Copelatus mkambati, Bilton & Mlambo, 2022

Bilton, David T. & Mlambo, Musa C., 2022, A new Copelatus with small eyes from the Eastern Cape Wild Coast, South Africa (Coleoptera: Dytiscidae), Acta Entomologica Musei Nationalis Pragae 62 (1), pp. 15-21 : 17-20

Copelatus mkambati sp. nov.

( Figs 1–4 )

Type material. Hඈඅඈඍඒඉൾ: J, ‘ 7/ix/2019 South Africa EC / Mkambati Nature Reserve / Mgwegwe River / 31°17’ 36.28”S / 29°59’50.83”E, 58 m / Wet 211, D T Bilton leg.’ ( AMGS). With red Holotype label. Pൺඋൺඍඒඉൾඌ: 1 J ( CDTB), same data as holotype; 1 ♀, ‘ 9/ix/2019 South Africa EC / Mkambati Nature Reserve / Diwa River / 31°17’ 44.49”S / 29°58’52.15”E, 57 m / Wet 215, D T Bilton leg.’ ( AMGS). With red Paratype labels.

Description. Male (holotype). Body shape ( Fig. 1A ) elongate, subparallel, relatively flat; head relatively large and broad. Head testaceous; infuscated at anterior margin of clypeus, around clypeal suture, and eyes; very weak infuscation towards posterior temples. Pronotum testaceous with faint infuscation on disc and irregular row of dark spots visible through cuticle inside anterior and posterior margins. Elytra testaceous; each elytron weakly infuscated over most of area inside outer stria, with the exception of narrow, paler region adjacent to suture. Dark line visible through cuticle outside this pale strip, breaking down into spots along base and close to apex. Venter testaceous, prosternum, prosternal process and margins of cuticular plates infuscated; all appendages testaceous.

Head broad, width 0.77 pronotal width ( Figs 1A , 4A ) shining, microreticulate, meshes isodiametric on frons and vertex, elongate laterally on temples; finely micropunctate, most micropunctures bearing short, peg-like setae, some with long, fine, adpressed setae. Eyes small, occupying approximately one fourth side of head, with 9–11 ommatidia in longest series. Pronotum ( Figs 1A , 2A ) shining, isodiametrically microreticulate and micropunctate as head; with fine impressed longitudinal strioles, densest and longest laterally and posteriorly, sparsest and shortest on disc. Disc with shallow, weakly impressed longitudinal furrow in central fourth. Puncture row behind anterior pronotal margin irregular, shallow and weakly evident, most punctures with fine, adpressed amber-coloured setae; similar punctures and setae close to lateral and posterior margins. Each elytron with two well-impressed discal striae, extending from base to ca. 0.1 from apex. Each stria with sparse, medium punctures, bearing long, amber-coloured setae. No submarginal stria; irregular row of longitudinal strioles and punctures, the latter bearing long, fine, adpressed setae, present on anterior 0.6 of outermost elytral edge, where submarginal striae are typically located in Copelatus . Elytral disc between striae ( Fig. 2A ) shining, sculptured as pronotum; strioles much sparser outside of second stria, and almost absent in posterior fourth, where reticulation is somewhat obsolete and more transverse than on disc. Legs with basal three pro- and mesotarsomeres dilated, each foot bearing four transverse rows of suction setae. Protibiae broadly expanded distally.

Venter weakly shining; finely microreticulate and micropunctate. Microreticulation meshes mostly small and isodiametric; transverse on metaventrite, elongate on metacoxae. Lateral wings of metaventrite narrow. Metacoxae with sparse, elongate, longitudinal strioles. Metacoxal lines well impressed, becoming finer towards metaventrite and absent in basal fifth of metacoxae. Abdominal ventrites I– III with narrow, elongate, fine longitudinal ridges laterally, particularly marked on ventrite II. Abdominal ventrite IV with irregular transverse row of punctures halfway down length, each bearing a long, fine, adpressed seta. Abdominal ventrite VI with cluster of small punctures laterally, halfway down length, each bearing similar setae.

Male genitalia. Median lobe of aedeagus ( Fig. 3C ) relatively simple, evenly curved in lateral view, with small oval opening medially on right side (see right hand lateral view in Fig. 3C ). Rather straight in ventral view; apex flattened and bluntly pointed. Paramere as in Fig. 3C .

Measurements. Holotype: BL 3.9 mm; BL-H 3.45 mm; EL 2.7 mm; EW 1.50 mm. Paratypes: J BL 4.0 mm; BL-H 3.5 mm; EL 2.8 mm; EW 1.65 mm. ♀ BL 4.3 mm; BL-H 3.65 mm; EL 3.0 mm; EW 1.75 mm.

