Chasmogenus itatiaia, Clarkson, Bruno & Ferreira-Jr, Nelson, 2014

Clarkson, Bruno & Ferreira-Jr, Nelson, 2014, Four new species and first nominal record of Chasmogenus Sharp, 1882 (Coleoptera: Hydrophilidae) from Brazil, Zootaxa 3765 (5), pp. 481-494 : 487-489

Chasmogenus itatiaia sp. nov.

(Figs. 3, 4, 13, 14, 15, 26 and 29)

Type material. Holotype (male): “ BRASIL: Rio de Janeiro,/ Itatiaia , Parque Nacional/ de Itatiaia ,/ 09.IV.2006,/ Poça no caminho das Agulhas Negras/ 22°23'05.4"S 44°40'41.7" O,/ Braga, R. B. col.” ( DZRJ, Coleoptera 2798 ); Paratypes (14): BRAZIL: Minas Gerais State: Itamonte Municipality: Brejo da Lapa, “ 01.X.1993, Ferreira-Jr, N. & Carvalho, A. L. col” (1 ex.: DZRJ, Coleoptera, 1774 ), “ 07.IV.2005, Moreira, F. F. F. col” (4 ex.: DZRJ, Coleoptera, 2779 ); Maciço de Itatiaia , Serra Negra, “Poça no pico da serra, 23.XI.2008, Clarkson, B. & Ferreira-Jr, N. col.” (3 ex.: DZRJ, Coleoptera, 2827 ); Rio de Janeiro State: Itatiaia Municipality: Same data as Holotype (4 ex.: DZRJ, Coleoptera, 2775 ; 2 ex.: SEMC).

Diagnosis. Large-sized species (6.0– 6.25 mm). Head densely covered with punctures. Anterior clypeal margin rounded, emargination very reduced to absent. Anterior margin of labrum deeply concave medially. Anterocentral notch on mentum developed, wide and rounded (Figs. 13, 14 and 15). General dorsal punctures of pronotum and elytra moderately coarse, only slightly smaller than systematic punctures. Elytra with four quite indistinct longitudinal rows of systematic punctures in dorsal view, (Fig. 3). Prosternum slightly carinate posteriorly (Fig. 29). Mesoventral carina very weak, restricted to posterior half (Fig. 4). Hind femora pubescent on basal five-sixths (Fig. 4). Ventrite 5 with very shallow posteromedial emargination (Figs. 4). Phallobase elongated, manubrium weakly distinct, wide. Parameres slightly shorter than median lobe, inner margin emarginated in apical fifth, outer margin subparallel to somewhat concave medially. Median lobe wide, thicker at base, constricted medially, gradually narrowing apicad on distal two-fifths, apex blunt; basal apophyses slightly convex, within parameres (Fig. 26).

The new species can be easily distinguished from other Neotropical species due to its very large size (6.05– 6.20 mm), being the largest species of the genus described to date. It differs from the other South American species by the very reduced medial notch between clypeus and labrum, in some specimens this medial notch is absent (in this character, it resembles the Central American species C. barrae Short and C. lorenzo Short ) and by the coarse dorsal punctures of pronotum and elytra which are obscuring the systematic punctures (by this character it resembles the Central American species C. ruidus Short and C. schoedli Short , and C. ubatuba sp. nov. described below). The absence of the strong carina raised into a “tooth” on the mesoventrite distinguishes this species from the Venezuelan species C. bariorum , C. occidentalis and C. yukparum . The overall shape of the male genitalia is diagnostic for this species (Fig. 13): some characteristics are shared with other Neotropical species as parameres slightly shorter than median lobe (South-American species: C. australis , C. bariorum , C. occidentalis , C. yukparum ; Central-American species C. barrae , C. lorenzo , C. ruidus , C. schoedli ), with outer margin subparallel to somewhat concave medially ( C. lilianae ) and median lobe constricted medially and gradually narrowing apicad ( C. occidentalis and C. sapucay ); the large-sized aedeagus, phallobase elongated with manubrium wide and weakly distinct, with the basal margins rounded distinguish this species from the other Neotropical species.

Description. Holotype male.

Size and form. Total length 6.15 mm; maximum width 2.85 mm; maximum width of head 1.30 mm; elytral length 3.75 mm; maximum width of pronotum 1.95 mm. Body broadly oval, moderately convex (Fig. 3).

Color. Dorsum of head, pronotum and elytra uniformly dark brown, lateral and anterior margins of pronotum and lateral and apical margins of elytra often slightly paler (Fig. 3). Maxillary and labial palpi pale brown. Antennae with antennomeres 1–5 pale brown, club dark brown (Fig. 4). Ventral face dark brown; lateral part of pronotum and epipleuron brown; legs brown with pubescent portion of femora dark brown (Fig. 4).

