Chasmogenus cajuina, Alves & Clarkson & Lima, 2020

Alves, Tayná, Clarkson, Bruno & Lima, Lucas Ramos Costa, 2020, A new species of Chasmogenus Sharp, 1882 and new records of Hydrophilidae (Coleoptera) from Northeastern Brazil, Zootaxa 4763 (4), pp. 579-586 : 580-583

Chasmogenus cajuina sp. nov. Alves, Clarkson & Lima

Figs. 1–8

Type material. Holotype (male): “ Brasil: Piauí, Castelo do Piaui,/ Cachoeira das Arraias ,/ 5°11’28.5”S, 41°42’03.2”W, 174m / 12.III.2016, Silva, G. R. leg. ( CEHJ 354 )” ( MNRJ) . Paratypes (17): Brazil. Piauí State. Castelo do Piauí Municipality: Same data as Holotype (2 exs.: MNRJ; 2 exs.: DZUP; 2 exs.: MZSP; 2 exs. SEMC); Alto Longá Municipality: “ Cachoeira da Campeira ,/ 5°11’45.1” 42°15’33.9, 177m,/ 05.IV.2017, Lima, L. R.C. leg. ( CEHJ 462 )” (2 exs.: NMPC); “ 5°11’45.1”S, 42° 6’47.70”W, 17.II.2018, Alves, T.S. leg.” (1 ♂, 1♀: CE- UFPE); Novo Santo Antônio Municipality: “ Cachoeira da Coruja , 5°22’02.6”S, 41°59’52.9”W, 29.III.2018, Alves, T.S. leg.” (1 ♂, 1♀: CE-UFPE); Piripiri Municipality: “ Cachoeira do Bota Fora , 4°12’51.1”S, 41°40’01.7”W, 15.XII.2018, Alves, T.S. leg.” (2 ♂, 1 ♀: CE-UFPE).

Diagnosis. Medium-sized species (3.35–4.00 mm). Head densely punctated ( Fig. 4 ). Anterior clypeal margin with deep emargination, subtriangular, with lateral margins convex, exposing a gap between clypeus and labrum ( Fig. 4 ). Anterior margin of labrum slightly concave medially. Anterocentral notch on mentum, developed and concave ( Fig. 5 ). General dorsal punctures of pronotum and elytra evenly distributed, moderately coarse, slightly smaller than systematic punctures in dorsal view ( Fig. 1 ). Elytra with indistinct rows of irregularly spaced systematic punctures about the same size to 2.0× larger than surrounding ground punctures, bearing long, fine setae ( Fig. 1 ). Prosternum slightly carinate posteromedially. Mesoventral carina restricted to posterior half, well defined and slightly raised ( Fig. 2 ). Hind femora almost completely pubescent, bare on apical eighth ( Fig. 2 ). Ventrite 5 with shallow posteromedial emargination, distinctly wider than deep, and lined with 12 coarse yellow setae ( Fig. 2a ). Phallobase long, manubrium distinct, narrow. Parameres slightly shorter than median lobe, inner margin slightly emarginate on apical fifth in dorsal view, outer margin subparallel basally, each apex with 2–3 minute spines. Medi- an lobe wide, gradually narrowing apicad, apex strongly acuminate; basal apophyses subparallel, within parameres, extended into phallobase ( Figs. 6–7 ).

The new species can be distinguished from other Neotropical species mainly for the male genitalia characteristics ( Figs. 6–8 ): having median lobe wide, gradually narrowing apicad, apex strongly acuminate and slightly longer than parameres; gonopore placed subapically, distinct semicircular; basal apophyses within parameres; outer margin of each paramere slightly convex, inner margin slightly convex basally and slightly concave subapically; apex rounded, slightly turned inwards, with 2–3 minutes spines.

Size and form. Total length 3.72 mm; maximum width 2.12 mm; maximum width of head 1.05 mm; elytral length 2.43 mm; maximum width of pronotum 1.89 mm. Body broadly, oval and moderately convex.

Color. Dorsum of head, pronotum and elytra dark brown with the frons and clypeus often darker ( Figs. 1 and 4 ); labrum brown, anterior margin lighter. Maxillary and labial palpi pale brown. Antennae with antennomeres 1–5 pale brown, club darker ( Fig. 5 ). Ventral face dark brown; lateral part of pronotum and epipleuron light brown; legs dark brown with pubescent portion of femora darker ( Figs. 2–3 ), tarsi pale brown.

