Hydrobiomorpha perissinottoi, Bilton & Pl, 2016

Bilton, David T. & Pl, Plymouth, 2016, A new species of Hydrobiomorpha from iSimangaliso Wetland Park, South Africa (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae 56 (1), pp. 149-157 : 150-156

Hydrobiomorpha perissinottoi sp. nov.

( Figs 1–6 , 9, 12 )

Type material. HOLOTYPE: J, SOUTH AFRICA: KWAZULU- NATAL: “ 6/ii/2015 South Africa KZN / St Lucia iSimangaliso Wetland / Park Eastern Shores 6- 28° 18’/ 59.84” S 32° 26’ 10.83” E D T Bilton ” (genitalia extracted and mounted on same card) and red holotype label ( TMSA) . PARATYPES (7 spec.): SOUTH AFRICA: KWAZULU- NATAL: 1 J, 2♀♀ same data as holotype. 1 J, “ 4/ii/2015 South Africa KZN / St Lucia iSimangaliso Wetland / Park Western Shores 1- 28° 14’/ 14.94” S 32° 24’ 32.06” E D T Bilton”. 1 ♀, “ South Africa KZN / St Lucia iSimangaliso Wetland / Park False Bay 5- 28° 0‘/ 51.70“ S 32° 21‘ 56.36“ E D T Bilton”. 1 J, 1 ♀ “ 4/ii/2015 South Africa KZN/ St Lucia iSimangaliso Wetland / Park Western Shores 5- 28°17’/ 44.79” S 32°22’58.83” E D T Bilton”. All with red paratype labels ( AMGS, CDTB, NMW, SAMC, SANC).

Description. Size. Body length 17.6–19.5 mm; elytral length 11.5–13.6 mm; elytral width 8.2–9.3 mm. Colour. Dorsum ( Fig. 1 ) dark brown to black, with aeneous green tones, particularly on basal 0.6 of labrum, on anterior part of clypeus, along frontoclypeal suture, hind margin of pronotum and on scutellum. Mandibles clear reddish-brown. Antennae with scape straw yellow; pedicel yellow basally, reddish infuscation in distal half; intermediate segments and cupule straw yellow; club black, except for long yellow setae. Maxillary palpi straw yellow; apical segment infuscated. Labial palpi yellow. Legs dark brown to black; tibial spurs and tarsi paler, especially apically. Venter dark brown to black; prosternal carina paler, reddish brown.

Head. Labrum strongly transverse, rounded apicolaterally with broad, shallow apicomedian emargination. Surface shining, no microreticulation, with double ground punctation; medium, shallow, medium punctures and close, shallow, fine punctures approximately 0.2 diameter of medium punctures. Two distinct pits either side of mid-line approximately 0.6 from apex, each bearing a cluster of trichobothria. Row of 5–6 systematic punctures immediately in front of posterior margin, either side of mid-line. Anterior margin of clypeus broadly emarginated, exposing thin membrane. Clypeus and frons shining, without microreticulation. Ground punctures in most areas of four distinct sizes: very sparse, moderate punctures; sparse, moderate punctures, diameter 0.5 previous; moderate, fine punctures, diameter 0.5 previous; close, very fine punctures, diameter 0.3 previous. Systematic punctures strong on clypeus and around inner margins of compound eyes, most with trichobothria. Compound eyes large, occupying approximately 0.4 lateral margin of head.

Pronotum arched, transverse, broadest at hind margin and narrowed to anterior angles. Anterior margin arcuate; posterior margin bisinuate around centre. Lateral margins narrowly beaded, bead ending just inside anterior angles. Anterior angles obtusely rounded; posterior angles broadly rounded. Surface shining, without microreticulation and with ground punctation as on clypeus and frons. Systematic punctures distinct, somewhat smaller than on head.

