Coelostoma (Lachnocoelostoma) nankunshanense Mai & Jia, 2022

Mai, Zuqi, Hu, Jian & Jia, Fenglong, 2022, Additional fauna of Coelostoma Brulle, 1835 from China, with re-establishment of Coelostoma sulcatum Pu, 1963 as a valid species (Coleoptera, Hydrophilidae, Sphaeridiinae), ZooKeys 1091, pp. 15-56 : 15

Coelostoma (Lachnocoelostoma) nankunshanense Mai & Jia sp. nov.

Figures 6A-F , 16G, K

Type material examined.

Holotype: male (SYSU), China, Guangdong, Longmen County, Nankunshan Mountain, Guanyintan (观音潭), 23°38'13"N, 113°51'1"E, 503.7 m, 24.iii.2021, Mai, Jiang, Yang & Huang leg. Paratypes: 14 spec. (SYSU), 2 spec. (IZCAS), same data as the holotype;

Diagnosis.

Length 4.7-5.0 mm. Head, pronotum and elytra with similar punctation. Prosternum carinate medially, with a prominent tooth anteromedially. Elytra slightly parallel-sided in the middle, without serial punctures laterally. Mesofemora densely pubescent, except on extreme apex. First abdominal ventrite with median carina on basal two-thirds. Fifth ventrite slightly emarginate and with a row of stout setae apically. Aedeagus (Fig. 6D-F ): similar to Coelostoma turnai Hebauer, 2006 ( Jia et al. 2014: fig. 21), but median lobe wider and shorter, outer face of parameres distinctly incised subapically.

Description.

Form and colour (Fig. 6A-C ). Total length 4.7-5.0 mm (holotype: 4.9 mm); maximum width 2.6-3.2 mm (holotype: 3.0 mm); body broadly oval, slightly parallel-sided in the middle, moderately convex. Dorsum black and shiny. Labrum, maxillary palpi and labial palpi reddish brown, antennae yellowish to reddish brown with dark club. Ventral surface reddish brown to black. Femora and tibiae dark reddish brown, tarsi pale reddish.

Head. Dorsal surface with dense fine punctures. Interstices between punctures smooth. Clypeus subtruncate anteriorly. Eyes of moderate size, distinctly emarginate anteriorly in lateral view, separated by ca. 3.5 × the width of one eye. Mentum strongly emarginated anteriorly and depressed in anterior half, with sparse punctures and dense transverse microsculpture. Antennae with nine antennomeres, antennal club (antennomeres 7-9) densely pubescent. Maxillary palpomere 2 strongly swollen, palpomere 4 truncate apically, slightly longer than palpomere 3. Gula narrow and glabrous.

Thorax. Pronotum widest posteriorly, gradually narrowed anteriad, with punctures as on head, anterolateral angles obtusely rounded, posterolateral angles blunt, anterior and lateral margins with narrow marginal bead. Prosternum with a carina medially and a prominent tooth anteromedially. Scutellum in shape of equilateral triangle, with punctures finer and denser than those on pronotum. Elytra with punctures as on pronotum, punctures on lateral and posterior portions somewhat coarser than those on disc; elytra without serial punctures; sutural stria reaching anterior third of elytra; lateral margin of elytra with bead but not explanate.

Legs. Pro- and mesofemora bearing dense pubescence, except on extreme apex. Metafemora not pubescent, with dense microsculptures and spares fine punctures. Meso- and Metatibia slightly flattened, with strong apical spurs and series of sparse stout spines laterally. Tarsi with long dorsal setae and gold ventral setae; metatarsi with fifth tarsomere almost as long as third and fourth combined. Claws curved, with a pair of long setae beneath.

Abdomen. Abdominal ventrites densely pubescent. First ventrite with distinct median carina on basal two-thirds. Fifth ventrite with fine marginal bead and slightly emarginate apically.

Male genitalia (Fig. 6D-F ). Aedeagus ca. 1.0 mm long. Median lobe widest basally, bottle-shaped with apex emarginate (depth of emargination are variable in individuals as in Fig. 6F ), ca. 1.8 × as long as wide; gonopore situated basally, wider than long; parameres slightly shorter than median lobe, distinctly incised on outer face subapically, broadly truncate apically

Etymology.

This species is named after the type locality, Nankunshan, a nature reserve in Guangdong Province.

Biology

(Figs 16G, K ). All specimens were collected at night on some large stones in a forest stream. Individuals feed on algal mat and mate on the habitat. Some individuals of Coelostoma bifidum Jia, Aston & Fikáček, 2014 were also collected together.

Distribution.

Only known from type locality. China (Guangdong).

Figures

Figure 6. Coelostoma (Lachnocoelostoma) nankunshanense Mai & Jia, sp. nov. A dorsal view B ventral view C lateral view D-F aedeagus D, E holotype D dorsal view E ventral view F aedeagus of a paratype (dorsal view). Scale bars: 1.0 mm (A-C); 0.5 mm (D-F).

Figure 16. Habitats of Chinese Coelostoma spp. A C. turnai Hebauer, 2006 active at wet rocky ground beside a river at night (Fujian) B C. sulcatum Pu, 1963 on sandy gutterway with shallow flowing waters at night (Guangdong) C C. phallicum Orchymont, 1940 hided under a brick beside the wastewater during the day (Guangdong) D C. phallicum Orchymont, 1940 dived under water and fed on algal mats at night (Guangdong) E C. bifidum Jia, Aston & Fikacek on wet stone wall at night (Guangdong) F C. sulcatum Pu, 1963 on muddy edge of artificial lake at night (Yunnan) G C. nankunshanense sp. nov. on a stone in the middle of a forest stream at night (Guangdong) H C. surkhetensis Hebauer, 2002 in a wet stone on the edges of a forest stream at night (Xizang) I C. wui Orchymont, 1940 on the edges of a mountain river at night (Shanxi) J C. sulcatum Pu, 1963 on muddy edges of brackish lagoon at night, with a marine Amphipoda beside it (Macao) K C. nankunshanense sp. nov. mating at night (Guangdong) L C. wui Orchymont, 1940 ovipositing eggs on wet land at night (Shanxi).