Helobata amazonensis, Clarkson, Bruno, Santos, André Dias Dos & Ferreira-Jr, Nelson, 2016

Clarkson, Bruno, Santos, André Dias Dos & Ferreira-Jr, Nelson, 2016, On Brazilian Helobata Bergroth, 1888 (Coleoptera: Hydrophilidae): description of two new species, new records, and key to species, Zootaxa 4126 (4), pp. 548-562 : 550-552

Helobata amazonensis sp. nov.

(Figs. 1–6)

Type material. Holotype (male): “ Brasil, AM, R. Amazonas, Itacoatiara,/ Ilha da Trindade, Paraná da Trindade,/ - 3,31345o -58,73231o/ Luz U.V., A17UV/ 22 - IX- 2003,/ P. de Marco & N. Ferreira-Jr.”( INPA, in ethanol).

Diagnosis. Moderate-sized species (about 5.70 mm in length). Dorsum yellow with conspicuous brown areas; head and pronotum with very weak metallic sheen; pronotum with well-defined central brown area; elytra with faint light brown spots on humeral humps and diffusely spread throughout elytral disc (Fig. 1); abdominal ventrites yellow (Fig. 2). Clypeal disc and frons without microsculpture on interstices of ground punctuation; fine and very short decumbent setae distributed on anterior half of the clypeus, absent on frons; anterior clypeal margin convex, slightly truncate medially (Figs. 1–2); frontoclypeal suture distinct (Fig. 1). Maxillary palpomere 3 and 4 subequal in length (Fig. 2). Mentum without conspicuous microsculpture. Punctures on elytral rows fine, regularly spaced (Fig. 1). Posteromedial elevation on mesoventrite semi-trapezoidal, very wide, with strongly raised lateral carinae, oblique, widely distant each other, converging anteriorly; widely connected with the metaventral projection (Fig. 2). Metaventral projection (between mesocoxae) forming an elevated longitudinal carina, strongly and widely connected posteriorly with metaventral medial carina. Metaventral medial carina rises gradually until connecting to metaventral projection (Fig. 2). Maximum width of phallobase at about half its length; manubrium short and narrow, rounded at the base. Parameres longer than median lobe; inner margins in ventral view sinuate, slightly concave on basal quarter, convex on two-fourths of inner margin length, concave on apical half; outer margins convex; apex slightly truncate, strongly bent inwards. Median lobe with shallow apical emargination on dorsal lobule; ventral lobule much shorter than dorsal lobule, not visible in dorsal view, apex rounded, strongly produced ventrally as a tooth, visible in lateral view (Figs. 3–6).

Description. Holotype male: total length 5.76 mm; maximum width 3.24 mm; maximum width of head 1.47 mm; elytral length 3.38 mm; maximum width of pronotum 2.92 mm.

Habitus (Figs. 1–2). Body broadly oval, dorsoventrally depressed. Dorsum yellow with conspicuous brown areas; slight metallic sheen on the head and pronotum. Clypeus yellow with postero-central brown area; frons brown. Pronotum with well-defined central brown area. Elytra with elongated light brown spots on humeral humps (interstriae 7 and 8), and light brown spots diffusely spread throughout elytral disc. Antennae, maxillary and labial palpi uniformly light brown. Ventral face of head and thoracic plates light brown, abdominal ventrites yellow. Legs light brown with pubescent portion on femora slightly darker.

Head. Clypeus and frons finely and densely punctate, punctures irregularly spread and shaped, about 2– 4 x smaller than one ommatidium; interstices of the clypeal disc and frons without microsculpture; fine and very short decumbent setae distributed on anterior half of the clypeus, absent on frons. Anterior clypeal margin convex, slightly truncate medially, rounded laterally (Figs. 1–2); frontoclypeal suture distinct (Fig. 1). Eyes deeply emarginated, interocular distance about 3x width of one eye in dorsal view (Fig. 1). Maxillary palpi longer than maximum width of head (1.2x longer) (Fig. 2); palpomere 1 minute, palpomere 2 longer than palpomere 3, palpomere 3 and 4 subequal in length, palpomere 4 asymmetrical with straighter inner face. Labial palpi about half the width of mentum. Mentum wider than long (about 1.4x wider) (Fig. 2); anterior margin strongly bisinuate, with central rounded notch (Fig. 2); surface strongly irregular, without conspicuous microsculpture, with regularly scattered fine setiferous punctures (Fig. 2).

PLATE 1. Figs. 1 to 6. Helobata amazonensis sp. nov. habitus: 1: dorsal view, 2: ventral view; aedeagus: 3: dorsal view, 4: ventral view, 5: lateral view, 6: ventro-lateral view.