Elytra elongate oval, broadest just behind middle. Subparallel over anterior 0.6 then evenly rounded to apex; weakly emarginated at suture. Anterior and lateral margins beaded, bead broadest at shoulder and over anterior 0.6, then narrowing to apex. Surface shining, with fine, shallow isodiametric microreticulation and moderate, fine to very fine ground punctures; punctures varying in size, punctation not clearly double. Very shallow, irregular circular depressions also evident on disc. Irregular field of rather dense, moderate punctures interior to lateral bead ( Fig. 8 ), from shoulder to apex; each puncture with short, peg-like seta in anterior 0.5, seta not usually emerging from puncture. Systematic punctures in five rows, outer row mixed in with lateral puncture field. First row of systematic punctures slightly impressed. Systematic punctures also present along elytral margin in posterior 0.3.

Venter. Mentum shining, with moderate, coarse punctures and longitudinal wrinkles, directed anterolaterally, in lateral 0.3. Submentum shining, with sparse, moderate punctures and very close, very fine punctures, diameter approximately 0.2 previous. Submentum and anterior portion of gula excavated, forming an elongate bowl. Gula shining, wrinkled, with hydrofuge pubescence. Genae shining, wrinkled and glabrous either side of gula; pubescent laterally. Prosternum shining, with hydrofuge pubescence, punctate, punctures bearing long, yellow erect setae. Prosternal carina glabrous, projecting slightly anteriorly. Prosternal process acuminate, directed posteroventrally, ending halfway along procoxae. Mesoventrite and metaventrite ( Figs 4, 6 ) covered with hydrofuge pubescence, except on keels. Mesoventral keel with small anterior notch; continuous posteriorly with keel of metaventrite. Metaventral keel ( Figs 4, 6 , 11 ) produced into horizontal spine posteriorly, slightly arched ventrally just in front of spine, spine slightly dorsally directed, with distinct central keel ( Fig. 11 ). Apex of spine just surpassing posterior margin of abdominal ventrite 1. Abdominal ventrites 1–4 entirely covered in hydrofuge pubescence; abdominal ventrite 5 with median, longitudinal glabrous patch occupying posterior 0.6 of segment.

Aedeagus. Elongate, with rounded basal piece ( Fig. 14 ). Parameres elongate, narrow, sinuous to apex, with single, laterally-directed spine. Median lobe with ventral ornamentation consisting of apical hood and thin, hooked process, followed by low, narrow raised strip running for much of length. Aedeagal membranes well developed dorsolaterally, expanding to partially envelop the distal 0.5 of median lobe. Female. As male, except for somewhat flatter metaventral keel, and slightly longer metaventral spine, which lacks the central keel ( Figs 5, 7 ). Variation. Paratypes vary somewhat in body size and in the development of the shallow circular depressions on the elytral disc, but are otherwise almost identical.