Female ( Fig. 1B ) coloured as male; dorsum matt, reticulation ( Fig. 2B ) much more strongly impressed than male; meshes larger throughout, isodiametric to elongate on head, slightly elongate on pronotum, elongate on elytral disc, strongly transverse in posterior fourth. Micropunctation as male. Strioles denser, deeper and longer than in male, also present on frons and vertex of head, where they are orientated transversally centrally and longitudinally posteriorly and laterally. Protibiae less expanded distally. Venter as male, but with strioles on metacoxae very sparse and longitudinal ridges on abdominal sternites weaker and sparser. The single female paratype is somewhat larger and broader than the two known males (see above).

Differential diagnosis. A member of the C. macellus species group on the basis of elytral striation, the new species can be distinguished from the two other Afrotropical species with two discal striae as follows. In contrast to C. mkambati sp. nov. and C. macellus , C. basilewskyi lacks longitudinal strioles, being microreticulate and micropunctate only dorsally. Compared to C. macellus ( Fig. 1C ), C. mkambati sp. nov. is more elongate, paler in colouration, with longer, denser strioles dorsally and finer, less strongly impressed, micropunctation on the elytra, particularly in the posterior third. The three species can also be readily distinguished on the form of their median lobes (see Fig. 3 ). Additionally, C. mkambati sp. nov. has relatively small eyes, with only 8–11 ommatidia in the longest series. In contrast, the holotype of C. macellus ( Fig. 1C ) has visibly larger eyes, with 18 ommatidia in the longest series. Although we have not been able to study specimens, the description of C. basilewskyi makes no mention of the compound eyes, strongly suggesting that these are also normally sized for the genus.

Etymology. The new species is named after Mkambati, a beautiful Nature Reserve of natural grassland, forests and wetlands on Natal Group Sandstones in the Pondoland region of the Eastern Cape Province, from which all known specimens have been collected. The specific epithet is a noun in the nominative singular.

Distribution and ecology. Known to date only from two close localities in the Mkambati Nature Reserve, Eastern Cape Province, South Africa. Mkambati is on the Pondoland Wild Coast, whose sandstones and forested gorges support a high number of endemic taxa (Mඎർංඇൺ et al. 2006), and is part of the Maputaland-Pondoland-Albany Global Biodiversity Hotspot (Mංඍඍൾඋආൾංൾඋ et al. 2004, Pൾඋൾඋൺ et al. 2011). The invertebrate fauna of the entire Wild Coast region remains poorly studied, even compared with other areas in southern Africa (Hൺආൾඋ & Sඅඈඍඈඐ 2017). Recent surveys of aquatic beetles in this region have yielded several new species (e.g. Bංඅඍඈඇ 2016, 2020; Bංඅඍඈඇ & Mඅൺආൻඈ, in press) and often high alpha diversity (Pൾඋංඌඌංඇඈඍඍඈ et al. 2016, Bංඋൽ et al. 2017). All three known specimens were collected from the flooded margins of small streams, in areas where seepage water was entering from nearby small valley wetlands. At the type locality, specimens were taken a day after heavy rainfall, when seepage flow was relatively strong. A return visit four days later, when water levels had receded, produced no further specimens despite an extended search.

Figures

Fig. 1. Copelatus species.A – C. mkambati sp. nov. holotype male habitus; B – C. mkambati sp. nov., paratype female habitus; C – C. macellus Guignot, 1950, holotype male habitus; D – C. macellus, holotype labels. Scale bar applies to A–C. Figs C & D: © MNHN/Christophe Rivier.

Fig. 2. Copelatus mkambati sp. nov. dorsal sculpture. A – holotype male; B – paratype female.

Fig. 3. Copelatus species male genitalia. A – C. macellus Guignot, 1950, median lobe; B – C. basilewskyi Bilardo & Pederzani, 1979, median lobe; C – C. mkambati sp. nov., median lobe and paramere. Scale bar in C = 0.5 mm. Note that lines on the paramere represent musculature, not surface ridges. A & B after GඎංGඇඈඍ (1961) and Bංඅൺඋൽඈ & Pൾൽൾඋඓൺඇං (1979), respectively.

Fig. 4. Southern African Copelatus species compound eyes, all to same scale. A – C. mkambati sp. nov., paratype male; B – C. capensis Sharp, 1882 (Groote River, South Africa); C – C. erichsoni Guérin-Méneville, 1847 (St Lucia, South Africa); D – C. pulchellus (Klug, 1834) (St Lucia, South Africa).