Protozantaena gigantea, Bilton & Mlambo, 2024

Bilton, David T. & Mlambo, Musa C., 2024, A distinctive new species of Protozantaena Perkins, 1997 from lowland Namaqualand, South Africa (Coleoptera, Hydraenidae), Zootaxa 5424 (3), pp. 383-388 : 384-386

Protozantaena gigantea sp. nov.

( Figs. 1C & F , 2 )

Type locality. South Africa, Northern Cape Province, Namaqualand, Swart Doring River on N7, ca. 30 km south of Garies, residual pools, 30° 49’ 25.05” S 18° 07’ 05.09” E, 169 m.

Type material. Holotype (male): “ 17/ix/2023 South Africa NC// Swart Doring River on N7, ca. // 30 km south of Garies 304925.05S // 180705.09E 169 m D T Bilton leg.” and red holotype label ( AMG).

Paratypes (7): 1♂, 6♀ same data as holotype ( AMG, CDTB, NMW) .

Description. Size: Holotype: BL 1.95 mm; EL 1.25 mm; EW 0.85 mm. Paratypes: Male BL 1.95 mm; EL 1.25 mm; EW 0.86 mm. Females BL 1.95–2.00 mm; EL 1.25–1.30 mm; EW 0.85–0.90 mm.

Colour: Dorsum ( Fig. 1C ) brown to dark brown; pronotal and elytral margins paler. Antennae, maxillary palpi and legs yellowish brown; tarsi and last segment of maxillary palps infuscates. Venter brown; pronotal hypomeron and elytral epipleurs paler.

Head: Labrum transverse, large, rectangular, slightly longer than clypeus; apical margin upturned, with weak apicomedian emargination; laterally fringed with short arcuate setae; dorsal surface shining, microreticulation absent, with sparse, fine micropunctation and long, sparse, fine adpressed setae. Frontoclypeal suture distinct, weakly arcuate. Clypeus, frons and vertex shining, with sparse, medium punctures bearing long, fine, adpressed setae, Microreticulation weak and restriced to lateral border of clypeus and frons between interocular foveae and compound eyes. Ocelli large and distinct, shining, each located at the base of shallow, oblique interocular fovea, which extend towards, but fail to reach, frontoclypeal suture. Compound eyes relatively large; 12 ommatidia in longest series. Maxillary palpi moderately long, last palpomere elongate, widened slightly subbasally, then narrowed basally on anterior surface.

Pronotum: Transverse, widest before middle. Anterior margin weakly arcuate; median 0.25 with distinct hyaline border; posterior margin weakly bisinuate around centre; lateral margins weakly attenuated and sinuate behind widest point, anteriorly arcuate to anterior angles; in lateral view appearing thickened over wider anterior section, with upper and lower rim. Anterior angles broadly rounded, posterior angles weakly obtuseangulate. Anterior and posterior impressions shallow but evident, relatively straight. Without impression at posterior angles. Surface strongly shining, especially on disc, microreticulation absent. Entire surface punctate, each puncture with anterior margin extended posteriorly as narrow ridge, apparently dividing puncture into a pair of two smaller punctures; long, fine, recumbent setae arising from posterior extreme of dividing ridge. Punctures denser towards lateral margins, less so along anterior and posterior margins; very shallow and sparser on disc.

Elytra: Elongate, attenuate posteriorly. Sides arcuate, explanate margins relatively broad in middle; apices broadly truncately rounded. Ten-seriate punctate; punctures without granules, series not striate-impressed; punctures moderate, round, shallow, each bearing small, fine, white, recumbent or decumbent seta; spacing between punctures approx. 1–1.25 puncture diameters on disc. Interstices shining, each with unilinear row of fine, punctures, bearing long, fine, recumbent setae, similar to those of puncture rows; punctures without granules.

Venter: Mentum, submentum, and genae shining, microreticulation absent; mentum with moderate, submentum with sparse, medium punctures, bearing fine, white decumbent setae; genae almost impunctate. Gula shining with sparse with sparse micropunctures and transverse lines of reticulation. Prosternum rugosely microreticulate; punctate anteriorly and laterally, punctures bearing erect golden setae, particularly long centrally; mesoventrite rugosely microreticulate, punctate, with short, erect setae. Pronotal hypomeron broad, glabrous, with sparse, fine punctures and short adprssed setae. Elytral epipleurs broad anteriorly, narrowing over posterior 0.6 and absent at apices; surface shining, glabrous; anterior 0.3 with irregular, confluent punctures and suberect setae along internal margin, otherwise without evident microreticulation or punctation. Metaventrite dull, with dense, medium punctures bearing shaggy hydrofuge vestiture; with shallow, longitudinal oval impression in centre, surrounded by flat area. Abdominal ventrites 1–4 punctate as metaventrite and completely hydrofuge pubescent, some longer hairs scattered amongst shorter vestiture and along posterior margins of ventrites; ventrite 5 with pubescence over anterior 0.5 only; ventrites 5–7 shining, each with an irregular transverse row of punctures, some bearing long, yellowish, decumbent setae. Last tergite with tuft of setae on each side of narrow, shallow apicomedial notch.

Legs: Moderately long, tarsal segments relatively narrow and elongate. Basal three tarsomeres of pro and mesotarsi with pad of suction setae.

