Xyrodromeus ambiguus, Gattolliat, Jean-Luc, 2004

Gattolliat, Jean-Luc, 2004, A distinctive new species of Xyrodromeus Lugo­Ortiz & McCafferty (Ephemeroptera: Baetidae) from Madagascar, Zootaxa 452, pp. 1-10 : 2-8

Xyrodromeus ambiguus sp. n.

Larva

Maximum length: Body 7.7 mm. Cerci 10.3 mm and terminal filament 3.2 mm.

Head. Brown with vermiform marks on vertex and frons poorly visible. Antennae pale cream yellow, except scape and pedicel brown. Turbinate eyes purple.

Labrum (Fig. 1) trapezoid, broader apically; distal margin with numerous simple setae; dorsal surface with an arc of about 20 long and thin setae, submedial pair of setae present, abundant short setae; ventral surface with a row of 3 minute setae and a row of very thin setae parallel to distal margin.

Hypopharynx as in figure 2 with minute thin setae, lingua not trilobate.

Right mandible (Fig. 3) with two sets of fused incisors, the inner one extremely reduced; prostheca reduced to a simple filament; a complete row of short setae between prostheca and mola; tuft of small setae near the mola; tuft of setae at the apex of the mola reduced to 3 setae; basal half with a stout seta perpendicular to the margin and abundant small setae dorsally.

Left mandible (Fig. 4) with completely fused incisors; prostheca with very reduced denticles and a comb­shape structure apically; abundant short setae between prostheca and mola; tuft of setae under the mola; tuft of setae at the apex of the mola reduced to 3 or 4 setae; basal half with a stout seta perpendicular to the margin and abundant small setae dorsally.

Maxillae (Fig. 5) with distal tooth opposed to the 3 others; 2 rows of setae, the first one formed by abundant small setae and the second by 2 long stout setae ending with 5 setae twice as long as the others; 6 setae at the base of the galea roughly arranged in a row; 1 single small seta perpendicular to the margin of the galea.

Labium (Fig. 6) with glossae slightly shorter than paraglossae; glossae with long setae, a few small setae on the dorsal margin; paraglossae apically with 3 rows of setae; first segment of the labial palp 0.9 x length of the second and third combined; second segment with a moderately rounded distomedial expansion, covered with numerous thin setae, row of about 10 thin setae; third segment cap­like, with small setae.

Thorax. Brown with attenuate darker flame­like marks.

Figs 1 to 6. Larval structures of Xyrodromeus ambiguus : 1: labrum (left: ventral; right: dorsal). 2: hypopharynx. 3: right mandible. 4: left mandible. 5: right maxilla. 6: labium.

Hind wing pads present.

Legs colouration: femora brown with yellow marks; tibiae yellow with inner margin darker; tarsi yellow apically brown.

Legs (Fig. 7). Ventral margin of coxae with small pointed setae.

Femora dorsally with a row of abundant long setae; submarginal row of numerous minute setae restricted to the proximal third; dorsoapical patch of several small blunt setae; numerous small setae on the ventral margin.

Tibiae with a row of minute blunt setae dorsally; apex with 1 medium seta dorsally; ventral margin with minute pointed setae; tibio­patellar suture absent.

Tarsi dorsally almost bare, ventrally with about 9 setae, apical ones longer; tarsal claws (Fig. 8) with two rows of 5 teeth increasing in length, subapical pair of setae present.

Second and third legs similar to foreleg, except tibio­patellar suture present.

Abdomen. Colouration of the terga brown, darker medially without pattern; terga 8–9 lighter.

Terga (Fig. 11) with scale bases, posterior margin with blunt spines.

Sterna yellow; with scale and setal bases, smooth posterior margin with a continuous row of setae without spines (Fig. 12).

Asymmetrical gills on abdominal segments 1 to 7; gill 1 (Fig. 9) reduced, without tracheation; gills 2–7 (Fig. 10) with dark tracheation, serrated with thin setae apically and posteriorly.

Paraproct (Fig. 13) expanded, surface with numerous scale and setal bases, about 10 well­developed pointed marginal spines and small spines; posterolateral extension with about 10 scale bases and with numerous small spines along the margin.

Male imago

Maximum length: Body 7 mm. Forewing 7.5 mm. Hindwing 1.2 mm.

Head. Light brown without marking. Turbinate eyes purple, darker at the base.

Thorax. Coppery brown. Forewing (Fig. 14) hyaline, with one intercalary vein between longitudinal veins; pterostigma with 5 to 7 cross­veins that do not reach the subcostal vein. Hindwing (Fig. 15) hyaline with 2 longitudinal veins, joined at the base; 2 distinct but not widely separated spurs on the costal margin.

Abdomen. Terga pale cream with a brown stripe near the distal margin; sterna pale cream.

Genitalia (Fig. 16) with 3­segmented gonopods, limit between the first and the second barely visible. Basal segment with a pointed apophysis at the apex of the inner margin; first segment stout, without setae; second segment with subparallel margins; third segment elongate, outer margin concave.

Figs 7 to 13. Larval structures of Xyrodromeus ambiguus : 7: foreleg. 8: tarsal claw. 9: first gill. 10: fourth gill. 11: posterior margin of the fourth tergum. 12: posterior margin of the fourth sternum. 13: paraproct.

Figs 14 to 16. Male imaginal structures of Xyrodromeus ambiguus : 14: forewing. 15: hind wing. 16: genitalia.

Etymology

This specific epithet is from the Latin, meaning ambiguous, because of the phylogenetic position of the species being intermediate between Xyrodromeus and Dicentroptilum .

