Oxytrechus chioriae, Quéinnec & Ollivier, 2019

Quéinnec, Eric & Ollivier, Eric, 2019, Two new Oxytrechus species from Ecuadorian páramo (Coleoptera, Carabidae, Trechinae), Zootaxa 4646 (1), pp. 55-66 : 58-61

(a) Oxytrechus chioriae n. sp.

( Figs. 2 , 3 )

Type locality: Ecuador, Chimborazo volcano (Chimborazo Province), North-East side, around 4400 m.

Type series: Male holotype labelled: „ Ecuador, Chimborazo Province, Chimborazo volcano, north-eastern slope, Portal Andino, Polylepis sp. grove , alt. 4400 m, 1°27’37’’S 78°46’15’’W, 28.VII.2018, E. Quéinnec & R. Chiori leg.“ (white label, p) / „Holotype Oxytrechus chioriae sp. nov. Quéinnec & Ollivier des.“ (red label, p), in CEQ; Paratypes: 1 Male, 1 Female, same data as for the holotype, but labelled: „ Paratype Oxytrechus chioriae sp. nov. Quéinnec & Ollivier des. “ (red label, p) in MNHN, CEO .

Diagnosis. Externally similar to O. mateui Allegro, Giachino & Sciaky, 2008 from Atacazo volcano due to the general shape of the body but easily recognized at first sight on its smaller size: 3.0– 3.1 mm (instead of 3.31–3.51 mm in O. mateui ). However, it differs markedly by the shape of the aedeagal median lobe and the structure of the endophallus. Also, very similar to O. guaguanus Mateu, 1991 , from Guagua Pichincha volcano, by the aedeagal shape but, in lateral view, the median lobe is more convex in the middle, less elongated and thick, more narrowed towards apex; with a helicoidal-shaped endophallic copulatory piece and with an extensive sclerotinization of its anterior portion. Though similar to each other at first sight, the three species differ in many details of external morphology and besides, quite different in conformation of the male genitalia.

Description. A medium-sized Oxytrechus species (LT = 3.0– 3.1 mm). Head, pronotum and elytra blackish brown, markedly shiny; elytra slightly iridescent. Clypeus, labrum, palpi, antenna and legs bright reddish brown. Apterous.

Head subquadrate (HW/HL = 0.55/0.55 = 1 in male holotype, and in average), large, transverse, with deep frontal furrows not angulate at the middle and widely divergent posteriad; frons and supraorbital areas moderately convex, bearing a foveola at the root of each supraorbital seta; two pairs of supraorbital setae lying on lines diverging backwards; eyes small but fairly protruding, more or less longer than genae, which are gently convex and completely glabrous; neck very wide, with constriction distinct; labrum transverse, with the apical margin shallowly but widely emarginate; mandible short, stout, feebly arcuate in apical third and obtusely tridentate; antennae short and fairly stout, reaching basal third of the elytra, scape thick, shorter but broader than terminal segment, segments 2 and 4–10 subequal in length, each subcylindrical and fully twice as long as large, segment 3 slightly longer than the neighboring ones and about five-sevenths as long as the terminal, which is the longest.

Prothorax. Pronotum cordate, wider than head, strongly transverse (PW/PL = 0.75/0.55 = 1.36 in male holotype; 1.35 in average), widest at about five-sevenths from base, and more gradually but strongly contracted towards base than towards apex, with the sides narrowly but entirely bordered; sides strongly rounded near the widest part, rather gently so behind middle and briefly sinuate just a little before basal angles; front angles not projecting forwards; base strongly arcuate, with hind angles very obtuse, apex nearly straight, with front angles obtuse; base much larger than apex; dorsum well convex, with sharply impressed median line reaching base and usually with a small round depression on each side at the level of the widest part; apical transverse impression well distinct, usually uneven; basal impressions wide, laterally joining basal fovea, which are small and narrow; basal area sharply striated; two pairs of marginal setae on each side, of which the anterior one lies just before the widest part and the posterior one not on hind angles but slightly advanced in front of them.