Aedeagus: Elongate ( Fig 1F ), gonopore bearing flagellum very long, arcuate, bending toward base, almost as long as main-piece; supporting flagellum shorter. Mainpiece straight or nearly so in ventral view, narrowing approx. 0.3 from apex; in lateral view arcuate, with relatively large, broad, widened setose area; parameres very short, each with two setae.

Female: Without obvious external differences to males, other than the absence of tarsal suction setae.

Variation: Some paratypes paler than holotype due to tenerality.

Differential diagnosis. In the field, the size and appearance of P. gigantea sp. nov. suggested a species of Parhydraena Orchymont, 1937 , it first being recognised as a Protozantaena on the aedeagus. The detailed morphology of the new species suggests that it is related to P. birdi and P. labrata , known from the Eastern Cape Great Escarpment and Central Namibia respectively, sharing with these species the same general habitus, male labral modifications, maxillary palpal structure and aedeagal design. The new species differs markedly in size, however, at 1.95–2.00 mm being significantly larger than either P. birdi (1.40–1.50 mm) or P. labrata (1.40–1.45 mm)—see Fig. 1A–C . In addition, P. gigantea sp. nov. has shallower, finer punctures, particularly on the head and pronotum, than either P. birdi or P. labrata , as well as relatively longer maxillary palpi and legs and more broadly explanate elytral margins. The aedeagus of P. gigantea sp. nov. also differs consistently from that of P. birdi and P. labrata , being larger in P. gigantea sp. nov., with the main piece thicker in lateral view, a larger, more strongly widened setose area close to apex, and shorter flagellae. Note that the length and angle of curvature of the flagellae differ between specimens within both P. birdi and P. labrata . This may also be the case with P. gigantea sp. nov., but so far only two males are available for study.

Etymology. Named in reference to the relatively large body size.At 1.95–2.00 mm in length, this Protozantaena could be considered a giant amongst dwarves, particularly in a mainland African context, the next largest known species being the Madagascan P. elongata Perkins, 2017 , ranging from 1.73 to 2.00 mm. For comparative body sizes of African species, see Fig. 1A–C .

Distribution and ecology. Known only from the type locality, the Swart Doring River, a seasonal watercourse in lowland Namaqualand, part of the Groen River catchment. At the time of sampling, water in the Swart Doring was limited to residual pools, around which there were small traces of salt incrustation. P. gigantea sp. nov. was found in a single residual pool below an old bridge ( Fig. 2B–C ). The water beetle fauna suggested fresh to weakly hyposaline conditions, accompanying species being the dytiscids Caperhantus cicurius (Fabricius, 1787) , Cybister tripunctatus africanus Laporte, 1835 , Hydroglyphus infirmus (Boheman, 1848) , Tyndalhydrus caraboides Sharp, 1882, Canthyporus hottentottus (Gemminger & Harold, 1868) and Andex insignis Sharp, 1882 , and the hydraenids Ochthebius andronius Orchymont, 1948 , O. pedalis Balfour-Browne, 1954 , O. spinasus Perkins & Balfour-Browne, 1994 , Hydraena duodecimata Perkins, 2014 and Parasthetops striatus Perkins, 2008 . The new Protozantaena has never been found elsewhere in the region, despite rather extensive water beetle sampling in the Kamiesberg and Bokkeveld in recent years (see Bilton 2013a,b; 2015; 2016; 2017). On current data it seems that P. gigantea sp. nov. may be restricted to highly seasonal rivers in the Namaqualand lowlands. Seasonal rivers in the region harbour other locally endemic water beetles, including the torridincolids Delevea madiba Bilton & Mlambo, 2023 and D. namaqua Bilton & Mlambo, 2023 , these taxa being apparently related to D. namibiensis Endrödy-Younga, 1997 , known from the South African Great Escarpment (Clarke et al. 2011) and the same region of Namibia as P. labrata . Such distribution patterns suggest that common historical factors have shaped the evolution of these two lineages of beetles (see Bilton & Mlambo 2023). Another similarity with Delevea Reichardt, 1976 is that the largest species known to date, D. namaqua , was found in Groen River catchment.

Figures

FIGURE 1. Protozantaena species.A) P. labrata Perkins, 1997, paratype, Namibia, Naukluft, habitus; B) P. birdi Bilton, 2022., holotype habitus; C) P. gigantea sp. nov. holotype habitus; D) P. labrata, paratype, Namibia, Naukluft, aedeagus; E) P. birdi, holotype aedeagus; F) P. gigantea sp. nov. holotype aedeagus. Scale bars A–C) = 0.5 mm; D–F) = 100 μm. Note that the exact curvature of the aedeagal flagellae differs between specimens of all three species.

FIGURE 2. Protozantaena species, distribution and habitat.A) Distribution of Protozantaena in Southern Africa, green symbol = P. gigantea sp. nov., red symbol = P. labrata Perkins, 1997, blue symbols = P. birdi Bilton, 2022, star indicating new locality in the Eastern Cape Drakensberg; B–C) Type locality and habitat of P. gigantea sp. nov., South Africa, Northern Cape Province, Namaqualand, Swart Doring River on N7 ca. 30 km south of Garies (photos Andy Foggo).