Okalia necopinata, Kodada & Jäch & Selnekovič & Goffová, 2022

Kodada, Jan, Jaech, Manfred A., Selnekovic, David & Goffova, Katarina, 2022, Okalia necopinata sp. nov. (Insecta, Coleoptera, Elmidae) from Gunung Mulu National Park in Sarawak (Malaysia), ZooKeys 1092, pp. 79-92 : 79

Okalia necopinata sp. nov.

Figs 2A , 3A-F , 4A, B , 5A, E, F , 6

Diagnosis (all specimens examined are wingless).

Length: 1.44-1.63 mm, width: 0.78-0.88 mm. Body widely obovate and strongly convex dorsally. Surface scarcely finely punctate, smooth; dorsal plastron on head, anterolateral portion of pronotum, and elytra between lateral margin and fifth interval. Pronotal median groove absent, sublateral carinae very fine, indistinct; femora moderately expanded; fifth elytral interval granulate on posterior half, sixth near apex, seventh entirely; elytral striae obsolete; elytral apices obliquely truncate; lateral sides of pronotum and elytra serrate. Penis apically arrowhead-shaped (in ventral/dorsal view). Ovipositor: coxite long and narrow; posterolateral angle strongly produced laterad, acute. Female internal genital tract with bursa copulatrix enlarged, saccular, as long as ovipositor, with a pair of mesal longitudinal sclerites, a pair of admedian densely denticulate sclerites, and with numerous short spinules, especially laterally; spermatheca with two branches.

The new species differs from Okalia globosa in the larger size, longer elytral declivity, and especially in the granulation of the fifth elytral interval being confined to the posterior half. Furthermore, the elytral and pronotal punctation is less distinct than in O. globosa . The arrowhead-shaped apex of the aedeagus is more elongate, and the apex of the coxite of the ovipositor is more strongly produced laterad and more acute.

Furthermore, the single available female from Sabah differs in the more extensive granulation of the fifth elytral interval, and the irregular microscopic wrinkles of the elytral intervals. This winged female has also a narrower and longer pronotum with lateral sides subparallel posteriorly, and the sublateral pronotal carinae are more prominent than in the new species.

Etymology.

The epithet, a Latin adjective (necopinata = unexpected, unforeseen), refers to the unexpected discovery of this species in a small, very slowly flowing stream, a somewhat atypical habitat for riffle beetles.

Type locality.

Very shallow, slowly flowing, meandering stream (Fig. 6 ), which is entirely shaded by the trees of a primary dipterocarp forest in the limestone area of Gunung Mulu National Park, ca 4°02'59.5"N, 114°49'24.3"E, 70 m a.s.l. (north-eastern Sarawak, Borneo, Malaysia). The stream is ca 1 m wide, with a few deeper pools, and contains large amounts of accumulated leaves; the bottom is sandy with fine gravel and wood debris; the muddy banks are densely covered with Phymatarum borneense . [Note. Unfortunately, Kodada et al. (2020a, 2020b) provided incorrect coordinates for this locality for Ancyronyx pulcherrimus Kodada, Jäch, Čiampor and A. sarawacensis Jäch].

Material examined.

Holotype ♂ (CFDS): " Malaysia, Sarawak, Marudi distr. , Gunung Mulu NP, 12.10.2018, (40) 4°02'59.5"N, 114°49'24.3"E, 70 m a.s.l., small stream in primary forest, Kodada & Selnekovič lgt." . Paratypes including sequenced voucher specimens (CFDS, CKB, NMW): 5 ♂♂, 10 ♀♀ and 7 specimens (sex not examined) with same collecting data as holotype .

Description of holotype.

Habitus (Fig. 2A ). Body form widely obovate, widest at elytral midlength, lacking shoulders (Fig. 3A ); body 1.81 × as long as wide (BL/EW); BL: 1.49 mm, EW: 0.82 mm. Plastron structures on clypeus, frons, area posteriad of eyes, anterolateral portion of pronotum, hypomera, lateral portions of prosternum, mesepisterna, metepisterna, lateral portion of metaventrite, epipleura, lateral portions of ventrites, elytra between margin and fifth interval, anterior face of metacoxae, femora and tibiae.

