Sason rameshwaram, Siliwal, Manju & Molur, Sanjay, 2009

Siliwal, Manju & Molur, Sanjay, 2009, A new species of the genus Sason (Araneae: Barychelidae) from Rameshwaram Island, Tamil Nadu, India, Zootaxa 2283, pp. 60-68 : 62-67

Sason rameshwaram sp. nov.

Figs 2–34

Type data: India— Holotype, female, 6.x.2005, on tamarind tree close to Petrol Bunk next to bus stop, 9°17’05.0”N, 79°17’41.2”E, elevation 1m, Rameshwaram Island, Tamil Nadu, coll. Manju Siliwal and B. Ravichandran, WILD –05–ARA–88. Allotype, male, 26–viii–2006, Hanumavilasum Temple site, 9°07’32.1”N, 79°16 28.5”E, elevation 17m, Ariyagundur, Rameshwaram Island, Tamil Nadu, coll. Manju Siliwal and B. Ravichandran, WILD –06–ARA–153. Paratype, 1 female, 1–x–2005, same data as allotype, WILD –05–ARA–87.

Diagnosis: S. rameshwaram , closely resembles S. sundaicum in the number of cuspules on labium and maxillae in male and female (number of cuspules in S. rameshwaram falls within the range of S. sundaicum ), bare paired claws on legs of males and females; single claw with three teeth on female palp; scopula on tarsi IV indistinct or rudimentary in females.

The female of S. rameshwaram differs from all the known species of Sason by the spermathecal structure having multilobed apex, from S. robustum and S. cinctipes by the absence of teeth on the paired claws of all legs and presence of 3–5 teeth on the palpal claw; differs further from S. robustum by the presence of thin scopulae on metatarsus III and tarsus IV; differs from S. sundaicum by presence of few distal scopuliform hairs on metatarsi III and scopula divided by scattered setae on tarsi IV, rastellam structure (in S. sundaicum , it is a single spinule associated with 1–2 thick setae and in S. rameshwaram , there is only single spinule resembling setae).

The male of S. rameshwaram differs from all the known males in palp structure (roughly spheroidal, with dorsal depression in the center); apart from this it differs from S. robustum and S. andamanicum by having 8 pointed thin cuspules on labium, the presence of two basomesal teeth on furrow of chelicerae and the palpal embolus slender and gently curved, evenly narrowed down gradually towards tip (in S. robustum , the embolus is straight, narrow and tapering; S. andamanicum , embolus base is wide and abruptly narrowing beyond the proximal third); it differs from S. robustum by bare paired claws on all the legs, palp embolus slightly curved (in S. robustum its straight); it differs from S. sundaicum by scopula on tarsi III (indistinct in S. sundaicum and divided by setal band in S. rameshwaram ), scopula on tarsi IV (present in distal portal of tarsi IV in S. sundaicum and in S. rameshwaram it is rudimentary and divided by scattered setae), rastellam structure (in the form of setae in S. sundaicum ; in the form of small coniform spicule in S. rameshwaram ); area near tibial spur pigmented (in S. sundaicum , large area distal to tibial spur glaborous and unpigmented), tibial spur carrying megaspine pointing away from tibia at almost acute angle (in S. sundaicum , it points at almost a right angle); palp embolus slightly curved (in S. sundaicum , the embolus is straight).

Etymology: The species epithet is a noun in apposition taken from the type locality, Rameshwaram Island.

Description: female holotype ( Figs 2–12 , 23–28 )

Colour in life ( Fig. 12 ): Carapace reddish-brown with black area near eyes, blackish bands towards the margins (indistinct in preserved specimen). Abdomen dorsally dark brown with large cream paired patches extending dorsolaterally and posteriorly; ventrally yellowish with small dark brown patches on lateral sides near book-lungs; legs yellow, black complete annulations on patellae and tibiae, black annulations on dorsal and lateral side of femora and patellae ( Fig. 9 ); sternum yellow. Colour in alcohol slightly paler/faded.