Thorax. Ground microsculptures on pronotum, scutellar shield and elytra densely reticulate, shagreened, with fine and very short decumbent setae regularly spread throughout surface; punctation on pronotum densely distributed, fine punctures on pronotal disc irregularly shaped, about the same width of those on front (Fig. 1). Scutellar shield subtriangular, rounded posteriorly, longer than wide (Fig. 1). Elytra with ten distinct longitudinal rows of punctures in dorsal view; punctures on rows fine, about the same size of ommatidium, regularly spaced; punctures on 10th row barely impressed (Fig. 1). Prosternum finely pubescent, convex, not carinate medialy, with irregular surface (Fig. 2). Meso- and metaventrite finely pubescent. Posteromedial elevation on mesoventrite semitrapezoidal in ventral view, very wide (1.75x longer than wide), with strongly raised lateral carinae, oblique, converging and widely distant anteriorly, medial portion slightly convex with irregular surface, posteriorly projected between mesocoxae, widely connected with the metaventral projection (Fig. 2). Metaventral projection (between mesocoxae) forming an flat elevated longitudinal carina, strongly and widely connected posteriorly with metaventral medial carina. Metaventral medial carina rises gradually until connecting to metaventral projection (Fig. 2). Median and hind femora pubescent on basal five-sixths (Fig. 2).

Abdomen. Surface of ventrites even, without medial carina, with smooth lateral and posterior margins, evenly and finely pubescent. Ventrite 5 with shallow posteromedial emargination, semi-triangular, twice wider than deep, and lined with coarse spine-like setae (Fig. 2). Aedeagus (Figs. 3–6) 1.14 mm long. Phallobase symmetrical, short, much shorter than apical portion (ca. 0.13x the aedeagus in length), 1.9x wider than long, maximum width on about half of its length; manubrium distinct, short and narrow, rounded at base, about 0.25x the length of phallobase. Parameres longer than median lobe, inner margins in ventral view sinuate, slightly concave on basal quarter, convex on two-fourths of inner margin length, concave on apical half; outer margins convex, strongly narrowed at apical third, apex slightly truncate, strongly bent inwards. Median lobe thick, dorsal lobule with shallow apical emargination (ca. 0.05x length of median lobe), ventral lobule much shorter than dorsal lobule (ca. 0.76x length of median lobe), conspicuously shorter than apical emargination, not visible in dorsal view; apex rounded, strongly produced ventrally as a tooth, visible in lateral view.

Etymology. The specific name amazonensis refers to the Amazonas river basin, the type locality of the species. The Latin suffix -ensis denotes place, locality, country; it may also refer to “amazonense”, ethnicity of those native from Brazilian Amazonas state.

Distribution. Known only from its type locality in Amazonas State, North Brazil.

Remarks. Based on the original descriptions, the new species can be distinguished from others by the convex anterior margin of clypeus (substraight and slightly produced anterolaterally in H. corumbaensis , Figs. 12 and 13; sinuate and strongly produced anterolaterally in H. quatipuru , Figs. 20 and 21); by distinct frontoclypeal suture (absent in H. bitriangulata , see Fig. 1c of García 2000); by fine punctures on elytra (thicker in H. perpunctata ; unknown in H. bitriangulata , H. cuivaum , H. lilianae , H. soesilae and H. aschinakiranae ), by straight, laterally oblique carinae of the posteromedial elevation on mesoventrite (sinuate in H. bitriangulata , see Fig. 2f of García 2000; slightly concave anteriorly, strongly divergent posteriorly and almost connected anteriorly in H. cuivaum , see Fig. 2e of García 2000; slightly convex and almost connected anteriorly in H. lilianae , see Fig. 2d of García 2000; convex posteriorly in H. corumbaensis and in H. quatipuru , Figs. 13 and 21); by parameres length in relation to the median lobe (as long as median lobe in H. corumbaensis , unknown in H. bitriangulata ); by the inner margins of parameres sinuate in ventral view (concave in H. pantaneira sp. nov., Fig. 10; very slightly sinuate in H. larvalis and H. perpunctata , see figs. 5 and 15 of Fernández & Bachmann 1987; unknown in H. bitriangulata ); by shallow apical emargination on dorsal lobule (deep in H. aschinakiranae , H. cossyphoides , H. cuivaum , H. lilianae and H. pantaneira sp. nov.; unknown in H. bitriangulata ); by the ventral lobule much shorter than dorsal lobule (as long as dorsal lobule in H. quatipuru , Figs. 22 and 23; and somewhat shorter in H. corumbaensis , Fig. 15; unknown in H. bitriangulata ); by the apex of ventral lobule not visible in dorsal view (visible in H. corumbaensis , H. cuivaum , H. larvalis , H. lilianae and H. quatipuru , unknown in H. aschinakiranae and H. bitriangulata ); and by the strongly produced ventrally apex (not produced in H. larvalis ; weakly produced in H. corumbaensis , H. pantaneira sp. nov., H. perpunctata ; unknown in H. aschinakiranae , H. bitriangulata , H. cuivaum , H. lilianae and H. soesilae ). Despite having ventral plates of head and abdomen completely and homogeneously colored, the sole specimen of the new species is quite pale (mainly on abdomen) and seems to be teneral. It will not be a surprise if variations on coloration are found after discovering of additional specimens to the species.

We were unable to distinguish between H. soesilae and H. amazonensis sp. nov based on the original description and illustration of H. soesilae . In order to confirm the hypothesis of H. amazonensis being a new species, we sent pictures to Dewanand Makhan, author of the Surinamese species, who kindly provided the assertion that these two species were not the same.