Head. Partly retractable, retracted portion reticulated, without plastron structures; head width 0.31 mm; interocular distance 1.4 × as long as longitudinal diameter of eye. Labrum wider than long, anterior margin with row of shorter trichoid setae ventrally, anterolateral portion with row of longer setae, posterior portion microreticulate. Clypeus about as long as labrum, wider than long; frontoclypeal suture distinct, arcuate; surface finely punctate, punctures setigerous, setae adpressed. Frons with setigerous micropunctures and scattered pointed granules; granules half as wide as a facete diameter, separated by distances of about 1.5-3.0 × a facete diameter. Eyes small, feebly protuberant in dorsal view, ellipsoidal in lateral view, longer than wide, with about 50 facets (Fig. 3B ). Subantennal groove very shallow, confined to anteroventral portion of eye. Antenna short, reaching posterior margin of eye, eight-segmented, capitate; scape short; pedicel longer, enlarged distally, with a few trichoid setae; segment 3 shorter than pedicel; segments 4-7 short, wider than long; segment 8 nearly as long as combined length of five preceding segments, enlarged, with numerous setae.

Thorax. Pronotum slightly wider than long, widest near posterior fourth, PW: 0.54 mm, PL: 0.46 mm; disc strongly convex, sparsely, and finely punctate; punctures with moderately long semi-erect setae, distinctly smaller than facets, and separated by distances 1.5-3.0 × of a facete diameter. Sublateral carinae indistinct, present on posterior fifth of pronotum; median groove absent; prebasal pits shallow; anterior margin translucent, moderately arcuate; anterior angles acute and strongly protruding; posterior angles with fine wrinkles; lateral margin serrate, more strongly along anterior than along posterior half. Plastron area nearly triangular, on each side of midline, widest anteriorly, reaching nearly midlength. Hypomeron broadest near middle, separated by a gap from prosternum anteriorly, postcoxal projection absent. Prosternum in front of coxae about as long as prosternal process, feebly deflected anteriad; prosternal process subtriangular, narrowed posteriad, with apex feebly rounded, nearly truncate, sides weakly and widely raised. Procoxae subglobular, separated near middle by distance of about 0.5 × of head width (Fig. 3D ); mesocoxae subglobular, more transverse than procoxae, intercoxal distance near middle twice as long as in procoxae; metacoxae about twice as wide as long, reaching elytra, separated by same distance as mesocoxae; pro- and mesocoxal cavities deep; paired mesoventral procoxal rest deep, strongly oblique. Mesothorax short, strongly sclerotized ventrally and dorsally; scutellum small, subtriangular; mesoventrite short, about twice as long as wide (Fig. 3E ), medial groove deep and narrow; mesepisterna fused with metaventrite; mesepimeron short, strongly sclerotized; mesoventral process with lateral sides raised. Metaventrite ca 1.5 × as long as mesoventrite, slightly depressed on disc; mesometaventral junction formed by distinct angulated suture; discrimen fine; transverse suture absent, its position marked by row of larger punctures; exposed portion of metepisternum long and very narrow; metaventral process wide, with lateral sides raised; surface of disc very finely punctate, punctures distinctly smaller than a facete diameter, widely separated. Elytra strongly convex dorsally, highest near anterior third (lateral view), obovate; EL: 1.04 mm, EW: 0.82 mm; apices more or less obliquely truncate; lateral sides and apices serrate. Striae obsolete, their punctures very fine, slightly larger than punctures of intervals; surface with semi-erect, moderately long trichoid setae on striae and intervals, and with a few scattered longer and thinner setae on plastron area. Interval 5 with a dense row of granules along posterior half (Fig. 3C ); sixth interval with a few scattered granules anteriorly, densely granulate near apex; seventh interval granulate along entire length; shoulders absent. Epipleura widest anteriorly, inflected and slightly narrowed at level of metacoxa, concealed by lateral projection of ventrites 3 and 4, effaced at truncate apical portion. Legs shorter than elytra and pronotum combined, surface granulate and setose. Femora nearly as long as pronotum, moderately expanded and feebly grooved distally; mesofemur shorter than pro- and metafemur; pro- and mesofemur with dense adpressed long setae in proximal half on face adjacent to body. Tibiae subequal in length with femora, straight and simple. Tarsi five-segmented, shorter than tibia, reticulate; terminal tarsomere nearly as long as combined length of preceding segments; segments 1-4 with a few peg-like stout setae ventrally and with a few trichoid setae laterally and dorsally; terminal segment with trichoid setae only. Claws shorter than half of terminal segments, moderately curved, similar in form and inclination angle; empodium with two short setae.

