Chasmogenus guianensis, 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 guianensis sp. nov. Figures 10C , 14G, H , 17 , 21F , 22C

Chasmogenus sp. X Short, 2013: 87 (in part); Short & Kadosoe, 2011: 87 (in part).

Type material.

Holotype (male): "Suriname: Sipaliwini District/ 2.47700N, 55.62941W, 275 m/ Camp 1, Upper Palumeu/ leg. A. Short; large sandy creek/ 14.iii.2012; SR12-0314-01A/2012 CI-RAP Survey", “[barcode]/SEMC1088252/KUNHM-ENT”, "HOLOTYPE/ CHASMOGENUS/ guianensis sp. n./ des. Smith & Short." (NZCS). Paratypes (235): Suriname: Para District: near Overbridge River Resort, 05°31.8'N, 055°03.5'W, 15-18-FEB-2010, Flight Intercept Trap, leg. P. Skelley, W. Warner, and C. Gillett (1 ex., SEMC). Sipaliwini District: same data as holotype (55 exs., NZCS, SEMC, including DNA Voucher SLE1826), same data as holotype except: 10.iii.2012, small forest pool, SR12-0310-02A (27 exs., SEMC); same data as holotype except: 10-12.iii.2012, large detrital pools, SR12-0310-01A (8 exs., SEMC); same data as holotype except: 11.iii.2012, large pool by trail, SR12-0311-01A (73 exs., SEMC, including DNA Vouchers SLE1827 and SLE1863); same data as holotype except: water held in dead palm leaf, SR12-0311-02A (1 ex., SEMC); same data as holotype except: 10-16.iii.2012, Flight Intercept Trap, SR12-0310-TN1 (44 exs., SEMC); Rapids on Kutari River, 2°19.280'N, 56°52.595'W, 224 m, 18.viii.2010, leg. A. E. Z. Short, 2010 CI-RAP Survey, forest stream, SR10-0818-01A (1 ex., SEMC); Camp 2 on Sipaliwini River 2°10.973'N, 56°47.235'W; 210 m, 28-29.viii.2010, leg. Short and Kadosoe 2010 CI-RAP Survey, large forest stream, SR10-0828-02A (1 ex., SEMC, DNA Voucher SLE1821); same data as previous except: 28.viii.2010, small detrital stream, SR10-0828-03A (1 ex., SEMC). Guyana: Region 6: Upper Berbice Basecamp 1, 4°09.289'N, 58°10.717'W, 96 m, 24.xi.2014, leg. Short, Salisbury, and La Cruz, margins of basecamp creek, GY14-0924-01A (15 exs., CBDG, SEMC, including DNA Vouchers SLE1616, SLE1836, and SLE1862); same data as previous except: 21.xi.2014, muddy detrital pools in drying creek bed near camp, GY14-0921-02A (5 exs., SEMC, including DNA Vouchers SLE1834 and SLE1835); Upper Berbice ca. 1 km south of Basecamp 1, 4°09.241'N, 58°10.627'W, 109 m, 25.ix.2014, leg. Short, Salisbury, and La Cruz, detritus pools in dry creek bed, GY14-0925-01D (3 exs., SEMC).

Differential diagnosis.

Among species that have a broad, rounded clypeal emargination, this species belongs to a group that have an aedeagal form with relatively broad, straight parameres and a wide median lobe which is slightly shorter to slightly longer than the apex of the parameres. It is distinctly smaller than C. amplius , C. berbicensis , and C. clavijoi . It is most similar to the comparably-sized C. brownsbergensis but the parameres are slightly wider and sublinear along the outer margins (Fig. 14G, H ). Examination of the aedeagus is the only way to definitively identify this species. Unassociated females may not be determined with certainty.

Description.

Size and color. Total body length 3.6-4.0 mm. Body form elongate oval with slightly curved lateral margins. Dorsum of head bicolored, frons dark orange-brown, clypeus and labrum dark orange to dark yellow-orange (Fig. 10C ). Pronotum and elytra dark orange-brown. Venter dark red-brown mesally, dark brown marginally. Head. Ground punctation on head moderately coarse. Clypeus with anteroposterior emargination, which exposes a rounded to angulate gap between clypeus and labrum (Fig. 10C ). Mentum moderately depressed in anterior half with rounded notch on anteromedial margin. Maxillary palps long, longer than width of head immediately posterior to eyes. Thorax. Ground punctation on pronotum moderately coarse. Prosternum even, not tectiform. Mesoventrite with very weak elevation forming a thin posteromedial longitudinal carina. Metafemora densely pubescent in basal nine-tenths. Aedeagus. Aedeagus (Fig. 14G, H ) with median lobe widest at base and very slightly tapering along entire length, terminating in a bluntly triangular apex which is distinctly shorter than the apex of the parameres. Sclerite of the median lobe not expanded. Gonopore situated nearly 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. three-quarters the length of the parameres.

Etymology.

This species is named after the Guiana Shield, the region of South America from which it is known. To be treated as a noun in apposition.

Distribution.

This species has been found at several localities in Guyana and Suriname (Fig. 17 ).

Biology.

This species was found in a variety of habitats including a forested swamp, ephemeral detrital pools, general creek margins and a large sandy creek (Fig. 21F ). It was also collected passively via a flight intercept trap. A single specimen was collected from water in a dead palm leaf on the ground.

Figures

Figure 10. Dorsal view of heads of Chasmogenus spp. from Suriname and Guyana A C. brownsbergensis B C. ligulatus C C. guianensis D C. pandus.

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 21. Habitat of Chasmogenus spp in Suriname. A Type locality and habitat for C. brownsbergensis, Brownsberg Nature Park (collecting event SR 12 - 0804 - 03 A) B type locality and habitat for C. ligulatus, near Mt. Kasikasima (collecting event SR 12 - 0320 - 02 A) C type locality and habitat for C. tafelbergensis, summit of Tafelberg tepui (collecting event SR 13 - 0817 - 01 A) D type locality and habitat for C. schmits, S of Kwamala along the Kutari River (collecting event SR 10 - 0316 - 01 B) E habitat for C. acuminatus, Central Suriname Nature Reserve, Raleighvallen (collecting event SR 16 - 0316 - 01 B) F habitat for C. guianensis, upper Palumeu River, (collecting event SR 12 - 0311 - 01 A).

Figure 22. Habitat of Chasmogenus spp in Guyana. A Type locality and habitat for C. berbicensis, Guyana, margin / detrital sandbar of the upper Berbice River (collecting event GY 14 - 0922 - 02 A) B type locality and habitat for C. undulatus Guyana, near Ayanganna airstrip (collecting event GY 14 - 0317 - 01 A) C habitat for C. acuminatus and C. guianensis, Guyana, small tributary of the upper Berbice River (collecting event GY 14 - 0924 - 01 A) D habitat for C. acuminatus (collecting event GY 13 - 1103 - 02 A).