Oocyclus petra Short & García, 2010

Short, Andrew E. Z. & García, Mauricio, 2010, A review of the Oocyclus Sharp of Venezuela with description of twelve new species (Coleoptera: Hydrophilidae: Laccobiini), Zootaxa 2635, pp. 1-31 : 18-20

Oocyclus petra Short & García sp. n.

( Figs. 4 A, 6A, 7, 10)

Type material. Holotype: VENEZUELA: Amazonas State: male, “ VENEZUELA: Amazonas State/ 5°23.207’N, 67°36.922’W, 125 m / Tobogan de la Selva; 14.i.2009 / leg. Short, García, Miller, & Joly/ wet rock covered w/ detritus/ VZ09-0114-01F; upstream slide”, “[barcode]/ SEMC 0853777/ KUNHM-ENT”, “ HOLOTYPE / OOCYCLUS / petra sp.n. / des. Short & García 2010 ” ( MIZA). Paratypes (1279 exs.): VENEZUELA: Amazonas State: Tobogan de la Selva: 19.ii.1986, leg. P.J. Spangler, collection #1 (84 exs., USNM); 22.ii.1986, leg. P.J. Spangler, collection #6 (361 exs., USNM); 22.ii.1986, leg. P.J. Spangler, side arm of stream, collection #7 (8 exs., USNM); 22.ii.1986, leg. P.J. Spangler, edge of lower falls, “bare rock streambed in sunlight; beneath wet leaves at margin” collection #9 (21 exs., USNM); 23.ii.1986, leg. P.J. Spangler, sandy margins, collection #10 (11 exs., USNM); 24.ii.1986, leg. P.J. Spangler, collection #13 (1 ex., USNM); 24.ii.1986, leg. P.J. Spangler, in potholes, collection #13: (4 exs., USNM); 25.ii.1986, leg. P.J. Spangler, collection #15 (6 exs., USNM); 25.ii.1986, leg. P.J. Spangler, leaves from stream, collection #16 (84 exs., USNM); 25.i.1989, upper seep, leg. P.J. Spangler, R.A. Faitoute, & C.B. Barr (1 ex., USNM); 26.i.1989, P.J. Spangler, R.A. Faitoute, & C.B. Barr, seep at upper shelter (41 exs., USNM); Tobogan: 4.viii.1992, (1 ex., MIZA); Tobogan: 5.i.2006, leg. A. Short & P. Torres, sandy margin of stream, AS-06-011a (6 exs.); Tobogan: 5.i.2006, leg. A. Short, rock pools/wet leaves, AS-06-011c (27 exs.); Tobogan: 5.i.2006, leg. A. Short & P. Torres, wet rock with leaves and detritus, AS-06-011e (197 exs.); 7.i.2006, leg. A. Short, AS-06-017 (2 exs.); 12.ix.2007, leg. A. Short, M. García, L. Joly, washing main slide, AS-07-007b (8 exs.); Tobogan: 24.i.2004, leg. M. García (13 exs.); 14.i.2009, leg. Short, Miller, & Joly, margin of mail slide, VZ09-0114-01A (8 exs.); 14.i.2009, leg. A. Short, clumps of wet leaves on rock, VZ09-0114-01D (5 exs); same data as holotype (83 exs.); other localities in Amazonas State: 35 km SE Puerto Ayacucho, Gavilan area, 20.ii.1986, leg. P.J. Spangler & W. Sanchez, in masses of foam, collection #3 (20 exs., USNM); 37 km SE Puerto Ayacucho, Rio Gavilan, 20.ii.1986, leg. P.J. Spangler & W. Sanchez, collection #2 (3 exs., USNM); ca. 15 km S. Puerto Ayacucho, nr. Campamento Canturama, 5°30.623'N, 67°36.109'W, 100 m, isolated seepage on side of rock outcrop, leg. A. Short & M. García, AS-07-009a (34 exs.); same locality but 14.ix.2007, leg. A. Short & M. García, AS-07-011X (4 exs.); between Puerto Ayacucho & Samariapo, small stream in road culvert, 6.i.2009, AS-06-013 (7 exs.); between Puerto Ayacucho & Gavilan, 5°32.803', 67°26.924'W, 77 m, small stream, 6.i.2009, leg. A. Short, AS-06-014 (13 exs.); between Puerto Ayacucho & Gavilan, 5°34.408'N, 67°30.283'W, 66 m, 6.i.2006, small stream, leg. A. Short, AS-06-015 (24 exs.); Communidad Caño Gato on Rio Sipapo, 7.i.2006, leg. A. Short & P. Torres, AS-06-016 (1 ex.); S. Puerto Ayacucho, Campamento Nacamtur, isolated rock seepage on outcrop, 14.ix.2007, leg. A. Short, AS-07-013X (68 exs.); Nr. Iboruwa, 5°48.414'N, 67°26.313'W, 80 m,“Tobogancito”, rock pool with detritus, 13.i.2009, leg. A. Short, VZ09-0113-02B (2 exs.); same data but VZ09-0113- 02X (5 exs.); River near confluence of Orinoco & Sipapo rivers, 5°03.707'N, 67°46.768'W, shallow backwaters on rock, 15.i.2009, 92 m, leg. A. Short, VZ09-0115-01C (5 exs.); 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.); W. Communidad La Danta, 5°34.512'N, 67°32.498'W, 80 m, kick netting, 15.i.2009, leg. Short & Camacho, VZ09-0115-04A (2 exs.); Stream along Rio Sipapo, 4°55.849'N, 67°44.645'W, 87 m, 16.i.2009, leg. Short, García, Camacho, Miller, & Joly, VZ09-0116- 02X (1 ex.); Bolívar State: Los Pijiguaos, 6°35.617'N, 66°49.238'W, 80 m, outcrop/morichal, marginal algae on rock, 12.i.2009, leg. Short, García, Camacho, Miller, & Joly, VZ09-0112-01B (16 exs.); same locality but leg. A. Short & M. García, 16.ix.2007, AS-07-015 (44 exs.); Rio Caripito, 6.58694°N, 67.02912°W, detrital pool, 12.i.2009, leg. A. Short & K. Miller, VZ09-0112-02B (1 ex.); ca. 25 km E. El Burro, 06°13.059'N, 67°14.467'W, 62 m, 15.ix.2007, leg. A. Short, AS-07-013 (2 exs.); same locality but 13.i.2009, leg. Short, García, Camacho, Miller, Joly, VZ09-0113- 01C (11 exs.); same date and locality but VZ09-0113- 01X (2 exs.); 5.viii.2008, ca. 14 km E Rio Aro, 7°41'23.6"N, 64°1'56.0"W, 134 m, rock outcropping, leg. A. Short, AS-08-073 (3 exs.); 2 km E. Cuchivero, 7°29'47.3"N, 65°51'44.8"W, 45 m, 6.viii.2008, leg. A. Short, M. García, & L. Joly, AS-08-075 (38 exs.).