Abdomen. Ventrites strongly sclerotized, moderately convex, separated by sutures; lateral margins of ventrites 1-2 evenly arched, in ventrites 3-4 projecting laterad (Fig. 3F ), in ventrite 5 with fine denticles. Abdominal intercoxal process wide and short, ca 3.0 × as wide as long; anterior portion with irregular fine longitudinal furrows; admedian carinae of ventrite 1 absent; ventrite 5 with numerous irregularly spaced granules, posterior margin narrowly truncate, with one pair of lateral clusters of stronger setae. Aedeagus (Fig. 4A, B ) ca 0.70 mm long, bent and strongly sclerotized, tubular, without parameres, subapically abruptly constricted to form arrowhead-like apex (ventral/dorsal view); ventral sac present in posterior portion of aedeagus, lacking corona, bearing two longitudinal lateral sclerotizations; endophallus with numerous small spinules; phallobase short, its anterior portion strongly asymmetrical.

Female genitalia. Ovipositor (Fig. 5A ), ca 0.53 mm long, as long as combined length of ventrites 3-5; vulva between base of coxites. Transverse baculum well sclerotized, longitudinal baculum ca 1.1 × as long as coxite (measured from the apical margin of coxite to point where it is joining the transverse baculum). Coxite long and narrow, divided by transverse line ventrally, apicolateral angle strongly produced laterad, acute (Fig. 5F ); distal portion ca. 1.8 × as long as proximal portion; stylus short, curved, with apical sensilla. Female internal genital tract: vagina elongate, simple; bursa copulatrix enlarged, saccular, as long as ovipositor, with a pair of mesal longitudinal sclerites, a pair of admedian, densely denticulate sclerites, and numerous short spinules, especially laterally; spermatheca with two branches, like those of O. globosa (Fig. 5D, E ).

Secondary sexual dimorphism.

Females are on average slightly longer and broader than males. No other prominent secondary sexual characters were found.

Variability.

The examined specimens vary moderately in punctation of pronotum and elytra as well as in size: BL ♂♂: 1.44-1.46 mm, ♀♀: 1.52-1.63 mm; EW ♂♂: 0.78-0.80 mm, ♀♀: 0.82-0.86 mm; PW ♂♂: 0.52-0.53 mm, ♀♀: 0.53-057 mm, PL ♂♂: 0.48-0.49 mm, ♀♀: 0.47-0.50 mm; EL ♂♂: 0.97-0.99 mm, ♀♀: 1.05-1.11 mm.

Distribution.

The species is so far known only from the type locality in Sarawak.

Figures

Figure 2. Habitus of Okalia species A O. necopinata sp. nov., wingless male, holotype, body length 1.49 mm B O. globosa Kodada & Ciampor, wingless male, paratype, body length 1.38 mm.

Figure 3. Okalia necopinata sp. nov., scanning electron micrographs A habitus, dorsal aspect B head and pronotum, dorsal aspect C elytra, dorsal aspect D habitus, ventral aspect E head and thorax, ventral aspect F abdomen, ventral aspect.

Figure 4. Aedeagi A Okalia necopinata sp. nov., holotype, dorsal aspect B same, lateral aspect C O. globosa Kodada & Ciampor, paratype, dorsal aspect D same, lateral aspect. Scale bar: 0.1 mm.

Figure 5. Female genitalia A Okalia necopinata sp. nov., ovipositor with bursa copulatrix and sternite VIII, paratype, ventral aspect B O. globosa Kodada & Ciampor, ovipositor with bursa copulatrix, paratype, ventral aspect C same, coxite and gonostylus, enlarged D O. globosa, spermatheca E O. necopinata, spermatheca F same, coxite and gonostylus, enlarged. Scale bar: 0.1 mm.

Figure 6. Stream in primary forest of Gunung Mulu National Park, Sarawak, type locality of Okalia necopinata sp. nov.