Ochthebius capicola ( Péringuey, 1892 )

Bilton, David T., 2021, Differentiation of South African coastal rock pool Ochthebius is associated with major ocean currents (Coleoptera: Hydraenidae), Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 61 (1), pp. 253-260 : 254-257

Ochthebius capicola ( Péringuey, 1892)

( Figs 1A,C , 2A,C )

Hydraena capicola Péringuey, 1892: 106 .

Ochthebius capicola : ൽ’OඋർΗඒආඈඇඍ (1933): 411 (new combination); Pൾඋĸංඇඌ & Bൺඅൿඈඎඋ Bඋඈඐඇൾ (1994): 151 (partim) (lectotype de- signation).

Material examined. SOUTH AFRICA: Wൾඌඍൾඋඇ Cൺඉൾ Pඋඈඏ.: 6 JJ

7 ♀♀ ( CDTB) ‘ 19/ix/2008 South Africa WC/ Boulders Beach, Simons/ Town, rock pools D T Bilton leg.’; 5 JJ 5♀♀ ( CDTB) ‘ 22/ix/2014 South Africa WC/ Yzerfontein beach/ rock pools D T Bilton leg.’; 9 JJ 9 ♀♀ ( AMGS, CDTB, NHMW, NMPC, SAMC) ‘ 23/ix/2019 South Africa WC/ Yzerfontein beach/ rock pools D T Bilton leg.’; 62 spec. ( NHMUK) ‘S. AFRICA:/ Cape Town,/ Sea Point,/ 27.iii.1954.// in rock-pools of/ splashzone// J. Balfour-Browne/ Brit. Mus. 1954-797// Ochthebius / capicola/ (Peringuey)/ Det. P. D. Perkins’; 1 J ‘ South Africa, Western Cape / Cape Town, Sea Point,/ A. Skale, 05.06.2001 ’.

Redescription. Size: JJ BL 1.95–2.35 mm; EL 1.30–1.35 mm; EW 0.85–1.00 mm. ♀♀ BL 2.05–2.95 mm; EL 1.30–1.50 mm; EW 0.95–1.05 mm.

Colour: Dorsum ( Fig. 1A ) brown to blackish, with greenish to coppery aeneous reflections, these sometimes covering most of upper surface with exception of lateral margins of pronotum, exposed mandible margins and labral apex, these areas being paler. Legs testaceous to brown; maxillary palpi and basal antennomeres yellow to pale testaceous, club segments darker. Venter piceous; palpifer and pronotal hypomeron paler.

Head: Labrum slightly transverse, broadly rounded laterally with straight to weakly emarginate, slightly thickened and raised apical margin; sides and apex minutely serrate. Surface of labrum dull, microreticulate, meshes isodiametric to slightly transverse; with sparse-moderate, medium punctures, bearing white, decumbent setae. Frontoclypeal suture distinct, arcuate, becoming weaker laterally. Clypeus, frons and vertex somewhat dull with aeneous reflections; with somewhat rugulose microreticulation of mostly isodiametric meshes and sparse-moderate, medium punctures bearing long, white, decumbent setae; reticulation especially strong on frons and vertex, becoming transverse on posterior vertex and occiput, here absent centrally. Interocular foveae shallow, relatively small, but abrupt. Ocelli obsolete, shining, reduced to patches approx. 2–4 reticulation meshes in size and not distinctly raised. Compound eyes moderately sized, occupying approx. 0.4 side of head, 8–10 ommatidia in longest series.

Pronotum: Widest just behind anterior angles, then gradually attenuate to posterior angles ( Fig. 2A ). Anterior margin broadly but very shallowly arcuate over median 0.6; posterior margin rounded; lateral margins straight behind widest point, anteriorly arcuate to anterior angles. Anterior and posterior angles obtusely rounded, the latter more so. Anterior and posterior margins with broad hyaline border; lateral margins with narrower hyaline border from just behind widest point to posterior angles, becoming broader posteriorly and continuous with hyaline edge of posterior margin. Surface weakly shining, with aeneous reflection, especially on disc; disc close to anterior and posterior margins strongly and subrugulosely microreticulate, where distinct isodiametric meshes are visible; elsewhere microreticulation highly rugulose, surface appearing micropunctate, with confluent, typically aeneous, raised areas between non-shiny depressions; entire surface with sparse, fine punctures bearing long, white, recumbent to decumbent setae. Irregular row of larger punctures, bearing long, white suberect setae along anterior margin each side of median emargination. Disc with very shallow, almost obsolete transverse impressions in front of and behind middle. Lateral depressions shallow, broad, expanded anterolaterally and nearly reaching anterior angles; shallowly, subrugosely punctate; microreticulation meshes not visible here. Lateral depressions and adjacent lateral areas of pronotum corrugated, with short transverse and somewhat longer longitudinal, shiny ridges between punctures.

Elytra: Elongate oval, broadest anteriorly; almost subparallel over anteromedian 0.3, then weakly attenuated to separately rounded hind angles. Anterior angles broadly rounded; shoulders distinct. Lateral margins very narrowly explanate. Elytral punctures ( Fig. 2C ) random, no trace of longitudinal series. Punctures close, coarse and deep anteriorly, almost confluent on disc behind shoulder; shallower posteriorly; all bearing long, white, recumbent setae. Interstices subrugulose, with open microreticulation of large, deeply impressed meshes, often reduced to transverse channels; more shining than head and pronotum, with aeneous reflection.

Legs: Elongate, slender, metatibial length slightly less than pronotal width. Protarsomeres 1–2 slightly widened and with pad of suction setae.