Pterothorax. Elytra oval, oblong (EW/EL = 1.25/1.60 = 0.78 in male holotype; 0.8 in average), widest at about four-ninths from bases, and equally narrowed toward bases and toward apices, dorsum strongly convex; shoulders rounded, thinly distinct, sides entirely bordered, rather strongly arcuate in basal third, less so in median parts, conjointly rounded at apices, each margin forming a distinct terminal point at the apical part; striae vestigial excepted stria 1 which is always sharply impressed throughout, striae 2–3 not traceable on the disc though very shallow, stria 8 impressed only behind the middle set of marginal umbilicate pores; scutellar striole well defined, bordered; apical striole short but distinct, divergent anteriorly, and free at anterior end; apical carina straight; two setiferous dorsal pores, usually foveolate, present on the site of stria 3 at 1/6 and about 2/3 from base respectively; preapical pore present and located at the 1/10 from apex; humeral set of marginal umbilicate pores nearly regular though not perfectly equidistant.

Legs short but robust; protibial furrow superficial. Meso- and metatibias short and straight. First two male protarsomeres distinctly and asymmetrically widened.

Aedeagus (fig. 3) robust, elongate. Median lobe, in lateral view, sharply curved at base, sublinear and regular along the central part, tapering from apical third toward apex; apex long, regularly thinned dorso-ventrally, sharply thinned in ventral or dorsal view, hook shaped at apical extremity. Basal bulb very long and enlarged, sagittal carina thin and long, extended to the dorsal part. Inner sac provided with a long, sclerified, twisted copulatory piece which is progressively enlarged at apex. Styles long, reaching the apical third of the median lobe, each provided with four long distal setae.

Derivatio nominis. It is a real pleasure to dedicate this new species to one of its collectors, our friend Dr. R. Chiori for her longstanding support to entomological researches in numerous countries.

Distribution. Known only from the northeastern slope of the Chimborazo volcano (Western Cordillera). Located within patches of Polylepis sp. forest, residual at elevations between 4300 and 4500 m along the ecotone between the grazed páramo and the lower part of the super-páramo.

Diagnostic characters: The general shape of the habitus relates this species to O. mateui Allegro et al., 2008 even though the latter have a far larger size (3.31–3.51 mm). Specimens of O. chioriae studied were not longer than 3.1 mm. Nevertheless, the aedeagus of the two species are very different. Aedeagus of O. chioriae n. sp. presents a general conformation close to O. guaguanus : the median lobe is stretched out, the tip progressively slender, regularly reducing to the apex and ending in a hook. However, the aedeagus’s apex presents a sickle extremity clearly not as developed as in guaguanus . Nevertheless, chioriae differs from guaguanus with a larger median lobe and a less ventrally straightened apex; the sagittal aileron is far less developed and is proportionally very small in chioriae . Concerning the habitus, O. chioriae ’s elytra are more oblong, more stretched out than for O. guaguanus whose general size is markedly smaller (2.8–2.9 mm). It is likely that O. chioriae constitutes, with different species of the Occidental Cordillera, i.e. mateui , guaguanus and most likely pierremoreti (even though the aedeagus representation of this species in Allegro et al., 2008 probably implies a damaged median lobe), a related-group of species by the aedeagus’s conformation and also by the shape of the habitus. Aedeagus of O. chioriae share, as well, a median lobe conformation analogous to that of O. moreti with an apical blade longer and slimmer at the apex. The base is widened, robust, and offers a thin sagittal blade but quite long which ventrally reduces at the level of the ostium.

Figures

FIGURE 2. Habitus of Oxytrechus chioriae n. sp., from the east side of the Chimborazo volcano, Ecuadorian páramo (Holotype).

FIGURES 3 A–C. Aedeagus of the holotype of Oxytrechus chioriae n. sp.—Left lateral view (A); —Ventral view (B); —Dorsal view (C); Scale bar: 300 µm.