Head. Ground punctation on labrum, clypeus and frons coarse, distance between punctures 0.5–0.9× the width of one puncture ( Fig. 4 ). Systematic punctures on labrum consisting of some punctures about 1.5× the diameter of surrounding punctures, forming an irregular row of scattered punctures on median portion, sometimes bearing short, fine setae. Clypeus with an irregular row of distinct systematic punctures on anterior portion, in both sides, with few scattered ones, about 2.0–3.0× larger than surrounding punctures, bearing short, fine setae ( Fig. 4 ). Frons with irregular row of distinct systematic punctures along frontoclypeal suture, about 2.0–3.0× larger than surrounding punctures and some less distinct scattered systematic punctures mesally of eyes, both bearing short, fine setae. Anterior clypeal margin with deep emargination, subtriangular, with lateral margins convex, exposing a gap between clypeus and labrum ( Fig. 4 ). Anterior margin of labrum slightly concave medially. Maxillary palpi as long as the maximum width of head; palpomere 1 minute, palpomere 2 0.3× longer than palpomere 3, palpomeres 3 and 4 subequal in length ( Fig. 4 ). Labial palpi about half the width of mentum; ultimate palpomere with a preapical long seta and a short apical seta ( Fig. 5 ). Mentum bare and smooth, anterior portion very depressed on anterocentral half with a deep notch on anterolateral margin; anterocentral notch on a raised anterior margin, developed and concave ( Fig. 5 ).

Thorax. Ground punctation on pronotum and elytra evenly distributed, moderately coarse, slightly smaller than systematic punctures in dorsal view. Pronotum, in dorsal view, with two anterolateral and two posterolateral series of systematic punctures with long, fine setae, 1.5–2.0× the size of surrounding ground punctures: anterior series forming an regular row curved backwards, beginning near anterolateral corners toward medial portion of pronotum; posterior series forming an irregular row on posterior half, perpendicular to lateral margins, beginning near of margin, restricted to lateral quarter ( Fig. 1 ). Pronotal margins completely rimmed; lateral margins with some sparse systematic punctures; posterior margin slightly arcuate ( Fig. 3 ). Elytral disc with two longitudinal rows of systematic punctures about the same size to 1.5× larger than surrounding ground punctures; inner row somewhat indistinct with very sparse punctures irregularly spaced, bearing very short and fine setae in posterior half of elytral length; outer row distinct, duplicate, irregular, with irregularly spaced punctures bearing long, fine setae throughout elytral length; sutural stria strongly impressed on posterior three-fifths ( Fig. 1 ). Elytron in lateral view with indistinct rows of irregularly spaced systematic punctures about the same size to 2.0× larger than surrounding ground punctures, bearing long, fine setae. Prosternum finely pubescent, weakly convex, slightly carinate posteromedially ( Fig. 2 and 5 ). Mesoventrite with a longitudinal carina on medial part, restricted to posterior half, well defined and slightly raised ( Fig. 2 ). Metaventrite with posteromedial, elongate oval glabrous area, slightly longer than wide, about half the total length of metasternite ( Fig. 2 ). Hind femora almost completely pubescent, bare on apical eighth ( Fig. 2 ).

Abdomen. Ventrites densely and evenly pubescent. Ventrite 5 with shallow posteromedial emargination, distinctly wider than deep, and lined with 12 coarse yellow setae ( Fig. 2a ). Aedeagus ( Figs. 6–8 ) about 0.63 mm in length. Phallobase well developed, 1.3× longer than wide, symmetrical, shorter than apical portion (ca. 0.46x the aedeagus in length), maximum width on apical third; manubrium distinct, narrow, rounded at base, about half the length of phallobase. Parameres slightly shorter than median lobe, evenly wide from base to apical third, where gradually narrowing apicad, inner margin slightly emarginate on apical fifth in dorsal view, outer margin subparallel basally; apex rounded, slightly turned inwards, with 2–3 minute spines ( Fig. 8 ). Median lobe wide, gradually narrowing apicad, apex strongly acuminate; gonopore distinct, semicircular, wider than longer, subapical (on apical seven-tenths); basal apophyses subparallel, within parameres, extended into phallobase.

Variation. Body length from 3.35 mm to 4.00 mm. Relevant variation on coloration and sexual dimorphism in the external morphology was not observed in the type specimens.

Etymology. The specific name “ cajuina ” (from Portuguese “cajuína”) is dedicated to the famous cashew-based drink, symbol of the State of Piauí. The name stands as a noun in apposition.

Biology. The type and additional material were collected near flowing water from potamal and ritral sections of streams on backwater margins. The specimens were collected mainly in low altitude regions from 68 to 177 m.a.s.l., in area of the ecotone between Cerrado and Caatinga ecosystems.

Distribution. Brazil, Piauí State: Municipalities of Alto Longá, Castelo do Piauí, Novo Santo Antônio, and Piripiri.

Figures

FIGURES 1–8. Chasmogenus cajuina sp. nov. 1–3) Habitus: 1, dorsal view; 2, ventral view (2a, detail of last ventrite); 3, lateral view. 4) Head in dorsal view. 5) Head in ventral view and prosternum. 6–8) Aedeagus: 6) ventral view; 7, dorsal view; 8, detail of apical half.