Afroptilum bicorne (Ulmer, 1909)

Kaltenbach, Thomas, Mary, Nathalie & Gattolliat, Jean-Luc, 2021, The Baetidae (Ephemeroptera) of the Comoros and Mayotte, African Invertebrates 62 (2), pp. 427-463 : 427

1. Afroptilum bicorne (Ulmer, 1909)

Figures 2a , 3 , 4 , 5

Diagnosis.

Nymph. Following combination of characters: A) labrum on dorsal surface with a simple submedian seta, a submarginal arc of ca. six simple setae and one simple seta in between; B) both mandibles with stout setae between prostheca and mola; C) labial palp segment II with a poorly developed distomedial protuberance; segment III conical and slightly pointed, with a minute, pointed projection at inner basal margin; D) maxillary palp approximately as long as galea-lacinia; E) fore femur rather broad, length ca. 3 × maximum width; dorsal margin with ca. 30 curved, spine-like setae; F) hind protoptera present; G) six pairs of gills.

Description.

Nymph (Figs 2a , 3 , 4 ). Body length 3.0-5.2 mm. Cerci: ca. 0.8 × body length. Paracercus: ca. 2/3 of cerci length. Antenna: approx. 2 × as long as head length.

Colouration (Fig. 2a ). Head, thorax and abdomen dorsally brown, abdominal segments II-VI medially with darker areas; head, thorax and abdomen ventrally light brown. Legs light brown, caudalii light brown.

Labrum (Fig. 3a ). Subrectangular, length 0.7 × maximum width. Distal margin with medial emargination and small process. Dorsally with long, fine, simple setae scattered over surface; a long, simple submedian seta, a submarginal arc of ca. six simple setae, decreasing in length laterally, and a medium, simple seta in between. Ventrally with marginal row of setae composed of lateral and anterolateral long, feathered setae and medial long, bifid setae; ventral surface with ca. six short, spine-like setae near lateral and anterolateral margin.

Right mandible (Fig. 3b, c ). Incisor and kinetodontium partly fused. Incisor with five denticles; kinetodontium with three denticles. Prostheca stick-like, distolaterally laterally denticulate. Margin between prostheca and mola with many long, stout setae. Tuft of setae at apex of mola present.

Left mandible (Fig. 3d-f ). Incisor and kinetodontium fused. Incisor with four denticles; kinetodontium with three denticles. Prostheca robust, apically with small denticles and comb-shaped structure. Margin between prostheca and mola straight, with medium simple setae, and minute denticles towards subtriangular process. Subtriangular process long and slender, above level of area between prostheca and mola. Comb-shaped structure below subtriangular process. Tuft of setae at apex of mola present.

Both mandibles with lateral margins almost straight. Basal half with fine, simple setae scattered over dorsal surface.

Hypopharynx and superlinguae (Fig. 3g ). Lingua approximately as long as superlinguae. Lingua longer than broad; medial tuft of stout setae well developed; distal half laterally not expanded. Superlinguae distally rounded; lateral margins rounded; fine, long, simple setae along distal margin.

Maxilla (Fig. 3h ). Galea-lacinia ventrally with two simple, apical setae under canines. Inner dorsal row of setae with three denti-setae, distal denti-seta tooth-like, slightly directed against canines, middle and proximal denti-setae slender and pectinate. Medially with one spine-like seta and five or six simple setae, increasing in length distally. Maxillary palp approximately as long as length of galea-lacinia; 2-segmented; palp segment II 1.4 × length of segment I; setae on maxillary palp fine, simple, scattered over surface of segments I and II; apex of last segment rounded.

Labium (Fig. 3i, j ). Glossa basally broad, narrowing toward apex; slightly shorter than paraglossa; inner margin with eight spine-like setae; apex with one long and one medium, robust, pectinate setae; outer margin with five spine-like setae; ventral surface with fine, simple, scattered setae. Paraglossa sub-rectangular, curved inward; apex rounded; with three rows of long, robust setae in apical area, a row of long, robust setae on distolateral margin, and one short, simple seta in anteromedial area; dorsally with two long, spine-like, simple setae near inner margin. Labial palp with segment I 1.1 × length of segments II and III combined. Segment I ventrally with short, fine, simple setae. Segment II with very slight distomedial protuberance; ventral surface with short, fine, simple setae; dorsally with 5-7 spine-like setae near outer margin. Segment III conical, apex slightly pointed; with a minute, pointed projection at inner basal margin; length 0.6 × width; ventrally covered with short, spine-like, simple setae and short, fine, simple setae.

Hind protoptera (Fig. 4f ) well developed.