Additional material examined: VENEZUELA: Bolívar State: Auyantepui, Camp A, 10–13.ii.1988, 2100 m, leg. L. Joly & A. Chacon (1 ex., MIZA), Ayantepui, 1650 m, 26.viii.1992, C.G. Trezzi (1 ex., MIZA).

Diagnosis. Larger species ( Fig. 4 A). Posterolateral corners of pronotum strongly spinose. Procoxae spinose. Elytra without rows of larger systematic or serial punctures. Elytral suture not raised in posterior third. Elytral margins not explanate, and without a marginal fringe of long setae. Ground elytral punctation bearing short setae. Elytra with mottled white patches along posterior margin of elytra.

This species may be distinguished from all other Venezuelan species by the short, fine setae of the ground punctation and the white marginal maculae on the elytra. The latter character is quite variable, and some dark specimens may appear to lack this feature. It is not strongly similar to any other Venezuelan Oocyclus species.

Description. Size and form. Body length = 3.7–5.3 mm (most specimens 4.0–5.0 mm). TL/GW= 1.7. Body oval, moderately convex.

Color. Dorsum of head, pronotum, and elytral disc black with general faint iridescent green sheen. Anterolateral margins of pronotum broadly margined pale yellow on anterior two-thirds. Elytra without distinct iridescent maculae, however the iridescent sheen may be irregularly distributed, giving the appearance of subtle patches; posterior two-fifths of elytra along lateral margin with depigmented (translucent) region, giving the elytra yellow margined appearance. Maxillary and labial palps yellow. Mentum and stipes dark brown, not distinctly paler than ventral face of head. Legs, epipleura, lateral margins of prosternum yellowish brown. Abdominal ventrites dark brown with pale patches laterally on ventrites 1–4.

Head. Ground punctation on labrum, clypeus and frons distinctly impressed, distance between punctures 1.5–3.0× the width of one puncture. Systematic punctures on labrum consisting of several indistinct punctures medially. Frons with irregular row of systematic punctures mesad of each eye, bearing fine erect setae. Clypeus with a few very indistinct systematic punctures along anterolateral margins, slightly larger than surrounding punctation. Some ground punctures on head bearing minute setae. Maxillary palps short, about as long as width of labrum; segment 2 slightly bulbous, apical segment slightly longer than penultimate. Labial palps three-fourths as long as width of mentum. Mentum quadrate, anterior margin convex, bearing fine punctures.