Head. Ground punctation on clypeus, frons and labrum moderately coarse, distance between punctures 0.5– 1.5× the width of one puncture. Systematic punctures on labrum consisting of scattered punctures, slightly larger than surrounding punctures, almost indistinct. Clypeus with an irregular row of distinct systematic punctures on both anterolateral portion, and some scattered ones, about 2.0–3.0× larger than surrounding punctures, bearing short, fine setae. Frons with irregular row of distinct systematic punctures along frontoclypeal suture at both sides and scattered systematic punctures mesally of eyes, both about 2.0–3.0× larger than surrounding punctures and bearing short, fine setae. Anterior clypeal margin rounded, without emargination. Anterior margin of labrum very concave medially. Mandibles bifid at apex. Maxillary palpi about as long as maximum width of head; apical and penultimate palpomeres subequal in length, palpomere 2 slightly longer than penultimate palpomere (1.2× as long as penultimate one) (Figs. 3 and 4). Labial palpi length about a half the width of mentum; ultimate palpomere with a preapical long seta (e.g. Fig. 12). Mentum bare, rather punctuate, somewhat rugose, with notch on anterolateral margin and deeply depressed on anterocentral half, anterocentral notch developed, wide and rounded (Figs. 13, 14 and 15).

Thorax. Ground punctation on pronotum and elytra evenly distributed and moderately coarse. Pronotum with two anterolateral and two posterolateral series of systematic punctures with long fine setae, each systematic puncture at least 2.0× the size of surrounding ground punctures: anterior series forming an irregular dense row curved backwards, beginning near anterolateral corners toward medial portion of pronutum; posterior series forming an irregular row on posterior half, perpendicular to lateral margins, beginning near of margin, restricted to lateral quarter (Fig. 3). Pronotal margins completely rimmed; lateral margins with sparse row of setiferous punctures on anterior two-thirds; posterior margin slightly arcuate (Fig. 3). Elytra with four quite indistinct longitudinal irregularly spaced rows of systematic punctures in dorsal view, slightly larger than ground punctures, sometimes only distinguishable by bearing rather long, fine setae; sutural stria strongly impressed on posterior twothirds (Fig. 3). Prosternum finely pubescent, weakly convex, slightly carinate medially on posterior portion (Fig. 29). Mesoventrite slightly convex medially on posterior half, with a very weak longitudinal carina on medial part (Fig. 4). Metaventrite with posteromedial, enlongate oval glabrous area, slightly longer than wide, about two-thirds of total length of metaventrite (Fig. 4). Hind femora pubescent on basal five-sixths (Figs. 4).

Abdomen. Ventrites densely pubescent, with pubescence on ventrite 1 slightly less dense centrally. Ventrite 5 with very shallow apical emargination, wider than deep, and lined with coarse yellow setae (Fig. 4). Aedeagus (Fig. 26) about 1.0 mm in length. Phallobase well developed, elongated, symmetrical, shorter than apical portion (ca. 0.40x the aedeagus in length), maximum width on apical third; manubrium weakly distinct, wide, rounded at base, about half the length of phallobase. Parameres slightly shorter than median lobe, evenly wide from base to apical three-fifths, were gradually narrowing apicad, inner margin emarginated on apical fifth in dorsal view, outer margin subparallel to somewhat concave medially; apex rounded, slightly turned inwards. Median lobe wide, thicker at base, constricted medially, gradually narrowing apicad on apical two-fifths, apex blunt; corona distinct, oval, wider than longer, subapical (on apical third-fifths); basal apophyses slightly convex, within parameres, almost extended into phallobase.

Variation. Body length from 6.05 mm to 6.20 mm. The emargination of the anterior clypeal margin is always present but reduced to almost absent in some specimens. Significant variation in coloration and sexual dimorphism in the external morphology was not observed in the type specimens.

Etymology. The specific name refers to the Itatiaia National Park localized in the frontier between Minas Gerais, Rio de Janeiro and São Palo States, from where the type specimens were collected. Noun in apposition.

Biology. All type specimens of C. itatiaia sp. nov. were collected from ponds, among the vegetation, in mountainous areas about 2.400 m a.s.l., where the temperature may range between 0o– -2o C in the winter.

Remarks. As pointed above for C. fluminensis sp. nov., the altitude and temperature observed on the distribution of the species may have influence on the total size of the body. But it may be easier to observe in species like C. fluminensis sp. nov. in which the large distribution and number of species provides information as the variation of the body length suiting with the altitudinal gradient. On the other hand, C. ubatuba sp. n was collected near sea level and possesses large specimens in the type series. Since C. itatiaia sp. nov. and C. ubatuba sp. nov. are known only from the type-locality and nearby areas we cannot infer anything about the influence of the environment on the size of these species and even considering only C. fluminensis sp. nov. some morphometric and ecological analyses are needed to confirm this hypothesis.