Measurements. Total length 11.20. Carapace 5.50 long, 5.00 wide; chelicerae 0.88 long. Legs (femur, patella, tibia, metatarsus, tarsus, total): I: 3.14, 2.62, 2.28, 2.14, 1.42, 11.60. II: 3.00, 2.62, 2.52, 2.00, 1.42, 11.56. III: 3.02, 2.34, 2.50, 2.00, 1.42, 11.28. IV: 4.0, 3.12, 3.22, 2.72, 1.48, 14.54. Palp: 2.72, 1.60, 1.76,–, 1.9, 7.98. Midwidths: femora I–IV, 1.56, 1.38, 1.28, 1.22; tibia I, III, IV=1.10, II=1.08. Abdomen 5.70 long, 4.60 wide.

Carapace ( Figs 3 , 23 ). Fovea not very deep, centrally placed, broad, transverse almost straight with recurved ends ( Fig. 3 ), thoracic area gradually sloping downwards posteriorly. Bristles: long and short bristles on caput; 5 long, thick anteromedian; 9 long and 5–6 short on clypeal edge; 3 long between AME, 3–4 long and 3 short between PME; absent on lateral margin but small hairs present; small bristles and several hairs along interstrial ridges.

Eyes ( Figs 3 , 24 ). ALE, AME and PLE on low tubercle; three rows; eye group width at its broadest / head width at same point, 0.41; eye group front width 1.60, back width 1.80, length 1.10; diameter of eyes: AME 0.60, ALE 0.50, PME 0.20, PLE 0.40; minimum eye interspace: AME–AME 0.60, AME–ALE 0.30, ALE– PLE 0.50, ALE–ALE 1.20, PME–PLE 0.10, PME–PME 1.00; MOQ: front width 1.1, back width 1.3, length 0.8.

Chelicerae ( Figs 6–7 , 25 ). Short, reddish-brown, two hairless bands lengthwise, several bristles present; rastellum consists of small single median spicule ( Fig. 6 ); six promarginal teeth, spaced; 3–4 small basomesal teeth in chelicerae furrow ( Figs 7 , 25 ).

Labium ( Figs 4 , 27 ). 0.80 long, 1.20 wide; separated from sternum by shallow labiosternal groove; eight strong pointed cuspules on anterior margin, three small, pointed incipient cuspules/spinules (two in centre, one lateral) behind larger cuspules.

Maxillae ( Figs 4 , 27 ). 1.80 long, 1.10 wide; with 6–7 cuspules on inner edge; thick bristles on entire ventral face, few long hairs on prolateral face, retrolateral face glabrous.

Sternum ( Figs 4 , 27 ). 3.54 long, 2.60 wide; gradually sloping anteriorly; uniformly covered with thick bristles, bristles also on margin; posterior sigilla oval, marginal, 1.60 from each other; median sigilla, round, marginal, 2.00 diameters from each other; anterior sigilla absent.

Legs ( Figs 9–11 ). Formula 4123. Two glabrous longitudinal bands on all femora, patellae and tibiae. Scopulae: lateral, ventral, distinct on metatarsi and tarsi I, II; few distal scopuliform hairs on metatarsi III; divided by scattered setae on tarsi III; absent on metatarsi IV; rudimentary on tarsi IV. Spines: Leg I: pa, v1; ti, v5. Leg II: pa, v1; ti, p1, v5. Leg III: ti, v3. Leg IV: 0. Palp: pa, v3; ti, v6. Metatarsi aspinose. Bristles: Leg I: fe, d9; Leg II: fe, d9, pa, v6; Leg III: fe, d6, me, v7, ta, d6; Leg IV: fe, d5; ti, v4, me, v6; Palp: fe, d9. Claw: paired claws bare ( Fig. 10 ); palp, single claw with 3–5 teeth ( Fig. 11 ), strong claw tufts present. Trichobothria: ca. 5–10 in distal ¾ of tibia I–II, ca. 8–13 in distal 2/3 of tibia III–IV; ca. 3–4 in distal third of metatarsi; 2–3 clavate (basal), 3–5 filiform on leg tarsi; palp tarsi with 7–8 clavate (basal) and 6–7 filiform in distal half.

Spinnerets ( Figs 8 , 26 ). Posterior median spinnerets digitiform, 0.40 long, 0.22 wide at midpoint, 0.20 apart; posterior lateral spinnerets 1.30 long (0.70 basal, 0.40 middle, 0.20 apical), dome-shaped.

