Hydraena (Hydraenopsis) bubi, Hernando, Carles & Ribera, Ignacio, 2017

Hernando, Carles & Ribera, Ignacio, 2017, Two new terrestrial species of Hydraena Kugelann from the island of Bioko, Gulf of Guinea (Coleoptera: Hydraenidae), Zootaxa 4238 (2), pp. 281-286 : 281-283

Hydraena (Hydraenopsis) bubi sp.n. ( Figs 1 , 3–4 )

Type locality. Forest in Pico Biao, Province of Bioko Sur, island of Bioko, Equatorial Guinea. Type material . Holotype male ( NMW): "Eq. GUINEA, Bioko , // 0 3.3001, 0 0 8.6482, // 938m, 23.xii.2015, sift. //

for. lit., V.Grebennikov"; "DNA voucher // IBE-AN370"; aedeagus dissected and mounted on a transparent card pinned with the specimen, plus red holotype label. DNA extraction stored in the IBE with the same voucher number; COI with accession numbers LT707765 (COI-5', "barcode") and LT707761 (COI-3').

Paratypes. 8 males ( CHB, IBE, MCZ) 1 female ( NMW): same data as holotype, with red paratype labels . Female paratype used for DNA extraction with voucher number IBE-AN526, mounted after extraction on a card (COI-3' accession number LT707762 ). Four male paratypes stored in absolute ethanol in the IBE.

Description. length 1.34–1.50 mm (males), 1.54 mm (female paratype); width 0.60–0.70 mm (males), 0.70 mm (female paratype). Body form elongate, compact, maximum width of pronotum slightly smaller than maximum width of elytra ( Fig. 1 ). Body and appendages uniformly pale brown.

Head: Labrum strongly excised anteriorly, with lobes rounded. Surface smooth and shiny, margins finely reticulated, with fine and sparse punctures. Puncturation on clypeus slightly coarser than on labrum. Frontoclypeal suture slightly arcuate. Frons with a coarser and denser puncturation than on clypeus, slightly less dense on disk; distance between punctures approximately equal to their diameter; surface between punctures smooth and shiny. Eyes large, prominent.

Pronotum: Tranverse, lateral margins regularly curved, maximum width in middle part; clearly denticulate. Anterior and posterior margins slightly sinuated. Surface with coarse punctures, denser on the medial part, with two lateral bands almost without punctures; surface between punctures smooth and shiny.

Elytra: Approximately twice longer than pronotum; apex with margins finely serrated; with a broad explanate margin ending slightly before the apex, narrow at base, uniformly broadening towards apex; apex round. Ten very regular striae between suture and shoulder, with large and uniform punctures; punctures of apex of the elytra slightly less strong, with wider intervals. Interstriae smooth and shiny, slightly rugose at apex. Membranous wings well developed, longer than elytra.

Venter: Prosternum with distinct medial keel. Mesoventrite laterally bordered, apex truncated. Metaventral plaques densely and finely punctured, with a granulated appearance, covered by long hydrofuge pubescence; with two parallel glabrous areas on middle part, with smooth and shiny surface, without punctures. Abdominal sternites covered with fine punctures, space between punctures with fine transverse striolae; surface of abdominal sternites covered by short, recumbent pubescence, with exception of last three sternites, which are glabrous (other than marginal setae) and with a transverse polygonal reticulum, giving a dull appearance.

Sexual variation: Aedeagus ( Figs 3–4 ) with median lobe asymmetrical, straight; apex with digitiform expansions and a long membranous apical piece, somewhat resembling a hammer in lateral view; with two dorsal setae behind left paramere, not clearly seen in lateral view (not represented in Fig. 3 ). Left paramere very short and stout; right paramere longer, with apex recurved over the median lobe. Middle and hind tibia of most males slightly expanded, with external side curved ( Fig. 1 ).

Females larger and more robust than males. Glabrous areas of the metaventrite smaller, less elongated. Tibia with external side straight, not expanded. Elytral margins with a wider explanation. Spermatheca very large and elongate; basal apohyses of gonocoxites long and curved inwards. Although there seem to be some differences in the gonocoxites between the two species (in e.g. the general shape and the size of the pseudostyli), they do not seem to be significant enough to allow unambiguous identification without DNA data. Therefore we do not designate females for which there is no molecular data as paratypes (11 specimens in total).

Etymology. Named after the Bubi , a Bantu ethnic group native to Bioko. Name is a noun in apposition.

Distribution. So far only known from the type locality.

Habitat and ecology. All specimens were found by sifting litter in a mid-altitude primary forest, without large trees, during the dry season and with no free water in the vicinity. The single sample was taken over two days along a single trail through the forest. Actual sifting, however, was done in four places along the trail, with intervals of some 300 meters between them (thus extreme sampling spots might be about 1 km apart). The forest was somewhat similar along the trail, although some 150 meters altitudinal difference existed between extreme sampling spots (V. Grebennikov, personal communication, 2016). Some specimens have unidentified epibionts or ectoparasites on legs and palpi ( Fig. 1 ).

Figures

FIGURES 1 & 2. Habitus of 1) Hydraena (Hydraenopsis) bubi sp. n., male paratype and 2) H. (Hydraenopsis) grebennikovi sp. n., female paratype (voucher No. IBE-AN 577, mounted after DNA extraction). Scale bar: 1 mm.

FIGURES 3 & 4. Aedeagus of Hydraena (Hydraenopsis) bubi sp. n. (holotype) 3) lateral view, 4) ventral view. Scale bar = 0.1 mm.