Hexanchorus angeli, Laššová, Kristína, Čiampor, Fedor & Čiamporová-Zaťovičová, Zuzana, 2014

Laššová, Kristína, Čiampor, Fedor & Čiamporová-Zaťovičová, Zuzana, 2014, Two new Larainae species from Guayana region, Venezuela (Coleoptera: Elmidae), Zootaxa 3753 (2), pp. 187-195 : 188-191

Hexanchorus angeli n. sp.

Figs 1–14

Type locality: environment of the Río Churun, large stream ca. 15 m wide and mostly about 0.5 m deep with orange-brown coloured humic water (specimens were collected at light).

Type material: holotype male ( NMW): ” Venezuela, Auyán Tepui env., Salto Angel camp, Río Churun env., at light, 506 m a.s.l., 05°58'35.5'' N, 062°30'58.1'' W, 5.12.2012 ”, paratypes ( CCB, MIZA, NMW, ZSM): 11 specimens with the same locality data as holotype.

Diagnosis. Hexanchorus angeli n. sp. is externally similar to all other known Hexanchorus species. It differs in combination of the following characters: 1) presence of a greenish iridescence on dorsal surface, 2) without median longitudinal sulcus at base of pronotum, 3) elytral apices feebly (males) or distinctly (females) upturned, 4) third ventrite of females with distinct median process, 5) ventrite 5 slightly emarginated apically in males, 6) aedeagus with median lobe short, narrow apically, parameres long abruptly constricted basally.

Description. Body elongate, subparallel ( Figs 1, 2 ); length 3.16 mm; width 1.15 mm; dorsum moderately convex, dorsal surface with very dense short recumbent setae with greenish iridescence and more sparse, longer, dark, semierected setae. Body black, scape and pedicel dark brown, maxillae, trochanters and basal portion of femora pale brown, tarsal claws reddish-brown. Venter dark with light yellowish-brown setae.

Head. Head partly retractable into prothorax. Labrum densely setose, with largely rounded anterior angles, feebly emarginate anteromedially; clypeus densely setose, shorter and narrower than labrum, about 3.0 times as wide as long, frontoclypeal suture visible, almost straight. Eyes well developed, suboval in lateral view, protruding from head outline, bordered with long black curved setae arising near dorsal and ventral side and extend toward middle of eye, cranial surface not raised around eyes. Frons between eyes flat. Antennae eleven segmented, densely setose, scape curved, about 2.0 times as long as pedicel, remaining segments about three times longer than scape and pedicel combined, segments 3–10 short, subtriangular, terminal segment subglobular with slightly pointed apex.

Thorax. Pronotum widest behind middle, PW: 0.88 mm, PL: 0.78 mm; partly shiny with dense smaller and larger setigerous punctures; disc convex, divided by broad transversal U-shaped depression in the first third; triangular median depression at base shallow, reaching basal third of pronotum. Sides of pronotum convex in posterior 2/3, slightly constricted before base, feebly convex in anterior third before transverse constriction; lateral margins narrowly rimmed, posterior angles orthogonal, anterior angles not produced. Lateral sides decliving to the ventral side. Hypomeron narrow, sinuate. Prosternal process narrow, triangular, with apex rounded; prosternum in front of coxae extremely narrow, reduced. Mesoventrite short and wide, disc narrowed posteriad, posteromedially with deep triangular impression for reception of prosternal process. Metaventrite wide, metaventral discrimen thin, present along basal 2/3; disc raised on sides, surface reticulate and densely setose ( Fig. 3 ). Elytra (EL: 2.42 mm, EW: 1.15 mm), in anterior 2/3 parallel, then tapering toward apices, disc moderately convex, sides strongly declivous; surface glabrous with very dense short setae with greenish iridescence and sparser longer semierect hairs; elytral margin only very narrowly rimmed; humeri rounded, slightly produced; epipleuron widest in anterior third, then reduced, very thin. Each elytron with ten rows of small punctures, striae impressed on disc, impression diminishes toward lateral margin and elytral apex. Scutellum wide, subtriangular, anterior portion flat, apical triangular part raised. Legs moderately long, mesotibia markedly flattened, longest.