Spermathecae ( Fig. 28 ). Genitalia simple, consisting of two widely separated spermathecae with multilobed apex and stem broader at base.

Variation. Total length 11.20–13.18. Carapace 5.42–5.50 long, 4.56–5.0 wide. Abdomen 5.70–7.76 long, 4.60–5.82 wide. 8–11 cuspules on labium and 4–7 cuspules on maxillae. Sternum 3.10–3.54 long, 2.42–2.60 wide. Morphometry of female paratype (WILD–06–ARA–87) legs (femur, patella, tibia, metatarsus, tarsus, total): I: 3.12, 2.72, 2.56, 1.78, 1.62, 11.80. II: 3.28, 1.62, 2.30, 1.68, 1.36, 10.24. III: 2.86, 1.58, 1.90, 1.86, 1.42, 9.62. IV: 3.50, 2.32, 3.0, 2.80, 1.48, 13.10. Palp: 2.64, 1.62, 1.68,–, 1.90, 7.84. Midwidths: femora I–IV, 1.30, 1.28, 1.26, 1.16; tibiae I, III, IV=1.0, II=0.98.

Description. Male allotype ( Figs 15–21 , 29–34 )

Colour in alcohol ( Fig. 19 ). Carapace yellowish-brown, with black area near eyes, dark brown radial marks, more obvious towards margins than in center. Chelicerae yellowish, with darker areas, two hairless bands running lengthwise dorsally. Abdomen dorsally dark brown, with large cream paired patches extending dorsolaterally and posteriorly; yellowish ventrally. Legs yellowish with black annulations.

Measurements. Total length 6.84. Carapace 3.02 long, 3.10 wide. Legs (femur, patella, tibia, metatarsus, tarsus, total): I: 3.16, 1.80, 2.60, 2.10, 1.20, 10.86. II: 3.20, 1.68, 2.56, 1.84, 1.20, 10.48. III: 3.20, 1.52, 2.48, 2.14, 0.90, 10.24. IV: 3.52, 1.62, 3.20, 2.74, 1.68, 12.76. Palp: 1.78, 0.62, 1.12,–, 1.04, 4.56. Midwidths: femora I=86, II, III=0.90, IV=0.82; tibia I=0.74, II, III=0.72, IV=0.62. Abdomen 3.82 long, 2.40 wide.

Carapace. Fovea broad, recurved. Bristles: distributed radially from fovea; long single row of brown bristles on lateral margin; three thick anteromedially; on cephalic area, 18 long and short; anteromedian, five long; clypeus, 22 long and short.

Eyes ( Fig. 15 ). On low tubercle in 3 rows; width of group at its mid-length/head width at same point, 0.4; width of group in front, 1.0; width of group in back, 1.2; length of group, 0.8; diameter of eyes: AME 0.4, PME 0.1, ALE 0.3, PLE 0.2; minimum eye interspace: AME–AME 0.2, AME–ALE 0.1, ALE–ALE 0.6, ALE–PLE 0.2, PME–PLE adjacent, PME–PME 0.8; MOQ: front width, 0.9, back width, 1.0, length 0.6.

Chelicerae ( Figs 21 , 29 ). Short, yellowish, long bristles and hair on dorsal surface; rastellum consisting only of one small coniform spicule medially on distal edge; five large, 1 small promarginal tooth; two basomesal teeth.

Labium ( Figs 16 , 30 ). 0.80 wide, 0.40 long, with 8 pointed cuspules on anterior margin.

Maxillae ( Figs 16 , 30 ). 1.10 long, 0.60 wide, with two pointed cuspules on inner edge; thick bristles over entire ventral face; few long hairs on prolateral face, retrolateral face glabrous.

Sternum. 2.10 long, 1.60 wide; with two pairs of sigilla (anterior not evident), both pairs oval, marginal.