Ecology

Xyrodromeus ambiguus was collected in small to medium streams (1.5 to 6 m wide, 0.2 to 0.6 m depth) with moderate to fast flow (0.5 to 1.3 m /s). All the localities are in tropical rain forest without human activity. This species has been found in a restricted number of localities, but when it is present, it is one of the dominant species. Xyrodromeus ambiguus co­occurs with the four other Malagasy species (with the four species in the Marojejy area, and with X. namarona and X. sartorii in La Montagne d'Ambre National Park for example).

Material examined

Holotype

1 male larva, (P0818), Madagascar, Antongombato bas., Makis riv., Loc. Roussette Station (Montagne d'Ambre National Park), Long. 49°10'09" E, Lat. 12°31'40" S, Alt. 1075 m, 23.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

Paratypes

168 larvae (3 larvae on slide 818d, 818e, 818f), same data as holotype

8 larvae, (P0189), same locality as holotype, 27.03.1994. Elouard, J.­M. & Sartori, M.

14 larvae, (P0191), same locality as holotype, 28.03.1994. Elouard, J.­M. & Sartori, M.

1 male imago from rearing (on slide), (P0194), same locality as holotype, 29.03.1994. Elouard, J.­M. & Sartori, M.

12 larvae, (P0200), same locality as holotype, 0 2.04.1994. Elouard, J.­M. & Sartori, M.

3 larvae, (P0364), same locality as holotype, 31.03.1995. Ralaiteferana, A. & Blanc, L.

2 larvae, (P0371), same locality as holotype, 0 3.04.1995. Blanc, L. & Ralaiteferana, A.

3 larvae, (P0752), same locality as holotype, 17.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

11 larvae, (P0806), same locality as holotype, 20.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

59 larvae (1 female larva on slide 826c), (P0826), same locality as holotype, 25.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

2 larvae (one male larva on slide 193b), (P0193), Madagascar, Antongombato bas., Makis riv., Loc. Roussette Station (Montagne d'Ambre National Park), Long. 49°10'21" E, Lat. 12°31'38" S, Alt. 1050 m, 29.03.1994. Elouard, J.­M. & Sartori, M.

1 larva, (P0196), same locality as P0193, 30.03.1994. Elouard, J.­M. & Sartori, M.

40 larvae (P0828), same locality as P0193, 25.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

9 larvae, (P0814), Madagascar, Antongombato bas., Makis riv., Loc. 100m down the Great Waterfall (Montagne d'Ambre National Park), Long. 49°10'14" E, Lat. 12°29'17" S, Alt. 675 m, 22.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

58 larvae, (P0822), same locality as P0814, 24.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

41 larvae (P0819), Madagascar, Antongombato bas., Makis riv., Loc. Roussette Station (Montagne d'Ambre National Park), Long. 49°10'21" E, Lat. 12°31'27" S, Alt. 1030 m, 23.03.1999. Gattolliat, J.­L. & Rabeantoandro, Z.

Other material

3 larvae, (P0510), Madagascar, Mangoro bas., Manambolo riv., Loc. Mandraka, Long. 47°55'58" E, Lat. 18°55'17" S, Alt. 1050 m, 18.10.1995. Pilaka, T.

1 larva, (P0606), Madagascar, Lokoho bas., Manantenina riv., Loc. Marojejy Camp I, Long. 49°46'20" E, Lat. 14°26'02" S, Alt. 450 m, 0 4.10.1996. Legrand, J. & Randriamasimanana, D.

1 male and 1 female subimagos (form rearing), 2 larva, (P0613), Madagascar, Lokoho bas., Manantenina riv., Loc. Marojejy Camp I, Long. 49°46'07" E, Lat. 14°26'03" S, Alt. 480 m, 10.10.1996. Legrand, J. & Randriamasimanana, D.

4 larvae, (P0620), Madagascar, Lokoho bas., unnamed river, Loc. Marojejy Camp II, Long. 49°45'37" E, Lat. 14°26'10" S, Alt. 750 m, 14.10.1996. Legrand, J. & Randriamasimanana, D.

3 larvae, (P0621), Madagascar, Lokoho bas., unnamed river, Loc. Marojejy Camp II, Long. 49°45'33" E, Lat. 14°26'05" S, Alt. 750 m, 15.10.1996. Legrand, J. & Randriamasimanana, D.

7 larvae, (P0623), Madagascar, Lokoho bas., Manantenina riv., Loc. Marojejy Camp II, Long. 49°45'37" E, Lat. 14°25'57" S, Alt. 720 m, 17.10.1996. Legrand, J. & Randriamasimanana, D.

79 larvae, (P0872), Madagascar, Betaolana bas., Ambolokopatrika riv., Loc. Betaolana Camp 1, Long. 49°26'47" E, Lat. 14°32'25" S, Alt. 800 m, 0 8.10.1999. Doumenq, E.

66 larvae, (P0874), same locality as P0872, 0 9.10.1999. Doumenq, E.

12 larvae, (P0875), same locality as P0872, 10.10.1999. Doumenq, E.

8 larvae, (P0893), Madagascar, Ampary bas., Anlanbe riv., Loc. Anjanaharibe Sud­ Ouest Camp1, Long. 49°26'53" E, Lat. 14°47'00" S, Alt. 1200 m, 26.10.1999. Doumenq, E.

18 larvae, (P0897), same locality as P0893, 27.10.1999. Doumenq, E.

35 larvae, (P0898), same locality as P0893, 30.10.1999. Doumenq, E.

6 larvae, (P0899), same locality as P0893, 31.10.1999. Doumenq, E.

112 larvae (3 larvae on slide 1009a, 1009c and 1009d), (P1009), Madagascar, Lokoho bas., Manantenina riv., Loc. Marojejy Camp2, Long. 49°45'58" E, Lat. 14°26'23" S, Alt. 800 m, 26.11.1999. Doumenq, E.