L'adulte et la larve d'un nouveau genre d'éphémère (#Baetidae$) sont décrits.Ce genre est un groupe-frère de l'éphémère sud-africaine, #Demoulinia$. Deux espèces sont connues, provenant toutes deux de Guinée. Elles se rencontrent dans les zones de courant calme, près des rives des ruisseaux forestiers. (Résumé d'auteur

Gillies, M.T.

Wuillot, J.

Horizon / Pleins textes

Cheleocloeon, a new genus of Baetidae 
(Ephemeroptera) from West Africh 
Jean WUILLOT (1) and M. T. GILL~ES (2) 
ABSTRACT 
A description is given of the adult and nymph of Cheleocloeon a new qenus of mayflies (Baetidae) from Guinea. 
The genus is regarded as a sister group of the South Af rican mayfly, Demoulinia. Two species are known, bath of 
them found in the slack rvater on the edge of forested sfreams. 
KEYWORDS : Mayflies - Descript.ions - New species - Adults - Nymphs - Taxonomy. 
RÉSUMJ? 
CHELEOCLOEON, UN GENRE NOUVEAU DE BAETIDAE (EPH.) POUR L’AFRIQUE DE L’OUEST 
L’adulte ei la larve d’un nouveau genre d’éphémère (Baetidae) sont décrits. Ce genre est un groupe-frère de 
l’éphémère sud-africaine, Demoulinia. Deux espèces sont connues, provenant toutes deuz de Guinée. Elles se ren- 
contrent dans les zones de courant calme, près des rives des ruisseaux forestiers. 
MOTS CLÉS : fiphémères - Description - Taxonomie - Espèce nouvelle - Adulte - Larve. 
INTRODUCTION 
In discussing the origins of the Afrotropiçal Baeti- 
dae, GILL~ES (1990) pointed out that the fauna was 
dominated by genera with, in the adult, single mar- 
gina intercalaries in the fore wing and, in t,he 
nymph, a tuft of setae on the right mandible at. the 
base of the prost.heca. Yet another new genus of this 
group has recently corne to light in the course of a 
study of the baetid fauna of rivers in the forest belt. 
in Guinea. The adults of two closely related species 
were obtained by rearing. Unlike the adults, the 
nymphs are highly distinc.t.ive. They are described 
here as members of the new genus Cheleocloeon. 
Types of the new species are deposited in the 
Muséum national d’histoire naturelle de Paris. 
DESCRIPTION 
Cheleocloeon gen. nov. 
Adult : Small species. Fore wing with single margi- 
nal intercalaries; hind wing absent. $ forceps with 
3 segments, t.erminal segment elongat,ed. 
Nymph : Bath mandibles with setal tuft at base of 
prosthecae. Labial palp with apical media1 process of 
second segment unusually and strongly produced 
and point,ed; base of glossa not expanded at base, 
(1) Orsfom, Muséum national d’hisfoire naturelle, 43 rue Cuvier, 7.5231 Paris, France. 
(2) Whitfeld, Hamsey, Leuves, Sussex BN8 5TD, England. 
Rev. Eiydrohiol. trop. 26 (3) : 21.3-217 (1993). 
214 J. WUILLOT, IN. T. GILLIES 
about equal in width t,o paraglossa. Maxillary palp 
wit.h 2 segments, long, extending well beyond galea 
lacinia. Legs fine, tarsal claws long wit,h minut,e 
teeth at. base. Gills present on 7 segments, lamella 1 
paddle-shaped, longer than a11 other gills. Cerci and 
terminal filament about equal in length. 
Type species : C. yolandae Wuillot. 
Etymology : From chele, latin, the claw of a scor- 
pion or similar animal, in reference to the pinc.her- 
like appearance of the labial palps. 
Cheleocloeon yolandae sp. nov., Wuillot 
$ image : Turbinate eyes pale brown. Legs cream, 
fore leg with tibia 1.5-1.75 times as long as femur, 
fore tarsus as long as or longer than tibia. Fore wing 
hyaline (fig. l), some specimens with a milky wash in 
the distal part of costal and subcostal areas; stigma 
with 3-7 crossveins. Hind wing absent,. Abdominal 
terga uniformly brown to fawn, without characteris- 
tic markings. Forceps with 3 segments (fig. 2), the 
basa1 segment &out and partially fused with second 
segment, apical segment elongate. 
3 wing 3-4 mm; body (without cerci) 3-4 mm. 
FIG. 1-2. - Cheleocloeon yolandae sp. nov. 3 imago. 
1 : fore wing. 2 : forceps. 
Cheleocloeon yolandae sp. nov. 8 imago. 1 : aile 1. 2 : genitalia. 
Nymph : Mouthparts (figs. 3-7) : dorsal surfac,e of 
labrum with a line of short hairs interna1 t,o antero- 
lateral margin; canines of right mandible partially 