Foreleg (Fig. 4a, b ). Ratio of foreleg segments 1.3:1.0:0.7:0.2. Femur. Length ca. 3 × maximum width. Dorsal margin with 30 curved, spine-like setae. Apex rounded, with pair of spine-like setae. A few lanceolate setae scattered on distomedial surface. Short, stout, lanceolate setae scattered along ventral margin; femoral patch absent. Tibia. Dorsal margin with row of scarce, fine simple setae; on apex one stout, apically rounded seta. Ventral margin with row of short, curved, spine-like setae, on apex a few longer setae. Anterior surface scattered with short, stout, lanceolate setae. Patellotibial suture absent. Tarsus. Dorsal margin bare. Ventral margin with row of curved, spine-like setae. Claw with one row of six denticles and a second row of three denticles; distally pointed; with three or four stripes; one pair of long, subapical setae.

Middle and hind legs. As foreleg, but with patellotibial suture.

Terga (Fig. 4c ). Surface with irregular rows of U-shaped scale bases. Posterior margin of tergum IV with triangular spines, approximately as long as wide.

Gills (Fig. 4d ). Present on segments II-VII. Margin with small denticles intercalating short, fine, simple setae. Tracheae extending from main trunk to inner and outer margins. Gill IV as long as length of segments V and VI combined; gill VII as long as length of segments VIII and IX combined.

Paraproct (Fig. 4e ). Distally not expanded, with 25-35 marginal spines. Surface scattered with U-shaped scale bases and micropores. Cercotractor with small, marginal spines.

Description.

Imago. See Ulmer 1909: p. 366, figs 1-3 and discussion below.

Distribution

(Fig. 5 ). Comoros (Anjouan, Mohéli), Mayotte.

Biological aspects.

In Mayotte, the specimens were collected at altitudes between sea level and 100 m, mostly together with one or several other species ( C. smaeleni , D. mayottensis sp. nov., L. glaucus ); in the Comoros, the specimens were collected at an altitude of 750 m, together with P. freitagae and P. cylindroculum . The characteristics and environmental conditions of the sampling site in the Comoros (Anjouan, Riv. Santsa) are described in Starmühlner (1979: p.651): river width 0.5-1 m, depth 2-10 cm, current 0.5- >1 m/s, water temperature ca. 24 °C, bottom substrata consisted of basaltic rock, boulders, gravel and sand at the borders.

Material examined.

Comoros • 9 nymphs; Anjouan, Riv. Santsa , upper course, near Adda-Douéni; 750 m; 21.03.1974; leg. F. Starmühlner; 2 on slides; GBIFCH00592757 , GBIFCH00592713 ; 7 in alcohol; GBIFCH00515654 , GBIFCH00515708 ; MZL, FAMU . Mayotte • 1 nymph; Koualé, Affl. foret 3 ; 12°47'43"S, 45°09'59"E; 18.05.2006; leg. N. Mary; on slide; GBIFCH00592758 ; MZL • 78 nymphs; Bas. Riv. Djalimou, Djalimou aval; 12°57'14"S, 45°06'51"E; 15 m; 14.04.2009; leg. N. Mary; 2 on slides; GBIFCH00592714 , GBIFCH00592722 ; 76 in alcohol; GBIFCH00515671 , GBIFCH00515709 ; MZL, FAMU • 4 nymphs; Bas. M’Tsangachéhi, Loc. M'Tsangachehi aval ; 12°53'04"S, 45°07'55"E; 10 m; 14.04.2009; leg. N. Mary; in alcohol; GBIFCH00515674 ; MZL • 1 nymph; Bas. Riv. Bouyouni, Loc. Bouyouni intermediaire ; 12°44'55"S, 45°08'36"E; 40 m; 16.04.2009; leg. N. Mary; in alcohol; GBIFCH00515675 ; MZL • 15 nymphs; Riv. Dembéni, Loc. Dembeni intermediaire ; 12°51'07"S, 45°09'41"E; 95 m; 20.04.2009; leg. N. Mary; 1 on slide; GBIFCH00592723 ; 14 in alcohol; GBIFCH00515718 ; MZL .

Figures

Figure 2. Nymphs, habitus: a Afroptilum bicorne b Dabulamanzia mayottensis sp. nov.

Figure 3. Afroptilum bicorne, nymph morphology: a labrum b right mandible c right prostheca d left mandible e left prostheca f comb-shaped structure below subtriangular process g hypopharynx and superlinguae h maxilla i labium j apex of paraglossa. Scale bar: 0.1 mm.

Figure 4. Afroptilum bicorne, nymph morphology: a foreleg b fore claw c tergum IV d gill IV e paraproct f metanotum (left side), with hind protopteron (mature nymph). Scale bars: 0.1 mm.

Figure 5. Distribution of Afroptilum bicorne and Cloeon smaeleni in the Comoros Archipelago.