Hydraena (Hydraenopsis) turneri, Bilton, 2023

Bilton, David T., 2023, Two new species of Hydraena Kugelann, 1794 from São Tomé Island-an apparent adaptive radiation (Coleoptera, Hydraenidae), Zootaxa 5254 (4), pp. 593-600 : 595-599

Hydraena (Hydraenopsis) turneri sp. nov.

( Figs. 1C–D , 2B–C )

Type locality. São Tomé, trail from Ponta Figo , seepage, 0˚17′10′′N 6˚34′8.6′′E, 629 m.

Type material. Holotype (male): “ SÃO TOMÉ, Ponta Figo trail// ref: ST27, leg. C.R.Turner // 00°17′10.3”N 6°34′8.6”E, 629 m // 28 October 2016, seep on cutting by track// steep mountain slope, primary forest” (genitalia extracted and mounted on same card) and red holotype label ( NHML).

Paratypes (58): São Tomé: 35♁ 23♀, same data as holotype. All with red paratype labels ( AMG, CDTB, CCRT, ISAM, NHML, NHMW).

Description. Size: Holotype: BL 1.55 mm; EL 0.95 mm; EW 0.65 mm. Paratypes: Males BL 1.45–1.55 mm; EL 0.85–0.90 mm; EW 0.60–0.65 mm. Females BL 1.60–1.65 mm; EL 0.95–1.00 mm; EW 0.65–0.70 mm.

Colour: Dorsum dark brown to black ( Fig. 1C ); anterior angles of pronotum and elytral margins paler; legs brown, tarsi slightly paler; maxillary palpi light brown; antennal stem segments brown, club somewhat darker; Venter dark brown to black; underside of head, pronotal hypomeron and elytral epipleurs paler brown.

Head: Broadly triangular, broadest at hind margin of eyes; narrowing abruptly in front of clypeus; narrowest at apex of labrum. Compound eyes moderate, occupying approximately 1/2 of side margin of head excluding labrum, with 12 ommatidea in longest series. Labrum transverse, deeply emarginate anteromedially. Anterior and lateral margins upturned, with short, flat setae. Upper surface of labrum shining, with fine microreticulation and scattered punctures bearing short, recumbent setae. Clypeus shining with moderate, medium punctures bearing short, decumbent setae; with weakly arcuate anterior margin, anterolateral angles obtuse. Frontoclypeal suture distinct, broadly arcuate. Frons much wider than clypeus, with front angles rounded and slightly obtuse; surface shining, with moderate, large, shallow punctures, bearing fine recumbent to decumbent setae; punctures in centre spaced 0.1–4 puncture diameters apart. Maxilary palpi with segment 3 and 4 somewhat expanded.

Pronotum: Transverse, weakly arched, slightly cordiform, broadest at middle. Sides dentate, with smaller, curved setae; slightly narrowing from widest point to front angles; abruptly narrowing and weakly arcuate to hind angles. Hind angles slightly acuminate and obtuse; front angles broadly rounded, obtuse. Front margin broadly emarginate in middle half, then sinuous to front angles. Hind margin almost straight, very weakly bisinuate around centre. Disc shining, devoid of microreticulation; moderate, large, shallow punctures, as on head, bearing fine recumbent to decumbent setae; punctures in centre spaced 0.5–3 puncture diameters apart. Anterolateral pronotal foveae shallow, open laterally; posterolateral pronotal foveae very shallow, slightly elongate, open posteriorly.

Elytra: Arched, moderately elongate, widest close to middle. Sides weakly rounded to shallowly emarginated apex. Elytral margin explanate, from just behind shoulder to close to apex; minutely serrate. Elytra shining, with 15 non-striate rows of medium, shallow punctures, bearing fine recumbent setae, most not reaching anterior margin of next puncture in series; punctures slightly larger than on pronotum. Elytral disc flat, gradually declining to apex over posterior half.

Wings: Full.