Differential diagnosis. The new species would key to H. celata celata Mouchamps, 1959 and H. occidentalis Balfour-Browne, 1939 in MOUCHAMPS (1959) and HEBAUER (2006), on the basis of the metaventral spine, which extends beyond the posterior margin of abdominal ventrite 1, but does not reach the posterior margin of ventrite 2, the irregular puncture field along the lateral elytral margins ( Figs 8–10 ) and the presence of a large glabrous patch on abdominal ventrite 5. I have examined the holotype, 12 paratypes (IRSNB) and 7 additional specimens (BMNH) of H. celata celata , a taxon described from the Democratic Republic of the Congo and reported from Ethiopia, Burundi, Gabon, Malawi, Mozambique, Rwanda, Zambia, Sudan and Uganda ( Hebauer 2006). In addition to the nominotypical form, H. celata namibiensis Hebauer, 2006 was described on the basis of females from Kavango and the Caprivi Strip in northeastern Namibia. It differs from H. celata celata in the shape of the metaventral spine, and the single row of punctures along the elytral margin. This is also clearly not H. perissinottoi sp. nov., although its status as a subspecies of H. celata may change once males become available. I have also examined the holotype, paratype and one additional specimen of H. occidentalis (BMNH) , a species described from Nigeria and later reported from Egypt, Sudan and Tanzania. The additional specimen in the BMNH is a male labelled “Sobat River / Egypt / Zaphiro / 1905-252”, a locality in what is now South Sudan. It is not part of the type series and has been labelled as H. wencki by d’Orchymont, but more latterly (1958) identified as H. occidentalis by J. Balfour-Browne, a determination with which I concur. On external and aedeagal morphology, the new species is closest to H. occidentalis , although its larger size and darker colouration mean it superficially resembles H. celata celata . At 17.6–19.5 mm, H. perissinottoi sp. nov. is somewhat intermediate in size between the two species ( H. celata celata 18–23 mm, H. occidentalis 15–16 mm), but most closely resembles H. celata celata . BALFOUR- BROWNE (1939) mentions a female specimen from Nigeria 20 mm long, which he considers likely to be H. occidentalis , but excludes from the type series. I have been unable to find this specimen in the BMNH, which may belong to another species. The metaventral spine of the new species most closely resembles that of H. occidentalis in relative length, that of H. celata celata being longer (see Figs 11–13 ). Both H. occidentalis and H. perissinottoi sp. nov. also have keels on the metaventral spines in males – a secondary sexual character lacking in H. celata , and one which has not been previously reported in the genus. As well as being smaller than the new species, H. occidentalis has a more strongly evident greenish sheen, which is present over the entire dorsum with some metallic reflections, a narrower marginal elytral puncture field ( Fig. 9 ) and much closer larger punctures on the pronotum and elytra. H. celata celata is superficially more similar to the new species in colouration and size, but has a much longer metaventral spine ( Fig. 13 ). The aedeagi of the three species ( Figs 14–16 ) also differ significantly, that of H. perissinottoi sp. nov. being most similar to H. occidentalis , sharing the same general design. The two species differ in the angling of the parameres in ventral view, the more dorsally directed median lobe of H. perissinottoi sp. nov. in lateral view and the shape of the median lobe in ventral view (distinctly expanded before the apex in H. occidentalis ; almost straight in H. perissinottoi sp. nov.), as well as its ventral ornamentation, best seen in lateral and dorsolateral views – note in particular the ventral raised strip, which is relatively high in H. occidentalis , and much lower and less evident in H. perissinottoi sp. nov. ( Figs 14, 16 ).

Etymology. Named for Professor Renzo Perissinotto, coleopterist and aquatic biologist, whose work has significantly improved understanding of the biodiversity, ecology and conservation of the Lake St. Lucia system, and who kindly organised the 2015 sampling trip on which this species was detected. The specific epithet is a noun in the genitive case.

Distribution and ecology. Known to date only from small wetlands around Lake St. Lucia (e.g. Figs 2–3 ), where it appears to be widespread, at least locally. Here it was part of a diverse water beetle assemblage (see PERISSINOTTO et al. 2016), including Hydrochara fulvofemorata (Fairmaire, 1869) , itself not previously reported from South Africa ( SMETANA 1980, STALS 2007). Many more specimens of Hydrobiomorpha / Hydrochara were seen in the field than were collected, and the new species is likely to be common in this region. Found in both basin and depression wetlands (sensu OLLIS et al. 2013).

Figures

Figs 1–3. 1 – Hydrobiomorpha perissinottoi sp. nov., male holotype, dorsal habitus; 2–3 – Hydrobiomorpha habitats at iSimangaliso. 2 – Western Shores 1; 3 – False Bay 5.

Figs 4–7. Meso and metaventrites of Hydrobiomorpha perissinottoi sp. nov. 4, 6 – male paratype; 5, 7 – female paratype. 4–5 – ventral; 6–7 – lateral.

Figs 8–13. Hydrobiomorpha elytral margins and metaventral spines. 8–10 – elytral margins; 11–13 – metaventral spines. 8, 11 – Hydrobiomorpha perissinottoi sp. nov.; 9, 12 – H. occidentalis Balfour-Browne, 1939; 10, 13 – H. celata celata Mouchamps, 1959.

Figs 14–16. Aedeagi. 14 – Hydrobiomorpha perissinottoi sp. nov.; 15 – H. celata celata Mouchamps, 1959; 16 – H. occidentalis Balfour-Browne, 1939.