Gyrinus (Neogyrinus) sabanensis, Gustafson & Short, 2017

Gustafson, Grey T. & Short, Andrew E. Z., 2017, Review of the whirligig beetle genus Gyrinus of Venezuela (Coleoptera: Gyrinidae), Acta Entomologica Musei Nationalis Pragae 57 (2), pp. 479-520 : 499-500

Gyrinus (Neogyrinus) sabanensis sp. nov.

( Figs 1 , 30 , 56 , 69 , 75 )

Type material. HOLOTYPE: J, ‘ VENEZUELA: Bolivar State / 5°40›24.8»N, 61°24›11.3»W, 1330 m / unnamed river; 2.viii.2008 / leg. A. Short, M. García, L.Joly / AS-08-066; small side stream [white label, typed black ink]’, ‘ SEMC0878700 / KUNHM-ENT [white label, typed black ink with barcode]’ ( MIZA) . PARATYPES (3 spec.): same as holotype but, SEMC0878691 , SEMC0878696 ; and 5°44’35.6”N, 61°24’11.2”W, 1305 m, Rio Mareman Paru , 2.viii.2008, AS-08-065 ; various river habitats, SM0828809 ( MIZA, SEMC).

Diagnosis. Body form ( Fig. 1 ) broadly oval, strongly convex in lateral view; pronotal and elytral margins broad, pronotal margins darkly colored, elytral margins lightly colored yellowish-orange to red; elytral disc with non-uniform reticulation, medially appearing polished, laterally bronzy-metallic in appearance; striae VI–XI evident with mostly distinct ovoid punctures, VIII–IX with punctures linear basally becoming distinct apically; striae VIII–X sulcate, elytral stria Xweakly impressed basally, sulcate apically; elytral intervals all similarly convex; elytral apex obliquely truncate, border absent, epipleural angle indistinct; metanepisternal ostiole absent; aedeagus ( Fig. 31 ) withmedian lobe justlongerthan parameres, narrow, very weakly attenuated towards apex, apex laterally parallel-sided, broadly rounded apically; gonocoxae ( Fig. 56 ) elongate, apices obliquely truncate with lateral angle distinct. Description. Size. Length = 3.5–4.0 mm, width = 2.0– 2.5 mm. Habitus. Body form broadly oval, attenuated anteriorly and very weakly so posteriorly, widest point at elytral humeral angle; in lateral view strongly dorsoventrally convex, greatestconvexity posterior toscutellar region, weakly depressed anteriorly, strongly depressed posteriorly.

Coloration ( Fig. 1 ). Dorsally, head, pronotum, elytral disc bronzy-green, lateral margins of pronotum similarly colored as remainder of pronotum, elytral lateral margin lightly colored yellowish-orange to red; ventrally lightly colored, mouthparts, ventral surface of pedicel, hypomeron, elytral epipleuron, light yellow, remainder of venter slightly darker yellow to orangish-yellow in color.

Sculpture and structure. Pronotumwith broadlateral margins. Elytra with striae I–V weakly present, evidentas reticulate stripes, Vwith variously developedweakly impressed punctures; VI–XI evident, mostly composed of distinct ovoid punctures; VI with small faintly impressed ovoid punctures; VII ovoidpunctures larger than VI; striae VIII–IX sulcate, basally punctures linear, apically becomingdistinct ovoid punctures; stria Xweaklyimpressed basally becoming sulcate apically; stria XI raised above elytral margin in basal half, marginal apically. Elytral interval Ientirely and intervals II–VI apically, with reticulation composed of meshes with small sculpticells, producing a polished appearance; intervals II–VI basally with reticulation more strongly impressed, meshes composed of larger sculpticells producing a metallic appearance; intervals VII–XI entirely with more strongly impressed metallic reticulation; all elytral intervals evenly convex. Elytra without medial pre-apical plica; lateral margin of elytra separated from apex by plica; apices obliquely truncate; border absent; epipleural angle indistinct, never with denticle. Metanepisternal ostiole absent. Ultimate abdominal tergite without strong medial acumination.

Male genitalia ( Fig. 30 ). Aedeagus with median lobe just longer than parameres, weakly narrowing apically, parallel-sided in apical 1/4, apex broadly rounded, bifid medially; parameres with apex truncate, weakly emarginate paramedially. Female genitalia ( Fig. 56 ). Gonocoxae elongate, apicesobliquely truncate, lateralangle distinct, left gonocoxasomewhat broader than right.

