Parathelphusa tenuipes ( Schenkel, 1902 )

Ng, Oliver K. S. Chia Peter K. L., 2006, The Freshwater Crabs Of Sulawesi, With Descriptions Of Two New Genera And Four New Species (Crustacea: Decapoda: Brachyura: Parathelphusidae), Raffles Bulletin of Zoology 54 (2), pp. 381-428 : 397-398

Parathelphusa tenuipes ( Schenkel, 1902)

( Fig. 15 )

Potamon (Potamonautes) celebensis var. tenuipes Schenkel, 1902: 530 .

Potamon celebense var. tenuipes - Roux, 1904: 565.

Potamon (Potamonautes) celebensis tenuipes - Rathbun, 1905: 199.

Parathelphusa (Meostelphusa) pallida (part) - Bott, 1970c: 128.

Material examined. – Holotype: female (32.6 x 24.4 mm) ( NMB 23 IIa), Lake Poso , Tomini Gulf, Central Sulawesi, coll. Gesch & Sarasin, 1901.

Diagnosis. – Carapace convex, inflated, dorsal surfaces smooth; cervical groove deep and distinct, almost reaching anterolateral margin; H-shaped central depression shallow. Epigastric and postorbital cristae continuous, sharp, subparallel to frontal margin; outer edge of cristae almost reaching anterolateral margin, stopping at base of first epibranchial tooth. Front almost straight, entire; frontal median triangle distinct, very broad, dorsal ridge distinct but weak and incomplete. Anterolateral margin smooth, external orbital angle broadly triangular, low, outer margin almost straight, about 2.2 times length of inner margin, first and second epibranchial teeth low but discernible, knob-like. Posterolateral regions lined with distinct oblique striae. Palm of chelipeds slightly inflated, fingers subequal to palm. Ambulatory legs relatively long, second pair longest. Dorsal margin of merus slightly cristate, without distinct subterminal spine.

Distribution. – Lake Poso, Central Sulawesi.

Remarks. – Schenkel (1902) only examined one female from Lake Poso, near Tomini Gulf when he described Potamon (Potamonautes) celebense var. tenuipes . It was regarded as a junior synonym of P. pallida by Bott (1970c). However, despite the species represented by only a single female type specimen, there are still sufficient characters that differentiate it from P. pallida , and it is here regarded as a valid species.

Parathelphusa tenuipes differs from P. pallida in the following characters. The cervical groove of P. tenuipes is deep and distinct, almost reaching the anterolateral margin ( Fig. 15A ), while the cervical groove of P. pallida is shallow but distinct, stopping well before the anterolateral margin ( Figs. 12A , 13A ). The frontal median triangle for P. tenuipes is very broad with the dorsal ridge being distinct but incomplete ( Fig. 15B ) while the frontal median triangle for P. pallida is relatively narrow but distinct with the dorsal ridge being distinct and complete ( Figs. 12B , 13B ). The width of the frontal median triangle does vary in some parathelphusid species and may be associated with the age and size of the specimen. Therefore to ascertain the value of this character, comparable sized specimens of P. pallida and P. celebensis were examined and compared with P. tenuipes . Examination of a large series of these species showed that at least for the Sulawesian species of Parathelphusa , there is little variability in this character and is thus a useful differentiating character for the species studied. The anterolateral margin of P. tenuipes is smooth while that of P. pallida is finely granulated. The first and second epibranchial teeth for P. tenuipes is low ( Fig. 15A ) but discernible and knob-like while that for P. pallida is barely discernible and almost confluent with the anterolateral margin ( Figs. 12A , 13A ). Lastly, the fingers of the chelipeds of P. tenuipes are comparatively longer, being subequal to the length of the palm ( Fig. 15 ) while the fingers of the cheliped for P. pallida are shorter then the length of the palm ( Figs. 12 , 13 ). However, the length of the fingers relative to the palm is known to be size- and sex-associated. In most freshwater crabs, females tend to have relatively more slender and longer fingers compared to males. Younger males have also been observed to have comparatively more slender fingers compared to larger males. However, comparisons have been made to a comparative sized female, and the difference in length of fingers between P. ternuipes and P. pallida , in this case cannot be attributed solely to allometric growth differences. As such, the length of the fingers in this case at least, is used as a differentiating character.

Figures

Fig. 15. Parathelphusa tenuipes (Schenkel, 1902), holotype female (32.6 x 24.4 mm, NMB 23IIa): A, dorsal view; B, frontal view; C, ventral view.

Fig. 12. Parathelphusa pallida (Schenkel, 1902), lectotype male (23.9 x 18.3 mm, NMB 23VIb): A, dorsal view; B, frontal view; C, ventral view.

Fig. 13. Parathelphusa pallida (Schenkel, 1902), female (NMB 23 Ia) (lectotype of Potamon (Potamonautes) celebensis var.annulipes Schenkel, 1902): A, dorsal view; B, frontal view; C, ventral view.