round the circumference of thetwo cells of the axis, so that 3 or 4 may be found on each in a matureconidium. Rarely, a vertical outgrowth arises from the upper cell of theaxis after or during the development of the lateral outgrowths.

In spite of the shape of the cell which bears the conidium and notwith­standing Nilsson's description of the spore of the type species as a phialo­spore, Prof. C. T. Ingold has expressed doubts about the phialospore natureof the conidium.

Aquatic hyphomycetes. S. o. Alasoadura 539Liberated conidia of P. densa germinate within 24 h when left in the

water at room temperature. Germ-tubes are produced from the tips ofoutgrowths; one or two usually develop from each conidium but sometimesfour germ-tubes are formed (see Fig. Ig).

Pure cultures obtained from single spores have been established onmalt agar. The colony, at first grey, turns medium grey after a few daysand the reverse side black, especially at the centre. The mycelium isslightly fluffy, composed of crowded, hyaline, septate, branched hyphae,about 0'6-3'7 p diam, The rate of extension growth shows an optimumaround 30° (Fig. 2).

(a)

(c)

j(b)

(d)

Fig . 3. P. densa. (o)- (c) Conidiophores with conidia at various stages arranged ina developmental series, as observed in pure culture on malt agar previously incubatedfor 15 days at 300 and then submerged in distilled water for 2 days at about 22

0;

(d) liberated conidia.

When slices of a colony (15 days old at about goO) were placed indistilled water in Petri dishes, conidia were produced abundantly.Nevertheless, these (Fig. g) were not identical with those developingnaturally on decaying leaves. The first-formed septum in the spore maybe almost vertical instead of transverse and many spores are liberated atthe 2-cell stage.

My thanks are due to Prof. C. T. Ingold for his interest in this studyand also to Prof. S. O. Esan and Mr P. O. Bodunrin of the Department ofClassics at the University for their invaluable help with the Latin diagnosis.

REFERENCES

DIXON, P. A. (1959) . Stream spora in Ghana. Trans. Br. my col. Soc. 42, 174-176.GREATHEAD, S. K. (1961). Some aquatic hyphoroycetes in South Africa. JI S. Afr. Bot.

27, 195-228.HUDSON, H.J. & SUTTON, B. C. (1964). Trisulcosporium and Tetranacrium, two new genera

of Fungi Imperfecti. Trans. Br, mycol. Soc. 47, 197-203.I NGOLD, C. T . (1956). Stream spora in Nigeria. Trans. Br. mycol. Soc. 39, 108-1 ro.

54° Transactions British Mycological SocietyINGOLD, C. T. (1958). Aquatic hyphomycetes from Uganda and Rhodesia. Trans. Br,

mycol, Soc. 41, 109-114.INGOLD, C. T. (1959). Aquatic spora of Omo forest, Nigeria. Trans. Br. mycol. Soc. 42,

479-485.INGOLD, C. T. (1961). Another aquatic spore-type with clamp connexions. Trans. Br,

mycol, Soc. 44, 27-30.LE'-JOHN, H. B. (1965). Sierra Leone freshwater hyphomycetes. Trans. Br. mycol. Soc.

48, 261-264.NILSSON, S. (1962). Some aquatic hyphomycetes from South America. Svensk bot. Tidskr,

56, 35 1-361.

(Accepted for publication I I September 1967)