Variability. The few specimens examined differed in howlinear the punctures of elytralstriae VIII–IX appeared basally, and for how long the lineate region extended along these striae. The two female paratypes are also larger in size than the male holotype.

Differential diagnosis. Gyrinus sabanensis sp. nov. is most similar to G. ovatus , in terms of general appearance, but can be easily distinguished from G. ovatus by having elytral striae VIII–IX sulcate, with linear punctures basally, that become distinct apically but remain ovoid in shape, as opposed to having elytral striae VI–IX sulcate with round punctures that are distinct throughout the entirety of the stria. Furthermore, the elytral apices differ strongly between the two species. In G. sabanensis sp. nov. the elytral apex is not bordered, the epipleural angle is indistinct, and the elytral lateral margin is separated completely from the apex by a plica, as opposed to G. ovatus in which the elytral apex is incompletely bordered, the epipleural angle is distinct and often possessing a denticle, and the elytral lateral margin is not separated from the apex by a plica. Finally, the aedeagus differs pronouncedly between the two species as G. sabanensis sp. nov. has the medial lobe weakly attenuated apically, is just longer than the parameres, and has the apex broadly rounded and nearly parallel-sided ( Fig. 30 ). This is not at all similar to the distinct median lobe of the aedeagus of G. ovatus which is shorter than the parameres and has a peculiar leaf-like process at its apex ( Fig. 29 ). The gonocoxae also differ strongly between the two species, as those of G. sabanensis sp. nov. ( Fig. 56 ) are much more elongate, compared to the short, truncate gonocoxae of G. ovatus ( Fig. 53 ).

Etymology. This species is named for the region in which it was discovered, the Gran Sabana; adjective.

Habitat. This species is known from stream and river margin habitats ( Fig. 69 ).

Distribution. This species is currently only known from the type locality in the Gran Sabana of southeastern Venezuela ( Fig. 75 ).

Discussion. This new species is known from relatively high elevation streams within the Gran Sabana of southeastern Venezuela. Due to the limited number of specimens available, they were not destructively treated for SEM imaging.

Figures

Figs 1–6. Dorsal habitus of Neogyrinus species, scale bar = 1 mm. 1 – Gyrinus sabanensis sp. nov. 2 – G. gibbus Aubé, 1838 from Amazonian Venezuela. 3 – G. ovatus Aubé, 1838. 4 – G. guianus Ochs, 1935. 5 – G. gibbus ‘var. apicalis’ Sharp, 1877 from Caracas valley, Venezuela. 6 – G. rozei Ochs, 1953.

Figs 29–33. Dorsal and lateral view of the aedeagus of Neogyrinus species, not to scale. 29 – G. ovatus Aubé, 1838. 30 – G. sabanensis sp. nov. 31 – G. guianus Ochs, 1935. 32 – G. rozei Ochs, 1953.

Figs 51–59. Ventral view of gonocoxae of Venezuelan Gyrinus species, not to scale. 51–56 – Neogyrinus species. 51 – G. gibbus Aubé, 1838 from Caracas valley, Venezuela (FMNH). 52 – G. gibbus from Amazonian Venezuela: Amazonas stream along Rio Sipapo (KBMC). 53 – G. ovatus Aubé, 1838 from Venezuela: Falcón: W. Curimagua, Blackwater Lagoon.54 – G. guianus Ochs, 1935 from Amazonian Venezuela:Amazonas:river near Orinoco /Sipapo confluence (KBMC). 55 – G. rozei Ochs, 1953. 56 – G. sabanensis sp. nov. 57–59 – Oreogyrinus species: 57 – G. iridinus sp. nov. 58 – G. venezolensis Ochs, 1953. 59 – G. vinolentus sp. nov.

Figs 68–71. Habitat of Gyrinus species in the Guiana Shield region of Venezuela. 68 – Bolívar State, Gran Sabana, collecting event AS-08-063, habitat of G. rozei Ochs, 1953. 69 – Bolívar State, Gran Sabana, collecting event AS- 08-066, habitat of G. sabanensis sp. nov. 70 – Amazonas, tributary of the Rio Sipapo, collecting event VZ09-0116- 02X, habitat of G. guianus Ochs, 1935 and G. gibbus Aubé, 1838. 71 – Bolívar State, 25 km E. El Burro, collecting event AS-08-077, habitat of G. gibbus.

Figs 72–75. Distribution maps of Gyrinus species within Venezuela.