Nesiergus insulanus Simon, 1903

Canning, Gregory, Reilly, Brian Kevin & Dippenaar-Schoeman, Ansie S., 2013, First description of the male of Nesiergus insulanus (Araneae: Theraphosidae: Ischnocolinae) from the Seychelles archipelago, African Invertebrates 54 (1), pp. 241-241 : 242-244

Nesiergus insulanus Simon, 1903

Figs 1–6

Nesiergus insulanus: Simon 1903: 928 ; Benoit 1978: 412, fig.3; Smith 1990: 134, figs 878–882; Guadanucci & Gallon 2008: 43 , figs 26–28; Saaristo 2010: 31, fig. 3.10–15.

Diagnosis: Both sexes of the species are differentiated from other species in the genus by the apical segment of the PLS being triangular, as opposed to digitiform ( Guadanucci & Gallon 2008), as well as by the segments of these spinnerets being of dissimilar length. The species has dark markings on the abdomen, whilst its congeners are uniform in colour ( Guadanucci & Gallon 2008).

Description:

Male.

Size: Total length 17.63.

Colour: Live specimen ( Fig. 1 ) has reddish brown carapace with golden brown hairs around margin.Abdomen golden brown with markings significantly darker than rest of abdominal colouration. Markings consist of four that are triangular in shape, running along central dorsal line of abdomen, connected by dark line. Markings point anteriorly, decreasing in size towards posterior end of abdomen. They do not reach outer edge of abdomen; largest one being approximately ⅓ of abdomen width. Faint lines extend from corner of triangular areas towards outer edge of abdomen and are less pronounced than in females ( Fig. 2 ). Two bands, covered by hair, extend around abdomen at posterior end. Dorsal surface of femora of all legs darker brown than rest of legs and palps, which are golden brown.

Carapace: Length 8.03, width 6.63, sparsely pilose, oval, slightly longer than wide. Cephalic region raised. Eye tubercle slightly raised towards centre, wider than long, length 0.74, width 1.5.Anterior eye row procurved, posterior eye row recurved ( Fig. 3 ), with row of bristles between anterior tubercle and chelicerae. Distance between eyes: AME–ALE 0.30, ALE–PLE 0.35, PLE–PME 0.16, AME–PME 0.33, PME–PME 0.77,AME–AME 0.41, PLE–PLE 1.13. Clypeus narrow. Fovea transverse, slightly recurved.

Sternum rounded, oval, longer than wide, length 3.49, width 2.77, sparsely pilose, posterior end with row of longer setae. Small, oval pair of labiosternal mounds adjacent to labium. Three pairs of small, rounded sternal sigilla short distance from margin. Maxilla with anterior lobe; 102 or 103 cuspules on each maxilla on inner surface adjacent to labium, serrulae present on anterior lobe. Labium slightly longer than wide, length 1.26, width 1.12, with ca 47 cuspules limited to the centre. Chelicerae with 12 teeth of differing sizes on promargin ( Fig. 4 ).

Abdomen: Length 9.60, width 3.53, more densely pilose than carapace, longer setae at posterior end. Two pairs of spinnerets, PMS short; PLS longer, with segments of different lengths, basal segment shortest, apical segment triangular ( Fig. 5 ). Line of long, thick setae at anterior edge of abdomen.

Legs: Slender, sparsely pilose, thick band of setae on all legs at dorsal joint between coxa and femur. Measurements: I 5.50+2.61+5.59+4.20+2.79=20.69, II 5.20+2.14+ 5.43+4.18+3.76=20.71, III 5.37+1.90+4.49+4.78+3.48=20.02, IV 6.66+1.99+6.22+ 6.70+3.9=25.47. Spination: I femur (v) 0-1-1, tibia (v) 0-2-1 (p) 0-1-1 (r) 0-1-1, metatarsus (p) 0-1-0; II femur (v) 0-0-ap1 (r) 0-1-1, tibia (v) 1-0-ap2, metatarsus (v) 1-0-0; III femur (v) 0-1-0, tibia (v) 1-0-ap2 (p) 1-0-0 (r) 0-3-0, metatarsus (v) 0-0-ap2 (p) 0-0-ap; IV femur (p) 0-0-1(r) 0-0-1, tibia (v) 2-1-ap2, metatarsus (v) 1-1-2 (p) 1-1-2. Tarsal spines absent. Tibial apophysis on leg 1 fused at base, retrolateral branch with a row of short apical spines, prolateral branch short, rounded, with single spine adjacent to each branch ( Fig. 6 ). Ventral tarsal scopulae I–II undivided, dense, III divided, distal ¾ dense, proximal quarter sparse, IV divided, distal half dense, proximal half sparse. Claw tufts well developed.

Palp slender, sparsely pilose, spineless. Cymbium bilobed, longer than wide, bulb with long, fine embolus ( Fig. 7 ). Femur 3.63, patella 1.86, tibia 2.70, tarsus 0.84, total 9.03. Material examined: SEYCHELLES: Frégate Island: 1♂ 4°35'04.44"S 55°56'44.68"E, 8 m, wandering on sandy substrate, 11.i.2011, G. Canning (NCA 2013/757); 1♂ same data but 17.i.2011 (NCA 2012/2501) .

Figures

Figs1–6. Nesiergus insulanus: (1) male with abdominal markings and femora darker than other leg segments and palpi clearly visible; (2) female with abdominal markings clearly visible; (3) dorsal view of eye pattern,displaying procurved anterior row andrecurved posterior row; (4) ventral view of chelicerae, indicating position of fangs and size and arrangement of cheliceral teeth on promargin; (5) male spinnerets, showing PLS with differing segment lengths and diagnostic triangular apical segments; (6) tibial apophysis.

Fig. 7. Schematic retrolateral view of palpal bulb of Nesiergus insulanus.