Hydrolutos breweri Derka & Fedor

Derka, Tomáš & Fedor, Peter, 2010, Hydrolutos breweri sp. n., a new aquatic Lutosini species (Orthoptera: Anostostomatidae) from Churí-tepui (Chimantá Massif, Venezuela), Zootaxa 2653, pp. 51-59 : 53-58

Hydrolutos breweri Derka & Fedor sp. nov.

Description. Male.

Colour and markings: Body dark brown. Head capsule, including mandibles, dark brown with a bright belt-like pattern on vertex and 3 bright spots triangularly situated on frons, shiny and almost smooth, eyes black. Palpi light basally and distally, with dark middle section. Thorax and abdomen very dark brown dorsally, with light bands on terga (light area on pronotum). Legs brighter than body ( Fig. 2, 3).

Head: Antennal flagellum about 2.5 times total body length, proximally smooth, in middle and distal section swollen and covered by short fine microsetae. Fastigium as broad as antennal segment S1, horizontal, slightly flattened, not declinate, with a median carina. Vertex convex, clypeus subtriangular with indistinct median carina. Labrum heart-shaped, proximally broader than distally, with median carina in its apical half. Maxillary palps bright, the last segment swollen and covered by short fine and soft microsetae. Eyes elevated in frontal view ( Fig. 4 ).

Thorax: Pronotum slightly elevated over mesonotum, as long as wide, bordered by a smooth rolled margin, containing both smooth and gently rugose areas. All thoracic sterna with 2 spines, prosternum: 2 moderate spines posterolaterally elevated, mesosternum: 2 spines posterolaterally elevated, metasternum: 2 distinct spines with no lateral elevation ( Fig. 2, 3).

Legs long, forecoxa with a moderate lateral spine, midcoxa with a short blunt spine, femora without spines. Fore tibiae dorsally with 2 spines subapically and 2 apically, ventrally with 2 rows of 5 spines (including the apical ones). Middle tibiae dorsally with a row of 4 spines on internal side and a row of 3 spines on external side, ventrally with 2 rows of 5 spines. Hind tibiae with 2 lateral combs of short but firm spines, ventrally with 2 moderate subterminal and 2 superior terminal spines. Tympanum elypsoid, dark brown.

Abdomen: Abdominal apex and genitalia as on Figures 5 , 6 , 7 . Abdominal tergites smooth with fine transverse striae mesally and with posterior edges darker. Genitalia pubescent. Supra-anal plate bilobulate terminally slightly curved upwards. Cerci cylindrical, rugose, directed gently upwards, with blunt apices and without internal processes. Subgenital plate as long as wide, very gently concave laterally, without any emargination between styles, with flat posterior margin and long styli directed ventrad.

Measurements. Body length 43.2 mm (including cerci 47.1), fastigium width 1.2 mm, interocular space 5 mm, pronotum length 9.9 mm, width 11.1 mm, hind femur length 35.5, width (7 mm max.), (2 mm min.), hind tibia length 35.5 mm, hind tarsus length 11.3 mm, hind tarsi length: I 4.1 mm, II 3.0 mm, III 2.1 mm, IV 1.5 mm, abdomen length (without cerci) 22.4 mm.

Female. Unknown.

Material examined. Holotype. 1 ɗ body length 43.2 mm, Venezuela, Edo. Bolívar, Chimantá Massif, Churí tepui, Cueva Charles Brewer, ca 2300 m a.s.l., 15.I. 2009. Holotype has been preserved dry and pinned.

Paratypes. ɗ body length 43 mm, 1 Ψ nymph, body length 30 mm. The same data as holotype. The paratypes are stored in 70% ethanol. Holotype and paratypes will be deposited in Museo del Instituto de Zoología Agrícola ( MIZA), Facultad de Agronomía, Universidad Central de Venezuela, Maracay, Edo. Aragua, Venezuela.

Etymology. Species named in honour of Charles Brewer-Carías, in recognition of his great contribution to exploration of Venezuelan Guyana. He has led over 200 expeditions in Venezuelan Guyana Highlands. His most famous discoveries are in geological features in the tepuis such as the giant sink holes on Sarisariñama, the world’s largest quartzite cave on Churí-tepui and many other previously unexplored caves.

Ecology. As other members of the genus, H. breweri inhabits aquatic habitats. Numerous individuals were observed walking and swimming inside the stream and walking outside the water at the bottom and walls of the Cueva Charles Brewer ( Fig. 8 ). Thanks to high ability to cling by means of strong legs and tarsal claws it is able to move even against strong current. Because of permanent darkness in the cave, individuals were observed active 24 hours, not only during the night as it was reported for other members of the genus ( Issa & Iaffe 1999, pers. observ.). However, it can not be considered troglobiont because of lack of typical adaptations (e.g. reduction of eyes and coloration), and the occurrence of this species can be expected in other streams at Churí-tepui plateau outside the Cueva Charles Brewer.

Diagnosis. The species is easily distinguished on a few characters. Clypeus triangular (subtriangular in H. chimantea ), laterally more distinct than in H. ayuan . Palpi bright but dark in H. aracamuni . Labrum heartshaped, but oval in H. raraimae and H. auyan . Fastigium as broad as antennal segment I, but broader in H. roraimae and H. aracamuni . Epiproct bilobulate terminally, but oval in H. aracamuni . H. breweri is unique among other members of the genus by extremely long hind tibiae reaching length of hind femur. In remnant Hydrolutos species hind femur is always longer then hind tibia.

Figures

FIGURE 4. Head of male Hydrolutos breweri sp. n. — a frontal view (photographed by C. Brewer-Carías).

FIGURE 5. Genitalia of male Hydrolutos breweri sp. n. — a dorsal view.

FIGURE 6. Genitalia of male Hydrolutos breweri sp. n. — a lateral view.

FIGURE 7. Genitalia of male Hydrolutos breweri sp. n. — a ventral view.

FIGURE 8. Male Hydrolutos breweri sp. n. in its natural habitat.