Ancyronyx reticulatus, Kodada, Ján, Jäch, Manfred A. & Jr, Fedor Čiampor, 2014

Kodada, Ján, Jäch, Manfred A. & Jr, Fedor Čiampor, 2014, Ancyronyx reticulatus and A. pulcherrimus, two new riffle beetle species from Borneo, and discussion about elmid plastron structures (Coleoptera: Elmidae), Zootaxa 3760 (3), pp. 383-395 : 384-386

Ancyronyx reticulatus sp.n.

Type locality ( Fig. 29 ). Tributary of Kuamut river near Kampung Pisang Pisang (ca. 100 km E of Sapulut, along logging road Sapulut—Tawau), ca. 10 m wide, meandering, with large submerged logs; Sabah, Borneo, Malaysia. Type material. Holotype ♂ ( NMW): “ Malaysia, Sabah, (Borneo), Kuamut river env. near Kampung Pisang Pisang, 3.-4. VI. 1996, 14b: tributary of Kuamut river, ca 10m wide, with large submerged logs”. Paratypes ( CKB, NMW): 1 ♂ 2 ♀♀: same locality data as holotype, 1 ♀: “ Malaysia, Sabah, (Borneo), Kuamut river env. near Kampung Pisang Pisang, 3.-4. VI. 1996, 14a: shaded stream in primary forest with submerged wood”.

Description. Habitus as in Figs 1–2 . Body form suboval, elytra moderately convex dorsally. BL: 1.92–1.95 mm in ♂♂, 2.00– 2.10 mm in ♀♀; EW: 0.87–0.90 mm in ♂♂, 0.90–0.92 mm in ♀♀; BL/EW: 2.14–2.23 in ♂♂ and 2.22–2.27 in ♀♀.

Colouration pattern as in Figs 1–2 . Labrum brown on lateral thirds, yellowish on middle third; mouth parts and antennae yellowish, clypeus and frons yellowish, yellowish portion of frons triangularly narrowed posteriad, cranium black dorsally and posteriad of eyes; pronotum yellowish with large mesal black spot on anterior third; scutellum brownish; elytra black, medially with extensive, nearly X-shaped yellowish pattern, apices yellowish; venter yellowish except of dark brown mesanepisterna, metanepisterna, lateral portion of metaventrite and lateral portions of ventrites 3–5; coxae and femora yellow; tibiae black on proximal three fourths, yellowish on distal fourth; tarsomeres and claws yellowish.

Conspicuous cuticular microstructures are present on abdomen and anterolateral portion of pronotum (see discussion about plastron below, Figs 23–28 ). Genae, sides of prosternum, mes- and metepisterna, lateral portion of metaventrite, epipleura posteriorly to ventrite 4, lateral portions of ventrites, exposed portions of coxae and femora are irregularly covered with encrustations/secretions ( Figs 8, 10 , 17–18, 21–24 ).

Head. Labrum about as long as clypeus, anterior margin slightly concave, nearly straight; surface with dual punctation, larger punctures deeper with fine setae, smaller punctures very fine and shallow. Clypeus wide, densely punctate and finely reticulate. Frons and vertex finely punctate and granulate ( Fig. 6 ), granules elongate, distinct; surface between granules reticulate, reticulation more distinct on black portion of vertex; frontoclypeal suture nearly straight, finely impressed. Eyes moderately protruding. Antennae 11-segmented, slender, slightly shorter than pronotum. Gena microsculptured ( Fig. 9 ); gula narrow, smooth, gular sutures distinct; posterior tentorial pits deep ( Figs 8, 10 ). HW: 0.43–0.48 mm in ♂♂, 0.45–0.48 mm in ♀♀; ID: 0.23–0.25 mm in ♂♂, 0.25 mm in ♀♀.