Venter: Mentum slightly elongate, sharply acuminated apicomedially; anterior and lateral margins with dense, stout, erect, pointed setae; lateral angles rounded; surface shining, with sparse, fine punctures bearing short peglike setae in centre; setae longer and recumbent to decumbent close to posterior margin. Submentum shining, with transverse ridges and shallow, fine punctures bearing fine recumbent to decumbent setae. Gena shining; anterior rides weak and arcuate. Prosternal intercoxal process narrow, shining, carinate; weak triangular posterior projection over mesoventrite. Pronotal hypomera broad, weakly shining, without visible reticulation. Elytral epipleura broad, shining; continued to approx. 1/6 from apex. Mesoventrite shining, rugosely punctate, with sparse, long setose vestiture; plaques strongly developed, median, admedian and adlateral; mesoventral intercoxal process with margins slightly concave around centre, shining and rugose, lateral margins slightly raised. Metaventrite shining, shallowly, rugosely punctured with long setose vestiture and elongate posteromedian depression, opening posteriorly. Metaventral plaques narrow, linear, shining areas adjacent to posteromedian depression with sparse vestiture. Abdominal intercoxal sclerite width at arcuate posterior margin approx. 2x that of apex of mesoventral intercoxal process. Abdominal ventrites 1–4 shining, with long setose vestiture. Ventrite 5 shining, devoid of vestiture, with irregular, transverse setal row anteriorly and posteriorly; apical margin weakly arcuate. Ventrite 6 shining, with weak transverse microreticulation and irregular, transverse setal row posteriorly. Ventrite 7 with weak transverse microreticulation. Reflexed portion of tergite 9 with transverse microreticulation and short internal apodemes.

Aedeagus: Elongate ( Fig 1D ); main piece rather straight, with dorsally reflexed apex in lateral view; gonoporebearing flagellum attaching below well-developed dorsal hood, with crenulated margin. Parameres very small, stout, attached approx. 1/3 from apex on main piece.

Females: Largely as males.

Differential diagnosis. Amongst known Afrotropical Hydraena the new species is best distinguished by the form of the aedeagus, with small, distally positioned parameres, and a short, curved gonopore-bearing flagellum with a dorsal hood. It differs from H. soatometerrestris sp. nov. on a number of external and aedeagal characters, particularly: darker dorsal colouration; pronotum less constricted towards front angles; elytra narrower, somewhat more parallel-sided in middle, with narrower explanate margin; metaventrite sculpture less marked and less obviously rugose, posteromedian metaventral depression more elongate, metaventral plaques narrower and more elongate; ventral vestiture shorter and denser; aedeagus smaller, with more strongly pronounced angle on right-hand side in ventral view and more well-developed hood over base of gonopore-bearing flagellum (compare Figs 1B & D ).

Etymology. Named for my long-time friend Clive R. Turner, who collected all known material of this species, and a significant proportion of the type series of H. saotometerrestris sp. nov.

Distribution and ecology. Known only from the type locality, a seepage over rock and clay in primary forest beside a trail. Specimens were hand-picked from the surface of wet substrate, and were entirely submerged, suggesting an aquatic lifestyle. The wet substrate displayed two main forms of algal growth both covered by a thin layer of water, one a grey algal film which did not possess any Hydraena and a brown algal film on which they were all found and were well camouflaged on. Searches of other seeps, still waters & larger, flowing streams and rivers on the island by Clive Turner failed to locate any more Hydraena .

Figures

FIGURE 1. S„o Tomé Hydraena habitus and aedeagi (ventral and lateral views). A–B) Hydraena saotometerrestris sp. nov.; C–D) Hydraena turneri sp. nov. Scale bars A & C) = 1.0 mm; B & D) = 100 μm.

FIGURE 2. S„o Tomé Hydraena habitats and distribution. A) Hydraena saotometerrestris sp. nov., below Pico de S„o Tomé, 1936 m, leaf litter sifting (photo Clive Turner); B) Hydraena turneri sp. nov., seepage in primary forest beside track from Ponta Figo, 629 m (photo Clive Turner); C) known distribution on S„o Tomé, red circles Hydraena saotometerrestris sp. nov., yellow circle Hydraena turneri sp. nov., black outlines indicate type localities.