Oecobius thar, Tripathi & Sudhikumar & Sherwood, 2023

Tripathi, Rishikesh, Sudhikumar, Ambalaparambil V. & Sherwood, Danniella, 2023, A new species of Oecobius Lucas, 1846 from the Thar Desert, India (Araneae: Oecobiidae), Zootaxa 5389 (4), pp. 483-490 : 485-488

Oecobius thar sp. nov.

Figs 1–5

Etymology. The specific name refers to the Thar Desert, where this species lives, and is a noun in apposition.

Type material. Holotype ♂ (NRC-AA-4153), INDIA: Rajasthan, Jaisalmer, Thar Desert, Sam area (26.8303°N, 70.5085°E). 235 m a.s.l., found on wall, collected by hand, 14 Aug. 2022, R. Tripathi coll. Paratypes: same data as holotype, ♂ (NRC-AA-4154), ♀ (NRC-AA-4155) .

Diagnosis. Oecobius thar sp. nov. most closely resembles O. cumbrecita Wunderlich, 1987 , O. fortaleza Wunderlich, 1992 and O. infierno Wunderlich, 1987 by the curved OTL ( Figs 2A–C , 3 ), however it can be distinguished by the apex of the OTL ending with three denticles ( Figs 2B–C ), which are absent in O. cumbrecita , O. fortaleza and O. infierno . Females of O. thar sp. nov. can be distinguished by the triangle-shaped and heavily sclerotised epigyne ( Fig. 2D , not triangle-shaped in all other known congeners).

Description. Male holotype: Colour (in alcohol): carapace and dorsal and lateral faces of palp dark brown; legs beige, with black annulation on all segments; opisthosoma overall dark brown (darker than carapace), dorso-lateral outermost quarters mottled with white blotches, dorso-medial area with foliate pattern at posterior extent, spinnerets and ventral face of the opisthosoma dark brown ( Fig. 1A–B ). Total length 1.77. Carapace 0.75 long, 0.82 wide. Eyes: ALE 0.04, AME 0.06, PLE 0.08, PME 0.02, ALE–ALE 0.16, AME–AME 0.06, PLE–PLE 0.11, PME–PME 0.04. Opisthosoma 1.02 long, 0.68 wide. Legs: I 2.24 (0.68+0.13+0.50+0.51+0.42), II 2.51 (0.73+0.15+0.57+0.61 +0.45), III 2.55 (0.74+0.18+0.55+0.62+0.46), IV 2.69 (0.76+0.22+0.59+0.63+0.49). Palp: with massive oecobiid tegular lobe tapering strongly in proximal third, apex with three denticles, process present at base; embolus short; oecobiid tegular apophysis well-developed with two projections at apex, base with proximal process; membranous conductor present and rounded, anterior part of tegulum smooth and unmodified ( Figs 2A–C , 3 ).

Female paratype: Colour (in alcohol): carapace dark brown; legs beige and non-annulated; opisthosoma overall beige, overlain with black setae, dorso-median aspect with foliate pattern and two parallel black blotches, spinnerets and ventral face of opisthosoma mouse brown ( Fig. 1C–D ). Total length 1.89. Carapace 0.66 long, 0.72 wide. Eyes: ALE 0.04, AME 0.06 PLE 0.07, PME 0.03, ALE–ALE 0.16, AME–AME 0.07, PLE–PLE 0.14, PME–PME 0.03. Opisthosoma 1.23 long, 0.79 wide. Legs: I 2.12 (0.67+0.14+0.48+0.43+0.40), II 2.36 (0.72+0.16+0.55+0.51+0.42), III 2.43 (0.75+0.19+0.51+0.57+0.41), IV 2.71 (0.71+0.22+0.63+0.75+0.40). Genitalia: epigyne triangle-shaped, sclerotised, with prominent proximal apex and widely spaced copulatory openings; copulatory atrium prominent, copulatory ducts twisted, each with an anterior diversion in the proximal third, copulatory ducts connecting at apex to asymmetrical globular spermathecae ( Figs 2D–E ). We were unable to observe any fertilisation ducts, although cannot rule out their presence.

Colour in vivo. Typically as found in the (freshly) preserved specimens, although both male ( Fig. 4A–C ) and female ( Fig. 4D ) are more vibrant in respective colours.

Natural history. Oecobius thar sp. nov. exhibited a habitat preference consistent with a synanthropic lifestyle ( Fig. 4E ). A large number of specimens were observed by RT on a residential wall, where female specimens constructed small sheet webs housing a cluster of eggs. They were observed to primarily predate ants and dipterans. During prey capture, the females employed a dynamic strategy, swiftly manoeuvring around their prey and utilizing a continuous silk-spinning technique to entrap and immobilize the target (RT pers. obs.). This behaviour is in no way unique, having been reported in several other congeners ( Glatz 1967; Voss et al. 2007; García et al. 2014; Líznarová et al. 2013; Líznarová & Pekár 2015).

Distribution. Known only from the type locality, in the Thar Desert ( Fig. 5 ).

Figures

FIGURE 1. Oecobius thar sp. nov. holotype male (A–B) and paratype female (C–D), A male, habitus, dorsal view, B male, close-up of spinnerets, ventral view, C female, habitus, dorsal view, D female, close-up of spinnerets, ventral view. Scale bars = 0.5mm (A–C), 0.1mm (D).

FIGURE 2. Oecobius thar sp. nov. holotype male (A–C) and paratype female (D–E), genitalia, A male palp, prolateral view, B ibid, ventral view, C ibid, retrolateral view, D epigyne, ventral view, E vulva, dorsal view. Scale bars = 0.2mm. Abbreviations: AP = process on the oecobid tegular apophysis, CA = copulatory atrium, CD = copulatory ducts, CO = copulatory openings, CON = conductor, E = embolus, LP = process on the oecobiid tegular lobe, OTA = oecobiid tegular apophysis, OTL = oecobiid tegular lobe, S = spermathecae.

FIGURE 3. Oecobius thar sp. nov. holotype male, palp under Scanning Electron Microscope, A retro-ventral view, B prolateral view. Scale bars = 1mm (B), 0.5mm (A).Abbreviations:AP = process on the oecobiid tegular apophysis, CON = conductor, E = embolus, LP = process on the oecobiid tegular lobe, OTA = oecobiid tegular apophysis, OTL = oecobiid tegular lobe.

FIGURE 4. Oecobius thar sp. nov. habitus in vivo and type locality, (A–C) holotype male, D paratype female, E habitat at type locality. Photo credit. Rishikesh Tripathi.

FIGURE 5. Type locality of Oecobius thar sp. nov. (circle), A general view of location in India, B satellite imagery of type locality, showing desert habitat, C Thar Desert ecoregion (in pink) in relation to other nearby ecoregions.