Sharphydrus kamiesbergensis, Bilton, 2013

Bilton, David T., 2013, A taxonomic revision of South African Sharphydrus, with the description of two new species (Coleoptera: Dytiscidae: Bidessini), Zootaxa 3750 (1), pp. 26-36 : 31-34

Sharphydrus kamiesbergensis sp. nov.

( Figs 1B – 3B )

Type locality. South Africa, Northern Cape, Kamiesberg, stream on Witwater-Langkloof road ca. 1 km S of junction, 30 23 42.96S 18 08 08.40E, 1097 m. ( Fig. 3B ) .

Type material. Holotype (male): “ 19/ix/2010 South Africa NC, Kamiesberg, stream on Witwater-Langkloof road ca. 1 km S of junction, D. T. Bilton leg.” (genitalia extracted and mounted in DMHF on same card) with red printed holotype label “ Holotype Sharphydrus kamiesbergensis sp. nov. Bilton” ( ISAM).

Paratypes (7♂, 6♀): Same data as holotype (2♂, 1♀ CDTB; 1♂, 1♀ NMW; 1♂, 1♀ UMO; 1♂, 1♀ ISAM; 1♂, 1♀ DMSA; 1♂, 1♀ SANC). With red printed paratype labels “ Paratype Sharphydrus kamiesbergensis sp. nov. Bilton” .

Description. Size: Holotype: body length (to elytral apices) 2.85 mm; max. width (elytra) 1.45 mm. Elytral length 2.1 mm. Same values for paratypes 2.8–3.0, 1.45–1.5 and 2–2.25 mm respectively.

Colour ( Fig. 1B ): Dorsal surface predominantly pale straw yellowish brown. Head and pronotum slightly more deeply pigmented than ground colour of elytra. Hind margin of pronotum with well-marked black band, this being thickest between lateral plicae, here approximately 1/6–1/5 pronotal length in extent. Black band narrower towards centre of pronotum, giving it a distinctly undulating appearance. Front margin of pronotum entirely pale. Elytra with diffuse dark markings, with rather ill-defined boundaries. Sublateral dark markings more well defined, present just behind middle, and just before apex. Palpi and legs uniformly pale yellowish brown. Antennae also pale yellowish brown, with segments 7–11 infuscated apically, this being particularly marked in segment 11. Venter pale yellowish brown, somewhat darkened around ventral junctions and coxal insertions.

Head: Broad, with large eyes. Clypeus somewhat thickened and evenly rounded, but lacking anterior border, and not separated from rest of head. Well-developed shallow, open fovea present on each side of head, anterior to eye, just behind clypeus. Cervical line well marked between hind portion of eyes. Head in front of cervical line with distinct, coarse punctures, each bearing a small peg-like seta at its centre. Punctures smaller and sparser on clypeus, here 2–3 puncture widths apart; becoming larger and denser towards cervical line, here approximately 3x diameter of those on anterior clypeus, and spaced 1/3–1/2 puncture width apart. Head microreticulate except on smooth central frons,. Microreticulation transverse on clypeus and behind cervical line; isodiametric elsewhere. Apical segments of maxiliary and labial palpi narrowly truncate, and somewhat flattened dorsoventrally at apices.

Pronotum: Transverse rectangular. Sides rounded to front angles, straight behind; widest just before middle. Hind margins distinctly bisinuate around middle. Lateral plicae well developed, relatively deep, and open interiorly. Plicae deepest at posterior ends; sinuate and becoming shallow anteriorly, here extended to approximately 1/3 away from front margin of the pronotum. Pronotal surface rough, with a coriaceous appearance, due to coarse, dense, sometimes almost confluent punctation, each puncture bearing a small peg-like seta as on head. Punctures particularly dense towards centre of pronotal disc, here separated by ridges only. Pronotal surface smooth between punctures; without visible microreticulation.

Elytra: Together forming an elongate oval, with point of maximum width around middle. Lateral margin rounded to front angles, somewhat subparallel in middle, and tapered towards apex in posterior half. Elytra with well-developed discal keels running posteriorly from base of pronotal lateral plicae to a point just over halfway along elytral length. Carinae robust; maximum height being towards middle of keel. Elytral suture also raised over discal region; area between keels and suture relatively flat ( Fig. 1B ). Elytral tracheation clearly visible in dry specimens. Each elytron with a row of long, fine, recumbent setae interior to keel, positioned approximately 1/3 way towards suture, and running for length of keel (setae apparently lost and invisible in some paratypes). Entire elytral surface, including keels, with dense, coarse punctation, giving a coriaceous appearance. Punctures almost confluent in places (e.g. close to keels), and each puncture bearing a small peg-like seta. No visible microreticulation between punctures.