Legs ( Fig. 20 ). Formula 4123. Scopulae: on distal 2/3 of metatarsi I, II, few scopuliform hair distally on metatarsi III, absent on metatarsi IV; on tarsi III distinct and divided by setal band, tarsi IV, rudimentary and divided by scattered setae; low pro-ventrolateral coupling spur on tibia I carrying slender, blunt, slightly curved megaspine pointing away from tibia at almost acute angle (45°); distal area close to tibial spur with black pigmentation forming annulation and four strong spines (distal one slightly short and proximal ones long and with tapering ends) aligned in retroventral longitudinal row on tibiae I. On tibiae II, three retroventral longitudinal and one proventral distal spine but not on spur and less prominent than on spines on tibia I. ( Figs 20 , 31 ). Spines: leg I, fe d5, p1; ti v4 + 1 megaspine; leg II, fe p1, d4; ti v4; leg III, fe p1, d5; leg IV, fe p1, d5; palp: fe, p1, d3; ti, v8. Spines on metatarsi absent. Claws: paired claws bare; claw tufts present, strong. Trichobothria on tarsi: I, four clavate, seven filiform in distal half; II, three clavate, 12 filiform in distal half; III, five clavate distal half, 10 filiform in distal half; IV, three clavate mid-dorsally, 10 filiform in distal half; palpal tarsi with five clavate in centre and five to seven filiform in distal half.

Spinnerets. Posterior median spinnerets digitiform, 0.22 long, 0.10 wide at midpoint, 0.10 apart; posterior lateral spinnerets 1.60 long (0.80 basal, 0.60 middle, 0.20 apical), dome-shaped apically.

Palp ( Figs 17 , 32–34 ). Cymbium with scopula dorsodistally and thin scopula on ventrodistal; clavate trichobothria in centre, dorsally filiform in distal half. Palp roughly spheroidal, with dorsal depression in centre; embolus slender and straight, evenly narrowing towards tip.

Distribution. Known only from the type locality, Rameshwaram Island, Tamil Nadu, India ( Fig. 1 ).

Habitat. Spiders were found on tamarind trees in a plantation. The coastal vegetation has been replaced by plantations of tamarind, coconut, palm and Casuarina over the decades.

Burrow ( Figs 13, 14, 22 ). The nest is a short tube with doors at both ends making a rough ‘8’. These silken nests are built in shallow depressions on tree trunks and camouflaged with bark particles giving them a rough texture on the outer surface and trunk colouration. The spider nests were observed up to a height of three metres on tree trunks. They probably occur higher up on tree trunks and branches but we did not survey higher up due to physical limitations. Usually, empty nests with open doors are found close to active nests on tree trunks.

Figures

FIGURES 1 – 11. 1, Rameshwaram Island (from Google Earth). 2 – 11. Sason rameshwaram, sp. nov., female, scale = 1.00 mm. 2. Habitus, dorsal view. 3. Cephalothorax, dorsal view. 4. Sternum, 5. maxilla, labium, cuspules, ventral view. 6. Chelicera, front view showing rastellum present as single spicule (scale = 0.50 mm). 7. Chelicera, ventral view showing prolateral teeth. 8. Spinnerets, ventral view. 9. annulation on tibia, metatarsus, tarsus I, dorsal view. 10. leg IV claws (scale = 0.10 mm), retroventral view. 11. Palpal claw, lateral view (scale = 0.10 mm).

FIGURES 12 – 22. 12 – 14, 22. Sason rameshwaram sp. nov., female. 12. Spider in its nest, upper part of nest removed. 13. Empty nest with trapdoor open. 14. Spider in its nest, trapdoor open. 15 – 21, male, scale = 1.00 mm. 15. Eyes, dorsal view. 16. Cuspules on labium, ventral view. 17. Palpal tibiae, tarsi and bulbs, ventral view. 18, 19. Habitus, dorsal view. 20. Tibia I, ventral view. 21. Chelicerae, front view showing rastellar spine (arrow). 22. Female’s camouflaged nest on tamarind tree.

FIGURES 23 – 34. Sason rameshwaram sp. nov. (Scale 1.00 mm). 23 – 28. female. 23. cephalothorax and abdomen, dorsal view. 24. Eyes, dorsal view. 25. Chelicera, prolateral view. 26. Spinnerets, ventral view. 27. Sternum, maxillae and labium, ventral view. 28. Spermathecae of holotype, ventral view. 29 – 34. Male. 29. Chelicera with rastellar spicule. 30. Maxillae and labium. 31. Right tibia I, ventral view. 32 – 34. Male palp. 32. Retrolateral view. 33. Ventral view. 34. Prolateral view.