Thorax. Ground punctation on pronotum and elytra composed of distinct evenly distributed punctures of generally uniform size with very short, slightly thickened setae. Pronotal systematic punctures with short fine setae, similar to slightly larger in size to ground punctures, blending with larger ground punctures. Lateral margins of pronotum with short indistinct setae; margins of elytra with row of very short coarse spine-like spicules. Posterolateral corners of pronotum weakly to sharply spinose. Sutural punctation on elytra absent or unmodified from ground punctation. Elytra without distinct rows of larger systematic punctures, as they blend uniformly with ground punctation. Prosternum with strongly raised median carina elevated anteromedially, the elevation with two thick spine-like setae. Elevated process of mesoventrite narrow and elongate, more than twice as long as wide; with 5–6 thickened, coarse spine-like setae. Metaventrite with long, narrow glabrous area posteromedially, more than twice as long as wide, length of glabrous area more than two-thirds the length of the metaventrite. Procoxae with dense, fine short pubescence, and throughout with long, coarse spine-like setae. Protibiae each with 6 spine-like setae on dorsal face.

Abdomen. Ventrites with scattered setae of varying length; each ventrite with irregular rows of long erect setae which are more than twice as long as the longest setae on metaventrite. Aedeagus as in Figure 6 A.

Variation. This species has the largest size variation among all species examined here. Even a single population may have individuals at opposite ends of this variation; it is not correlated with geography or time of year. The white margin and spots at the apex of the elytra is nearly always present but varies it its contrast with the surrounding dark coloration; in some specimens the spots are very darkened and thus may appear absent unless carefully examined.

We examined two female specimens from Ayantepui, many hundreds of kilometers to the east of the rest of the known populations, that we tentatively assign to this species but which we did not include as paratypes. These specimens agree in many aspects with the ‘typical’ O. petra specimens, but are the largest known examples, and have a much broader pale pronotal anterolateral margin. While these characters of size and color are often very variable within species (including O. petra ), the fact that these two specimens were collected from different sites and times on the tepui, and yet still share the same outlying features, suggest that perhaps they may represent a distinct species. This possibility is further enhanced by geographic separation from other collecting events. More specimens, including males, are needed before a final determination can be made.

Etymology. Petra , a latinized Greek noun for a large rock. Used as a noun in apposition.

Distribution. Found in southern Venezuela (States of Amazonas and Bolívar), along the northwestern edge of the Guiana Shield ( Fig. 7 ).

Remarks. Within its range, O. petra is frequently encountered in nearly all seepage habitats, sometimes in exceedingly large numbers (e.g. Fig. 10 ). This is evidenced by the fact that well over 1000 specimens have been examined, including several series of hundreds of individuals. On more than one occasion in the dry season, so many individuals were observed on riparian rock seepages covered with fallen leaves that we simply could not have collected them all even if we had desired. Found in both wet and dry seasons, it is found in a variety of hygropetric habitats, including wet rock adjacent to streams as well as isolated, temporary seeps ( Fig. 10 A) that are hundreds of meters from the nearest permanent water source suggesting they may disperse with relative ease.

Of particular interest is that this species is one of the few (and perhaps only known) that occurs in streams that are not associated with hygropetric habitats. It is not uncommon to find the species (albeit, not the aforementioned large numbers) in sandy/detrital margins of regional streams.

Figures

FIGURE 4. Dorsal and lateral habitus of Oocyclus species found in the Venezuelan Guiana Shield region. A) O. petra sp. n., B) O. coromoto sp. n.; C) O. floccus sp. n. Scale bar = 2.0 mm.

FIGURE 6. Aedeagi of Oocyclus species. A) O. petra sp. n., B) O. galbus sp. n.; C) O. pico sp. n. D) O. bolivari sp. n. Scale bar = 0.2 mm.

FIGURE 7. Distribution of Oocyclus species in Venezuela.

FIGURE 10. Habitat of Oocyclus species. A) Amazonas State, 15 km S. Puerto Ayacucho, collecting event AS- 07 - 009 a; locality and habitat of O. petra. B) Amazonas State, Tobogan de la Selva; habitat for O. petra. C) Amazonas State, Tobogan de la Selva, habitat for O. petra and O. coromoto.