Chasmogenus gato, Smith & Short, 2020

Smith, Rachel R. & Short, Andrew Edward Z., 2020, Review of the genus Chasmogenus Sharp, 1882 of northeastern South America with an emphasis on Venezuela, Suriname, and Guyana (Coleoptera, Hydrophilidae, Acidocerinae), ZooKeys 934, pp. 25-79 : 25

Chasmogenus gato sp. nov. Figures 9F , 14C , 17 , 20A

Type material.

Holotype (male): "Venezuela: Amazonas State/ 4°58.838'N, 67°44.341'W; 95m/ Communidad Caño Gato on Rio/ Sipapo; 16.i.2009; leg. Short/ Miller, Camacho, Joly, & García / VZ09-0116-01X: along stream", "[barcode]/ SM0843374/ KUNHM-ENT", "HOLOTYPE/ CHASMOGENUS/ gato sp. n./ des. Smith & Short" (MIZA). Paratypes (19): Venezuela: Amazonas: same data as holotype (14 exs., MIZA, SEMC, including DNA voucher SLE1202); River near Orinoco/Sipapo confluence, 5°03.707'N, 67°46.768'W, 92 m, 15.i.2009; leg K. Miller, detrital pools, VZ09-0115-01B (3 exs., SEMC); S. Communidad Porvenir, 5°20.514'N, 67°45.315'W, 87 m, 15.i.2009, leg. Short & García, pool in culvert, VZ09-0115-03A (1 ex., SEMC); ca. 15 km E. Puerto Ayacucho, 5°34.408'N, 67°30.283'W, 66 m, 6.i.2006, leg. A. E. Z. Short, stream at road crossing, AS-06-015 (1 ex., SEMC).

Differential diagnosis.

Of smaller species with a broadly rounded clypeal emargination, this species is similar in size, morphology, and general form of the aedeagus to C. clavijoi but can be differentiated by the slightly darker dorsal coloration, which is very dark brown.

Description.

Size and color. Total body length 3.3-3.8 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head bicolored, frons and clypeus pale to dark brown, labrum pale yellow-brown (Fig. 9F ). Pronotum and elytra dark orange-brown to dark brown. Head. Ground punctation on head fine, slightly finer on labrum. Clypeus with anteromedial emargination, which exposes a rounded to angulate gap between the labrum and clypeus (Fig. 9F ). Mentum moderately depressed in anterior half with subtriangular notch. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation on pronotum fine. Prosternum very weakly tectiform. Mesoventrite with weak elevation forming a posteromedial longitudinal carina. Metafemora densely pubescent in basal nine-tenths. Aedeagus. Aedeagus (Fig. 14C ) with median lobe widest at base and very slightly tapering until apical fifth, then narrowing to form an acute triangular apex which is even with the apex of the parameres. Sclerite of the median lobe not expanded. Gonopore situated less than half of one gonopore width below the apex of the median lobe. Parameres symmetrical, with outer margins straight, with apex slightly inwardly curved and bluntly rounded. Basal piece long, ca. four-fifths the length of the parameres.

Etymology.

The species is named after the community of Caño Gato, from where the species was collected. To be treated as a noun in apposition.

Distribution.

Known from several closely situated localities in southern Venezuela (Amazonas) (Fig. 17 ).

Biology.

This species has been collected in stream margins and associated stream habitats such as nearby detrital pools (Fig. 20A ).

Figures

Figure 9. Dorsal view of heads of Chasmogenus spp. A C. amplius B C. acuminatus C C. berbicensis D C. clavijoi E C. undulatus F C. gato.

Figure 14. Aedeagi of (dorsal view) of Chasmogenus spp. A C. amplius B C. clavijoi C C. gato D C. berbicensis E C. brownsbergensis F C. schmits G, H C. guianensis G specimen from Suriname H specimen from Guyana. Scale bar: 0.25 mm.

Figure 17. Distribution of Chasmogenus spp.

Figure 20. Habitat of Chasmogenus spp. A Type locality and habitat for C. amplius and C. gato, Venezuela: Amazonas, Cano Gato (collecting event VZ 09 - 0116 - 01 X) B type locality and habitat for C. clavijoi, Venezuela: Guarico, San Nicolasito Field Station (collecting event VZ 09 - 0110 - 02 X) C-F habitat for C. australis: C Venezuela, Barinas, 13 km southeast of Ciudad Bolivia (collecting event VZ 12 - 0125 - 02 A) D Guyana, near Kusad Mountains (collecting event GY 13 - 1027 - 01 A). E, F Brazil, Roraima, near Caracarai, red circles showing live individuals of C. australis floating on the water surface (collecting event BR 18 - 0116 - 05 A).