Gyrinus (Neogyrinus) rozei Ochs, 1953

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 : 497-499

Gyrinus (Neogyrinus) rozei Ochs, 1953

( Figs 6 , 24 , 27–28 , 32 , 55 , 68 , 73 , 79 )

Gyrinus (Neogyrinus) rozei Ochs, 1953: 186 (original description).

Type locality. ‘Espino, Est. Guárico’ [ Venezuela].

Type material examined. PARATYPE: J ( Fig. 79 ), ‘J [beige label, typed black ink]’ ‘ESPINO, GUÁR. / 28.3.1950 / RACENIS leg. [beige label handwritten in pencil]’ ‘R: 43 [beige label, typed black ink]’ ‘Coll. / G.Ochs [white label, typed black ink] ‘Para- / typoid / SMC C 9259 [red label, black border, typed black ink]’ ‘Senckenberg- / Museum / Frankfurt / Main [white label, typed black ink]’ ‘ rozei Ochs [beige label, handwritten, blue ink, handwriting Ochs’]’ ( SMF).

Other material examined. VENEZUELA: AMAZONAS: nr Iboruwa, ‘ Tobogancito’ , 5°48.414’N, 67°26.313’W, 13.i.2009, leg. Short & Miller,VZ 09011302 (1 spec. KBMC) . BOLÍVAR: Eof Kavanaven , 5°44’28.7”N, 61°30’54.3’W, 1290 m, 1.viii.2008, leg. Short & García, large vegetated marsh, AS-08-063, SM0829943, SM0829938 (2 spec. SEMC, MIZA) ; nr Rio Sakaika , 5°34’29.8”N, 61°18’43.4”W, 1100 m, 2.viii.2008, leg. Short & García, roadside pond, AS-08-067, SM0829320 (1 spec. KSM) . GUÁRICO: San Nicolasito Field Station , 8°8.296’N, 66°24.459’W, 10.i.2009, leg. Short & Miller, Morichal, VZ 09011002 (2 spec. KBMC) .

Diagnosis. Body form ( Fig. 6 ) narrowly oval, weakly convex in lateral view; pronotal and elytral margins broad, lighter in color, often yellow; elytral disc with mostly uniform reticulation, bronzy-metallic in appearance; striae II–XI ( Fig. 24 ) evident with distinct punctures, striae VI–IX sulcate; elytral intervals all evenly convex; elytral apex obliquely truncate ( Fig. 24 ), complete border faintly evident, epipleural angle distinct, never with denticle; metanepisternal ostiole absent; aedeagus ( Fig. 32 ) with median lobe nearly as long as parameres, broad, apex truncate; gonocoxae ( Fig. 55 ) short, apices strongly emarginate, medial angle strongly pointed.

Gyrinus rozei is most similar to G. guianus but can be distinguished from the latter by having the elytral striae much more apparent, with striae II–XI easily evident ( Fig. 24 ), compared to VI–XI in G. guianus ( Fig. 22 ). Gyrinus rozei can further be distinguished from G. guianus in having the striae composed of distinct round punctures ( Fig. 28 ), compared to the lineate punctures of G. guianus ( Fig. 26 ). Finally, the aedeagus differs drastically between the two species, in G. rozei the median lobe is exceptionally broad (wider than a paramere) and the apex is strongly truncate ( Fig. 33 ), compared to G. guianus which possesses a narrow median lobe with a strongly triangular apex ( Fig. 32 ). The gonocoxae of G. rozei are very unique among the Venezuelan Gyrinus species ( Fig. 55 ) having strongly emarginate apices with a strongly pointed medial angle.

Description. Size. Length = 3.5–4.0 mm, width = 2.0– 2.5 mm. Habitus. Bodyform narrowly oval, strongly attenuated anteriorly and posteriorly, widest point at midlength; in lateral view weakly dorsoventrally convex, greatest convexity posterior to scutellar region, evenly depressed anteriorly and posteriorly.

Coloration ( Fig. 6 ). Dorsally, head, pronotum, elytra bronzy-green, lateral margins of pronotum often yellow, some specimens reddish, others similarly colored as remainder of pronotum, elytral margins normally lighter in color, often yellow; 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. Pronotum with broad lateral margins. Elytra with stria Iweakly present, evident as reticulate stripes with variously developed sparse, weakly impressed punctures; striae II–XI ( Figs 24 ) evident, II–V ( Fig. 27 ) beginning with sparse weakly impressed punctures becoming progressively larger, more well impressed, and evenly distributed as strial number increases; stria VI weakly sulcate; striae VII–IX sulcate, with distinct round punctures ( Fig. 28 ); stria X non-sulcate, with slightly smaller and less impressed punctures basally and apically; stria XI raised above lateral margin for entirety. Elytral disc with mostly uniform reticulation composed of strongly impressed meshes with round sculpticells ( Figs 27–28 ), producing a bronzed appearance; all elytral intervals evenly convex. Elytra without medial pre-apical plica; apices obliquely truncate; border complete, faintly evident normally ( Fig. 24 ); epipleural angle prominent, never with small denticle. Metanepisternal ostiole absent. Ultimate abdominal tergite acute medially, but without strong acumination.

Male genitalia ( Fig. 32 ). Aedeagus with median lobe broad, about as long as parameres, parallel-sided basally, gradually laterally expanded in apical 1/3, apex strongly truncate, bifid, with medial pair of denticles; parameres with apex truncate. Female genitalia ( Fig. 55 ). Gonocoxae short, apices strongly emarginate, medial angle strongly pointed, left gonocoxa more so than right.

Variability. Specimens from Bolívar, Venezuela had more well impressed elytral reticulation, giving them a much more grainy and metallic appearance. The appearance of the elytral striae also varied considerably. The specimen from Amazonas had theelytral striae more weakly impressed and less sulcate in appearance compared to other specimens. Those from Bolívar had the most strongly impressed and sulcate appearing elytral striae. This resulted in somewhat more convex associated elytral intervals compared to both the Amazonas and Guárico specimens.

Habitat. In Venezuela this species has been largely collected within lentic habitats ( Fig. 68 ).

Distribution. Known from the llanos and Guiana shield regions of Venezuela ( Fig. 73 ).

Discussion. This species is currently only known from Venezuela. Given its distribution spreads across southern Venezuela ( Fig. 73 ) it is likely more widely spread in the Guiana shield, similar to G. guianus .

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 22–24. 22–23 – SEM images of G. guianus Ochs, 1935 elytral morphology. 22 – elytron, box indicates region shown in Fig. 23, scale bar = 1 mm. 23 – elytral apex, arrow indicates medial pre-apical plica. 24 – elytron of G. rozei Ochs, 1953, scale bar = 1 mm.

Figs 25–28. SEM images of elytral interval reticulation and strial punctures. 25–26 – G. guianus Ochs, 1935. 25 – intervals II and III, striae I–III. 26 – intervals IX and X, striae VIII–X. 27–28 – G. rozei Ochs, 1953. 27 – intervals II and III, striae I–III. 28 – intervals IX and X, striae VIII–X.

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.

Figs 76–81. Type specimens and associated labels. 76 – Gyrinus amazonicus Ochs, 1958, paratype male (BMNH). 77 – G. guianus Ochs, 1935, holotype female (BMNH). 78 – G. racenisi Ochs, 1953, paratype female (SMF). 79 – G. rozei Ochs, 1953, paratype male (SMF). 80 – G. venezolensis Ochs, 1953, paratypes, male and female (SMF). 81 – G. opalinus Régimbart, 1883, syntype male and labels (MNHN).