fused, prostheca with 3-4 subequal teeth at apex; oh 
left., canines fused, prostheca scraper-like, with 
about 6 terminal teeth; apical media1 process of 
second segment of labial palp marked off from the 
rest. of the segment by a linear thickening of the inte- 
gument. Margins of femora sparsely ornamented 
with spine-like setae (fig. 8). In mature nymph the 
main veins in the wing-bud are c.onspicuously pig- 
ment,ed. Abdominal terga extensively marked, the 
pigment most heavily developed on 1, III, VI and 
IX (fig. 10). Gill lamellae on segment.s II-VII sube- 
qual, ovate ; lamella 1 1.5 times as long as rest. of 
gills, broadly paddle-shaped in distal half (fig. 9). 
Terminal filament subequal t.o cerci, feathered to 
apex. 
Maferial : Guinea : holotype 6 image with associa- 
ted nymph skin on slide, R. Niandam, Sassambaya, 
02.89; paratypes, same provenance, 3 $3, 02.88, 
02.92, 21 nymphs 03.88, 02.92; 1 9 subimago with 
nymph skin fragments on slide, R. Diani, near 
Nzebela, 31.01.88 ; 4 nymphs, same provenance. 
Mali : R. Bakoye, Kokofata, 01.92. 
Cheleocloeon carinatum sp. noy., Wuillot 
$ imago : Turbinate eyes cream. Legs cream, fore 
tibia 1.5-1.75 times as long as femur. Fore wing hya- 
line (fig. Il), marginal intercalaries incomplet,e in 
basa1 interspaces; stigma with 2 crossveins. Hind- 
wing absent. Abdominal terga uniformly brown t.o 
fawn, without charact.eristic markings. 8 forceps 
(not figured) with 3 segments, the distal segment 
elongated. 
$ wing, 3-4 mm; body 3-4 mm. 
Nymph : Mouthparts (figs. 12-16) : Labrum dor- 
sally with marginal setae only ; canines of both man- 
dibles fused, right prostheca with a single t.ooth 
below sharply pointed apex, setal tuft at base of 
prosthecae present on bot,h sides; maxillary palp 
with 2 segments, muc.h longer than galea-lacinia ; 
apical media1 process of labial palp strongly produ- 
ced and drawn out to a fine point. Legs fine (fig. 17), 
tarsal claws minut,ely toothed towards base. Gill 
lamellae (fig. 18) present on segments I-VII, that on 
1 slightly longer than the rest, paddle-shaped in the 
outer one-third. Abdominal terga with blunt, median 
spurs on segments 1 to VI or VII (fig. 20); markings 
(fig. 19) maximal on t,erga III, VI and IX. Terminal 
filament subequal to cerci, feathered. 
Material : Guinea : $ imago (damaged), R. Nian- 
dam, Sassambaya, 02.89; holotype nymph, same 
provenance, 03.88; 1 nymph, 02.87, 2 nymphs, 
03.88, same provenance. 
Reu. Hydrobiol. frop. 26 (3) : 213-217 (1%‘3). 
FIG. 3-7. - Cheleocloeon yolandae sp. nov. 
nymph, mouthparts. 3 : labrum (dorsal view on 
left, ventral on right). 4 : distal margin of right 
mandible. 5 : distal margin of left mandible. 
6 : labium. 7 : maxilla. 
Cheleocloeon yolandae sp. nov. nymphe, pièces 
buccales. 3 : labrum (vue dorsale à gauche, vue 
ventrale à droite). 4 : marge disfale de la mandibule 
droite. 5 : marge distale de la mandibule gauche. 
6 : labium. 7 : maxille. 
FIG. S-10. - Cheleocloeon yolandae sp. nov. nymph. 8 : fore leg 
(wit.h det.ail of leg). 9 : gill lamellae I-VII (wit.h detail of distal 
ant.erior margin of gill IV). 10 : abdomen, dorsal view. 
Cheleocloeon yolandae sp. nov. nymphe. 8 : patte J (avec détail 
de la patte). 9 : trachéobranchies I-VII (avec délai1 de la marge 
antérieure de la trachéobranchie IV). 10 : abdomen, vue dorsale. 
FIG. 11. - Cheleocloeon carinafum sp. nov. 6 imago. 
Il : fore wing. 
Cheleocloeon rarinaturn sp. nou. $ imago. 11 : aile I. 
FIG. 17-20. - Cheleocloeon carinatum sp. nov. nymph. 
17 : fore leg (with detail of claw). 18 : Gill lamellae 1, II, IV-VII, 
(with detail of distal anterior margin of gill V). 19 : abdomen, 
dorsal view. 20 : abdomen in lateral view (pigmentation not 
represented). 
Cheleocloeon carinatum sp. nov. nymphe. 17 : paffe 1. 
18 : trachéobranchies I, II, IV-VII, (avec défail de la marge 
distaleantérieure de la branchie V). 19 : abdomen, vue dorsale. 
20 : vue latérale d’abdomen (la pigmentation n’est pas représenfée). 
FIG. IP-16. - Chelroefoeon carinatum sp. nov. nymph, mrn1thpart.s. 12 : labrum (dorsal view on left-, ventral on right.). 13 : distal 