Thorax. Pronotum distinctly wider than long (PL/MW: 0.74 in ♂♂, 0.75–0.79 in ♀♀), widest near posterior angles; anteriorly attenuate, anterior margin strongly arcuate; lateral pronotal carina absent, hypomeral portion visible in dorsal view; anterior transverse groove distinctly impressed, oblique and dividing pronotum, area posteriad of transverse groove strongly gibbous on each side of disc; anterior mesal longitudinal carina distinct; posterolateral oblique grooves well impressed. Pronotal surface ( Figs 5, 7 ) densely punctate, reticulate anteriorly, interstices smooth on disc and posteriorly; punctures deeply impressed, irregular in shape, distinctly larger than diameter of a facet, nearly confluent, denser on disc and anteriorly than in posterolateral portion; PL: 0.58 mm in ♂♂, 0.60–0.67 mm in ♀♀, MW: 0.78 mm in ♂♂, 0.80–0.85 mm in ♀♀. Prosternum irregularly, densely and roughly punctate and reticulate, very short in front of procoxae ( Figs 10–12 ); prosternal process distinctly transverse, medially impressed, posterior margin widely rounded, feebly protruding posteriad. Scutellum nearly pentagonal, smooth and shiny ( Fig. 15 ). Elytra elongate, EL: 1.40 mm in ♂♂, 1.43 mm in ♀♀, EL/EW: 1.55–1.60 in ♂♂, 1.54–1.58 in ♀♀, slightly tapering posteriad from ca. 0.1–0.7, then convergent to conjointly rounded apices; with ten more or less regular rows of punctures ( Fig. 15 ), seven rows between suture and shoulder, 3–6 punctures in irregular accessory scutellary rows; punctures large, round and deeply impressed on disc, smaller and less distinct anteriorly; interstices and intervals wider and flat on disc, narrower and feebly convex laterally and posteriorly, surface finely reticulate (matt) bearing shiny rounded granules ( Fig. 16 ); humeri prominent. Mesoventrite ( Figs 11, 13 ) nearly flat, approximately half as long as prosternum along midline, mesoventral cavity shallow and narrow, surface irregularly punctate and reticulate, mesoventral discrimen fine. Metaventrite ( Fig. 13 ) about as long as prosternum and mesoventrite combined, disc with shallow longitudinal depression mesally, discrimen raised ( Fig. 14 ); surface punctate, granulate and entirely reticulate, punctures laterally coarser and denser than on disc. Hind wings not examined. Forelegs about 1.4 times as long as body; pro- and mesocoxae large and prominent, bluntly drop-shaped; metacoxae smaller and less protruding laterally; femora ( Figs 17–18 ), tibiae, and tarsi with short setae, tibiae with a few additional longer setae; distal tarsal segments with several longer setae near apex; claws well developed, base with three teeth, basal one very small and hardly discernible ( Fig. 19 ).

Abdomen. Abdominal intercoxal process moderately longer than length of ventrite 1 posterior of metacoxae, very wide, arcuate anteriorly ( Fig. 20 ); ventrite 1 longest, ventrite 2 ca. 0.7 times as long as ventrite 1, ventrite 3 ca. 0.7 times as long as ventrite 2, ventrite 4 ca. 0.8 times as long as ventrite 3, ventrite 5 ca. as long as combined length of ventrites 3 and 4. Surface of ventrites with large punctures and setigerous, flat, smooth, more or less cordiform granules ( Figs 21, 22 , 27 ); punctures more distinct and nearly confluent on mesal portion, granules more prominent and more conspicuous laterally, ventrite 5 granulate.

Male sternite IX ca. 400 Μm long; apical margin distinctly emarginate, lateroapically with microsetae and cluster of pores; paraprocts not reaching beyond apical margin. Tergite VIII in both sexes finely reticulate, with conspicuous median transverse ridge separating posterior and anterior portion; basal half with microtrichial pattern; apical margin hyaline, subapical fringe of hair-like setae present, setae on sublateral portions stronger and longer than those along margin.

Aedeagus ( Figs 31, 32 , 34) ca. 410 Μm long; penis about 2.0 times as long as phallobase, sides subparallel along basal half, gradually tapering apicad, subapically distinctly curved ventrad (lateral view), dorsolateral portion with only a few very short, indistinct setae, lateral basal apophyses moderately long and slender; ventral sac large, fibula conspicuous, wide; surface of endophallus without spinules, corona well developed. Phallobase asymmetrical; parameres almost reaching apex of penis, widest near base, narrowest near middle, dorsal margin strongly sinuous, ventral margin nearly straight, apex wide (all in lateral view); mesal and outer surface of parameres with spinules arranged in short longitudinal rows.

Ovipositor (Fig. 39) ca. 405 Μm long; stylus slender, outer margin slightly bent outwards, inner margin nearly straight (dorsal view). Coxite short and stout, posterolateral angle rounded, not protruding, distal portion ca. 1.1 times as long as wide, with several rather short and wide, peg-like setae; inner margin moderately pubescent; basal portion approximately as long as distal portion, with peg-like and hair-like setae, most setae set laterally. Valvifer longer than coxite, apical margin with hair-like setae.

Sexual dimorphism. Females are longer and, on average, wider than males. The longitudinal depression of the metaventrite is narrower and shallower in females. Ventrite 5 longer and narrower in females; anterior median strut of sternite VIII longer in females.