Venter: Mentum, submentum, and genae shining, microreticulation restricted to transverse ridges on outer areas of genae; mentum and submentum with sparse, fine punctures, bearing fine, white decumbent setae. Gula with dense, fine to medium punctures bearing short recumbent setae; surface shining between punctures, but overall appearance at low magnification dull. Antennal pockets well developed. Prosternum rugosely microreticulate and punctate, punctures bearing long, erect to recumbent setae which form part of the hydrofuge vestiture; mesoventrite same, but reticulation and punctures less impressed and dense, and vestiture sparser. Pronotal hypomeron broad, wet hypomeron shining, glabrous; hypomeral antennal pocket well developed. Elytral epipleurs broad anteriorly, narrowing gradually to ca. 0.2 from apex; surface shining, with sparse, scattered setae and narrow strip of hydrofuge vestiture interiorly over anterior 0.3; row of short, curved setae running along edge of narrow posterior 0.2. Metaventrite with isodiametric to transverse microreticulation, stronger at sides, somewhat obsolete in centre; with dense, fine punctures bearing shaggy hydrofuge vestiture; vestiture denser laterally, sparse and often rubbed off in central area. Abdominal ventrites 1–5 completely and 6 laterally with slightly transverse, rugulose microreticulation and densely hydrofuge pubescent; ventrite 6 medially sparsely pubescent over apical 0.6, shining; apical 0.5 of glabrous area entirely devoid of microreticulation, punctures and vestiture, strongly shining.Apical tergum sharply rounded, with tuft of long flagelliform setae on each side and few spiniform setae.

Aedeagus: Elongate ( Fig. 1C ), main piece curved in lateral view, particularly towards the apex; strongly curving to the right in ventral view. Apex of main piece relatively acute, rapidly attenuated, particularly in ventral view. Distal lobe narrow, elongate, sinuous. Parameres inserted close to base; elongate, narrow, curved as main piece in lateral view; apices slightly expanded, somewhat truncate in ventral view.

Female: Differs from the male in the following characters: labral margin not so strongly raised; lateral setae of mandibles smaller; explanate elytral margin broader; elytral apices conjointly rounded, but sutural margin emarginate just before apices (making apices appear slightly pointed); median 0.3 of ventrite 1 reduced to narrow, membranous strip, sternum on each side appearing somewhat triangular; apical tergum more angulately rounded, long setae curling away from midline and spiniform setae slightly more numerous; protarsomeres narrower, without suction setae; many specimens examined with elytra somewhat paler than in males.

Variation. In addition to small variations in size, specimens vary in colouration, some being paler than the individual illustrated, particularly on the elytra. There is also some variation in the density of the elytral punctation, some specimens from False Bay (Boulders Beach) having slightly sparser punctures on the disc than others and those from the West Coast. The aedeagus shows little variation in size and overall appearance, but some individuals examined have shorter distal lobes than illustrated, this variation being observed amongst specimens collected from the same pool. Differential diagnosis. Both this species and O. mlamboi sp. nov. are distinguished from O. rubripes by their random elytral punctation, equally microreticulate head and pronotum, the proportionally smaller elytra, smaller body sizes, and the aedeagi (see Pൾඋĸංඇඌ & Bൺඅൿඈඎඋ-Bඋඈඐඇൾ 1994). For separation of O. capicola from O. mlamboi sp. nov., see under the latter species below.

Comments. The type material (SAMC) consists of two damaged female specimens from Cape Town, which were designated as Lectotype and Paralectotype respectively by Pൾඋĸංඇඌ & Bൺඅൿඈඎඋ-Bඋඈඐඇൾ (1994). These were not available for re-examination, but topotypic specimens all belong to the taxon as interpreted here. Details of Richtersveld specimens (3 spec.) were communicated by P. D. Perkins, who confirmed that they matched O. capicola s. str. on both external sculpture and aedeagal characters.

Distribution and ecology. As newly defined, this species is largely restricted to the west coast of South Africa, from the Cape Peninsula in the south to the Namibian border (Richtersveld) in the north ( Fig. 3 ). It also occurs on the western shore of False Bay at Boulders Beach. The precise respective geographical limits of O. capicola and O. mlamboi sp. nov. in the Western Cape remain unclear, but like a number of other coastal taxa, this seems likely to be situated in False Bay (see Discussion). In all localities, the species is characteristic of supralittoral rock pools, typically occurring in small, typically eutrophic and highly anoxic pools in the splash zone on rocky coastlines. Adults and presumed larvae are, like most rock pool Ochthebius , often observed together grazing biofilms. Clusters of laboulbenial fungi of the genus Hydrophilomyces Thaxter, 1908 have been observed on the posterior central metaventrite of specimens from Yzerfontein; a different, unidentified laboulbenial genus being present on the prosternum of some of the same beetles.

Figures

Fig. 1. Ochthebius species. A – O. capicola (Péringuey, 1892) (Yzerfontein, Western Cape Province), male habitus; B – O. mlamboi sp. nov., holotype habitus; C – O. capicola (Péringuey, 1892) (Yzerfontein, Western Cape Province), aedeagus, lateral and ventral views; D – O. mlamboi sp. nov., holotype aedeagus, lateral and ventral views. Scale bar A–B = 1 mm; C–D = 0.25 mm.

Fig. 2. Ochthebius species, showing dorsal sculpture A & C – O. capicola (Péringuey, 1892) (Yzerfontein, Western Cape Province); B & D – O. mlamboi sp. nov. A & B – pronota; C & D – elytra. Scale bars = 0.5 mm.

Fig. 3. Distribution of material examined, with approximate positions of major ocean currents. Red symbol – O. capicola (Péringuey, 1892); blue symbol – O. mlamboi sp. nov.