margin of right. mandible. 14 : distal margin of left mandible. 15 : labium. 16 : maxilla. 
Cheleoclooon carinat.um sp. nov. nymphe, pièces buccales. 12 : labrum (vue dorsale à gauche, vue ventrale h droite). 13 : marge distale de 
mandibule droite. 14 : marge distale de mandibule gauche. 15 : labiam. 16 : maxille. 
Rra. Hydrohid. frop. 26 (3) : X3-217 (199.3). 
A NEW GENUS OF BAETIDAE FROM WEST AFRICA 217 
AFFINITIES 
The adult of C. carinafum differs from that of 
C. yolandae in the absence of marginal intercalaries 
in the basa1 interspaces of the fore wing. The nymph 
differs by the presence of median, tergal spurs on the 
abdomen, the t,ergal markings and the shorter 
lamella of gill 1. 
A highly characteristic feature of C/leleocloeon is 
the exceptional length of t.he first gill lamella. In 
practically a11 known genera of Baetidae t,his lamella 
is either subequal to those of the ot.her gills, much 
smaller or sometimes absent altogether. In C. yolan- 
due not only is it the longest of the gills but. broadens 
out into a paddle-shaped organ in the dist.al half. In 
t:his it differs from C. carinafum, in which the elonga- 
tion is less and the lamella lacks the distal broade- 
ning. The two species also differ in the tergal pattern 
and the absence in C. yolandae of the median tergal 
spurs characteristic of C. carinafum. 
In living nymphs, while at rest, the first gill is held 
above the body like a banner and act.ively vibrated. 
In contrast, the remaining gills are held passively, 
close to the abdomen. 
DISCUSSION 
Cheleocloeon would seem to be a sister group of t.he 
South African mayfly Demoulinia crassi (Demoulin). 
It shares with this genus loss of the hind wing in the 
adult and the long, fine tarsal claws with minute 
denticles. Cheleocloeon has the ant,ero-media1 process 
of the second segment of the labial palp drawn out to 
a point.. We have re-examined specimens of Demouli- 
nia and find that this process is drawn out, into a fine 
recurved point. This apotypic character is not 
apparent in the original figure of GRASS (1947), and 
the palp is redrawn here (fig. 21). On the other hand, 
the forceps of the $ are most, unusual, the apical 
segment arising from the inner aspect of the apex of 
the 2nd segment,. In Cheleocloeon the forceps are nor- 
mal for the group. The canines of the mandibles in 
21 
FIG. 21. - Dernoulinia crassi (Demoulin). 21 : labial palp. 
Demoulinia crassi (Demoulin). 21 : palpe labiale. 
Demouiinia are divided, while those of Cheleocloeon, 
being fused on bath sides, presumably represent the 
more derived character stat.e. 
A number of baet,id mayflies have become adapted 
to the slowmoving wat,er on the margins of rivers, for 
example Pofamocloeon Gillies and the two genera dis- 
cussed here. They are characterised by long fine 
claws, apparently as an adapt.ation t,o silted subs- 
trates. Similar claws are seen in the North American 
mayfly, Apobaefis Day, a species known to frequent 
artificial irrigation channels, EDMUNDS et a/. (1976). 
Since this genus is not at a11 closely related t,o these 
African forms, it is evident. that, what. we see is yet 
anot,her example of parallel evolution in the Baet,idae. 
ACKNOWLEDGEMENTS 
We are indebted t.o Dr. J.-M. Elouard for providing facili- 
tics for us t.o work in Guinea. We would like to thank 
Mr. M. Traoré for technical assistance. 
Manuscrif accepté pur le Con&! de rédaction le 26 décembre 1993 
REFERENCES 
CRASS (R. S.), 1947. - The May-flies (Ephemeroptera) of Natal 
and the Eastern Cape. Ann& Natal Museum, 11 : 37-110. 
EDMUNDS (G. F.), Jr., JENSEN (S. L.), BERNER (L.), 1976. - 
The Maytlies of Norfh and Central America. Minneapolis, 
University of Minnesota Press, 330 p. 
GILL~ES (M. T.), 1990. - A revision of the African species of 
Centropfilczm Eaton (Baetidae, Ephemeroptera). Aquafic 
Insecfs, 12 : 97-128. 
R~U. Hydrobiol. trop. 26 (3) : 213-217 (1993). 


Cheleocloeon, a new genus of Baetidae (Ephemeroptera) from West Africa

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