Hydraena (Hydraenopsis) saotometerrestris, 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 : 594-595

Hydraena (Hydraenopsis) saotometerrestris sp. nov.

( Figs. 1A–B , 2A & C )

Type locality. São Tomé, Bom Sucesso, forest close to radio tower, ca. 1320 m.

Type material. Holotype (male): “ SÃO TOMÉ // Bom Sucesso // Aerial // 6–7.vi.1999 ” “Winkler// sample” “ A. Polazsek // BMNH ( E) 2005-138” (genitalia extracted and mounted on same card) and red holotype label ( NHML).

Paratypes (14): São Tomé: 3♁ 1♀, same data as holotype; 4♁ 6♀ “ SÃO TOMÉ, Pico de São Tomé// ref: ANHRT2018-216, leg. C.R.Turner // 00°16′11.5″N 6°32′38.8″E, 1936 m // 18 Jan 2018, hand searching wet dead leaves// on forest floor” All with red paratype labels ( AMG, CDTB, CCRT, NHML, NHMW).

Description. Size: Holotype: BL 1.50 mm; EL 0.95 mm; EW 0.70 mm. Paratypes: Males BL 1.50–1.55 mm; EL 0.95–1.00 mm; EW 0.65–0.70 mm. Females BL 1.65–1.70 mm; EL 1.00– 1.05 mm; EW 0.70–0.75 mm.

Colour: Dorsum dark reddish brown ( Fig. 1A ); margins of pronotum paler than disc; clypeus and labrum paler; legs reddish brown, tarsi paler; maxillary palpi yellowish brown; antennal stem segments pale yellowish brown, club somewhat darker; Venter reddish brown; pronotal hypomeron, elytral epipleurs and abdominal ventrites paler; cardo, stipes and palpifer yellow.

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 10 ommatidea in longest series. Labrum transverse, deeply emarginate anteromedially. Anterior and lateral margins broadly upturned, with short, curved setae. Upper surface of labrum shining, with fine microreticulation and scattered punctures bearing short, recumbent setae. Clypeus shining with sparse, fine 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 sharp and slightly obtuse; surface shining, with moderate, large, shallow punctures, bearing fine recumbent to decumbent setae; punctures in centre spaced 0.2–3 puncture diameters apart. Maxilary palpi with segment 3 and 4 somewhat expanded.

Pronotum: Transverse, strongly arched, slightly cordiform, broadest just behind middle. Sides dentate, with smaller, curved setae; broadly rounded at broadest point, then almost straight to hind angles and rounded to front angles. Hind angles rounded, square; front angles broadly rounded, slightly obtuse. Front margin broadly emarginate in middle half, then sinuous to front angles. Hind margin 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 very shallow, elongate, open laterally; posterolateral pronotal foveae very shallow, slightly elongate, open posteriorly.

Elytra: Broad, arched, moderately elongate, widest close to middle. Sides weakly rounded to shallowly emarginated apex. Elytral margin broadly 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 transverse, strongly acuminated apicomedially; anterior and lateral margins with dense, stout, erect to suberect, elongate setae; lateral angles broadly rounded; surface shining, with sparse, fine punctures bearing long, fine, recumbent to decumbent setae. Submentum shining, with shallow, sparse, fine punctures bearing fine recumbent to decumbent setae. Gena shining; anterior rides weak and arcuate. Prosternal intercoxal process narrow, shining, carinate; strong triangular posterior projection over mesoventrite. Pronotal hypomera very broad, weakly shining, without visible reticulation. Elytral epipleura very 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 strongly rugosely punctured with very long setose vestiture and elongate, triangular posteromedian depression, opening posteriorly. Metaventral plaques reduced to arcuate, shining areas adjacent to posteromedian depression with sparse vestiture. Abdominal intercoxal sclerite width at arcuate posterior margin approx. 3x that of apex of mesoventral intercoxal process. Abdominal ventrites 1–4 shining, with long setose vestiture. Ventrite 5 shining, vestiture restricted to basal 1/3; irregular row of fine punctures bearing elongate setae close to apical margin; apical margin broadly arcuate. Ventrite 6 somewhat shining, with strong transverse microreticulation, devoid of vestiture. Ventrite 7 with strong transverse microreticulation. Reflexed portion of tergite 9 with transverse microreticulation and short internal apodemes.

Aedeagus: Elongate ( Fig 1B ); main piece rather straight, flattened over apical 1/ 3 in lateral view, with complex apex; base of gonopore-bearing flagellum with short dorsal hood. Parameres very small, stout, attached approx. 1/3 from apex on main piece.

Females: Largely as males. Apical abdominal ventrites with more extensive vestiture.

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. For separation from H. turneri sp. nov. see under than species below.

Etymology. Named in reference to the geographical location and apparent ecology, in forest leaf litter.

Distribution and ecology. Known from two high-altitude forest locations in the centre of the island, at least one of which (Pico de S„o Tomé) is within Parque Natural Ôbo. Likely widespread in suitable habitat in these mountains.At the type locality, material was collected from leaf litter with a Winker sampler. Clive Turner collected most specimens by hand searching leaf litter below tree ferns just below the summit of Pico de S„o Tomé, beetles always being found crawling in water films on wet, well-decayed leaves. Sifting in the same place only produced one specimen.

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.