Abdomen. Ventrites densely setose ( Fig. 3 ). Intercoxal process of first ventrite with apex rounded, lateral sides not raised, sublateral carinae absent; distal margins of first and second ventrite feebly sinuate; third ventrite simple in males, in females with distinct median process ( Fig. 12 ). Ventrite 5 with distal margin emarginated in males ( Fig. 7 ), simple in females ( Fig. 10 ). Sternite 8 weakly sclerotized and reduced as two darkened spots in males ( Fig. 8 ), deeply emarginate in females ( Fig. 11 ). The ninth segment and spiculum gastrale extremely elongate ( Fig. 6 ). Aedeagus ( Figs 4, 5 ) elongate, penis with fibula feebly sclerotized, better visible from lateral view, corona membranous; parameres slightly shorter than penis, in lateral view widest in middle, moderately narrowed in basal half, distal half moderately narrowed toward rounded apex, in ventral view moderately narrowed in apical ca. 0.4, in basal 0.6 parallel-sided, base constricted; penis in ventral view subparallel in basal 0.6 with distinct basal apophyses, apical 0.4 narrowed toward thin rounded apex, in lateral view slender, sinuate, with widened basal 2/3. Phallobase parallelsided, curved in lateral view. Penis and parameres with sparse fine spines. Ovipositor ( Fig. 9 ) with stylus (terminal segment) short, slightly widened basally; preterminal segment short and robust, about 2.7 times as long as stylus, apically with numerous curved blunt and acuminate spines or sensilla; basal segment with baculus membranous, ca. 0.8 times as long as preterminal and distal segments combined, baculus straight, well sclerotized.

Sexual dimorphism. Both sexes are generally similar in shape and size, however males are usually slightly smaller. From females, males can be easily distinguished by elytral apices not produced, by ventrite 3 without distal process, by shape of distal margin of ventrite 5, by ventrites 1–2 concave, not convex. Pronotum of males with feeble median triangular depression in basal third, medio basal portion of female pronotum without visible depression.

Distribution. Hexanchorus angeli n. sp. is known only from the type locality.

Remarks. One female of Hexanchorus was found also in Río Tarota (Gran Sabana), more than 120 km distant from the type locality of H. angeli n. sp. This female is morphologically very similar to the females of the species described herein. However, observed 4 % molecular distance, measured as uncorrected p-distance on 816bp long fragment of the mitochondrial gene for cytochrome oxidase c subunit I (tree not shown), suggest that the female from the Gran Sabana should belong to another species.

Habitat. The specimens were caught on light, so we can only suggest that H. angeli n. sp. adults live in and around rapids of the Río Churún, as do most of other related Larainae species, and their larvae develop in the same river or their tributaries. At the place of collecting, the river was about 15 m wide, relatively shallow. Substrate was formed by gravel with large stones and boulders weekly covered by periphyton ( Figs. 13, 14 ). Water was naturally humic, brown coloured.

Etymology. The species is named after Jimmie Angel, an American aviator who was the first man flying over the Angel falls. These waterfalls are the highest in the World, falling from the slopes of the Auyán tepui close to the type locality.

Figures

FIGURE 3. Hexanchorus angeli n. sp. male and female ventral view.

FIGURES 1, 2. Habitus of Hexanchorus angeli n. sp.: 1) holotype, male, 2) paratype female.

FIGURES 4 – 12. Hexanchorus angeli n. sp.: 4) aedeagus lateral view; 5) aedeagus ventral view; 6) male ninth segment and spiculum gastrale; 7) ventrite 5 male; 8) sternite 8 male; 9) ovipositor; 10) ventrite 5 female; 11) sternite 8 female; 12) ventrite 3 female. Scale bars: 0.1 mm.

FIGURES 13 – 16. Type localities: 13, 14) Río Churún, type locality of Hexanchorus angeli n. sp.; 15, 16) small stream near Cerro Autana, type locality of Hypsilara autanai n. sp.