Differential diagnosis. This species is similar to A. helgeschneideri (see Figs 3 , 33, 35) from the Philippines. The latter differs from the new species in: 1) smaller size; 2) presence of dark spot on femora; 3) pronotum with black or brown spot posteriad of anterior transverse groove; 4) black genae; 5) pronotal gibbosities narrower and more pronounced; 6) parameres longer and narrower; 7) apex of parameres continuously narrowed; 8) distal portion of coxite of ovipositor ca. 1.5 times as long as wide (see Freitag & Jäch 2007).

Variability. Specimens examined show slight variability in the size of the X-shaped yellowish pattern on the elytra and in the intensity and size of black spots on the ventrites. In one of the two males tarsomeres 1–3 are light brown.

Distribution. This species is known only from two localities in Sabah ( Figs 29, 30 ).

Ecological Notes. At the type locality four specimens were collected from a large trunk of waterlogged wood together with Ancyronyx acaroides , A. procerus and A. sarawacensis . Some species of Graphelmis Delève, 1968 (Elmidae) , Elmomorphus Sharp, 1888 and Stenomystax Kodada, Jäch & Čiampor, 2003 (Dryopidae) also occurred in the same habitat. The single specimen from the second site was found on a smaller branch of submerged wood in a shaded small stream not far from the type locality co-occurring with Graphelmis spp.

Etymology. Adjective, reticulatus (Latin) —reticulate. Named in reference to the reticulate elytral surface.

Figures

FIGURES 29 – 30. Habitats of Ancyronyx reticulatus: 29) type locality, tributary of Kuamut river near Kampung Pisang Pisang; 30) shaded stream in primary forest, tributary of Kuamut river.

FIGURES 1 – 4. Dorsal habitus of 1) Ancyronyx reticulatus, male, holotype; 2) A. reticulatus, female, paratype; 3) A. helgeschneideri, male, paratype; 4) A. pulcherrimus, male, paratype. Scale bar 0.5 mm.

FIGURES 23 – 28. Ancyronyx reticulatus, female: 23) head, pronotum and fore leg with secretions / encrustations on coxa, femur, anterolateral portion of pronotum and near base of mandible, lateral view; 24) enlarged view of area indicated on previous figure showing dense plastron microstructures in cracks of encrustations / secretions (black arrows); 25) base of hind leg, ventrite 1 and part of epipleuron and elytron, lateral view; 26) enlarged view of area indicated on previous figure showing presumed plastron structures, El: elytron, EP: epipleuron, V 1: anterolateral portion of ventrite 1; 27) enlarged surface showing dense cuticular microstructures and shiny granules with setae; 28) cuticular microstructures on anterolateral portion of ventrite 2.

FIGURES 5 – 13. Ancyronyx reticulatus, female: 5) head and pronotum, dorsolateral view; 6) reticulate surface and elongate granules on head, dorsolateral view; 7) pronotum, detail of reticulate and punctate surface on anterior portion, dorsolateral view; 8) head and anterior portion of prothorax, showing gular sutures, ventrolateral view; 9) enlarged view of area indicated on previous figure showing cuticular sculpture on gena possibly associated with plastron; 10) head, prothorax, procoxa and part of mesoventrite, ventral view; 11) prosternum, mesoventrite and part of metaventrite, ventral view; 12) prosternal sculpture with more or less cordiform granules and irregular deep punctures, ventral view; 13) thorax and anterior ventrites, ventral view.

FIGURES 14 – 22. Ancyronyx reticulatus, female: 14) posteromesal portion of metaventrite with discrimen, surface finely reticulate, ventral view; 15) anterior portion of right elytron and scutellum, dorsal view; 16) elytral sculpture with microreticulation; shiny granules (setae abraded) and puncture, dorsal view; 17) metafemur, dorsal view; 18) femoral microsculptures, dorsal view; 19) hind claws, ventrolateral view; 20) ventrites 1 – 3, ventral view; 21) lateral portions of ventrites 1 – 2 showing deep large punctures, cordiform setose granules and secretions / encrustations, ventrolateral view; 22) enlarged view of area indicated on previous figure.

FIGURES 31 – 32, 34. Ancyronyx reticulatus: 31) aedeagus with endophallus extruded, dorsal view; 32) aedeagus, lateral view; 34) same, ventral view. FIGURES 33, 35. A. helgeschneideri: 33) aedeagus, lateral view; 35) same, ventral view. Scale bar 0.1 mm.