Venter: Anterior margin of prementum with short, stout setae and scattered longer hair-like setae behind. Mentum will well developed blunt truncated medial tooth. Surface of mentum with fine transverse ridges, but otherwise lacking apparent microreticulation. Submentum with transverse furrows and scattered punctures, but lacking microreticulation. Gular sutures weak, but gular region distinct due to absence of microreticulation. Remainder of underside of head with distinct isodiametric reticulation, obsolete on genae and towards outer margins of mandibles. Pronotal hypomeron smooth and shining, with very few scattered punctures. Prosternum smooth and shining with scattered punctures, becoming dense and almost confluent at base of prosternal process, an area also furnished with long, hair-like setae. Prosternal process strongly raised, neck of process forming an angle of approximately 70° with prosternum. Process elongate, cordiform, flat, with a broad shallow groove occupying 3/4 of process width. Neck of process with long, hair-like setae; process itself with punctures bearing short, peg-like setae. Prosternal process reaching anteromedial process of the metaventrite. Metaventrite with weakly defined groove in rear half. Coxal lines well-marked, subparallel, diverging anteriorly. Hind coxal margin bisinuate; coxal lobes weak, not covering leg insertions. Ventral surface of meso- and metathorax and abdomen, elytral epipleurs with dense, coarse punctation, each puncture bearing a short peg-like seta. Punctures very dense and almost confluent on hind coxae and abdominal ventrites; elsewhere spaced at most 1–1.5 puncture widths apart. Punctures absent only from hind margins of hind coxae, where traces of isodiametric microreticulation are visible; spaces between punctures otherwise smooth. Fourth and fifth abdominal ventrites with long hair-like setal bunches at their centres.

Aedeagus: Median lobe characteristically shaped and pigmented ( Fig. 2B ); trilobate at apex, with a curved, ventrally-directed process. Median lobe deeply pigmented, black, with exception of apical median process, this dark colouration being present in fresh and preserved specimens. Parameres ( Fig. 2B ) two-segmented, with bluntly curved, hooked tips.

Females: As males except punctures on pronotum somewhat sparser, with some isodiametric microreticulation visible between them. Similar, but much weaker and somewhat obsolete reticulation visible between elytral punctures. Fore and mid tarsi narrower and slightly shorter than in males, particularly last tarsal segment.

Variability. Paratypes vary slightly in size (see above) and the development of the elytral pattern, some specimens being darker than the holotype.

Distribution. To date only known from the type locality ( Fig. 3B ), a small stream flowing through Kamiesberg Granite Fynbos/Renosterveld (sensu Mucina & Rutherford 2006). The high valleys and summits of the Kamiesberg range represent an isolated, northern outpost of the fynbos biome in relatively arid Namaqualand, and support other endemic aquatic beetles, including Andex insignis Sharp, 1882 ( Challet & Turner 2006).

Etymology. Named after the Kamiesberg, an isolated granite massif in Namaqualand. The specific epithet is an adjective in the nominative singular standing in apposition.

Ecology. Specimens were netted from relatively deep (ca. 60 cm) water over gravel and silt in a pool immediately below a short riffle in a stream ( Fig. 3B ). They occurred together with the water beetles Sharphydrus coriaceus , Canthyporus hottentottus (Gemminger & Harold) , Andex insignis , Agabus ruwenzoricus and Nebrioporus sp. One of the females collected retained an intact spermatophore tail, indicating recent mating activity.

Figures

FIGURE 1. Habitus of A) Sharphydrus brincki sp. nov. B) S. kamiesbergensis sp. nov. C) S. capensis. D) S. coriaceus. Dorsal and lateral views. Scale bar = 1 mm.

FIGURE 2. Male genitalia of Sharphydrus species: median lobe in lateral and ventral view, right paramere of: A) S. brincki sp. nov.; B) S. kamiesbergensis sp. nov.; C) S. capensis; D) S. coriaceus. Scale bar = 0.5 mm

FIGURE 3. Type localities of: A) Sharphydrus brincki sp. nov. South Africa, Western Cape, Cederberg, Matjiesrivier Reserve, Matjies River ca. 3 km N of Cederberg Oasis; B) S. kamiesbergensis sp. nov. South Africa, Northern Cape, Kamiesberg, stream on Witwater–Langkloof road ca. 1 km S of junction. Photos D.T. Bilton.