Potamonautes idjwiensis ( Chace, 1942 )

Cumberlidge, Neil & Meyer, Kirstin S., 2011, The freshwater crabs of Lake Kivu (Crustacea: Decapoda: Brachyura: Potamonautidae), Journal of Natural History 45 (29 - 30), pp. 1835-1857 : 1837-1838

Potamonautes idjwiensis ( Chace, 1942)

( Figures 1 , 2 , Table 2)

Potamon idjwiensis Chace 1942, p. 197 –200, figs. 6,7.

Potamonautes idjwiensis: Ng et al. 2008: 171 ; Cumberlidge et al. 2009: Appendix 1.

Material examined

Type material. Democratic Republic of Congo. Holotype. Adult male (CW 37.1, CL 24.9, CH 14.5, FW 10.2) Idjwi Island , Lake Kivu coll. A. Loveridge, February 1939 ( MCZ 11234); paratypes, 89 males, 106 females (11 ovigerous, 1 with hatchlings) Idjwi Island, Lake Kivu coll. A. Loveridge, February 1939 ( MCZ 11235).

Other material. Two juvenile males (CW 22.9, CL 16.3, CH 9.3, FW 6.9; CW 21.0, CL 15.1, CH 8.1, FW 6.6) Lake Kivu, coll. Gillet, Bredin Expedition, 20 May 1955, ( USNM 98923 ) ; adult male (CW 36.2, CL 24.8, CH 14.0, FW 9.1) near Bukavu , Lake Kivu , coll. W. L. Schmitt, Bredin Expedition, 1955 ( USNM 98924 A); adult female (CW 33.8, CL 22.4, CH 12.9, FW 9.3) near Bukavu, Lake Kivu, coll. W. L. Schmitt, Bredin Expedition, 1955 ( USNM 98924 B) .

Diagnosis

Carapace highly arched ( CH / FW 1.42), surface smooth; postfrontal crest faint, almost absent; third maxilliped with faint vertical groove ( Figure 1A,B ); ventral margins of merus of pereiopod 1 weakly granulated; distal meral tooth low, blunt; first carpal tooth low, blunt, followed by small granules ( Figure 1A,C ); sternal sulcus s2 / s3 deep, completely crossing sternum; s3 / s4 deep, meeting top of sternoabdominal cavity; telson of male abdomen with concave sides ( Figure 1C ); subterminal article of GO1 with strongly setose margins; distal margin of subterminal segment highest on medial side, forming pronounced shoulder, lowest on lateral side; terminal article of GO1 straight, slimmer than subterminal article, curving only slightly outward; GO2 terminal article straight, flagellum-like ( Figure 2A–C ).

Distribution

Bukavu and Idjwi Island, Lake Kivu, Democratic Republic of Congo.

Conservation status

Potamonautes idjwiensis was assessed as Endangered (EN) using the IUCN Red List criteria ( IUCN 2003; Cumberlidge et al. 2009, Appendix 1) (where it is incorrectly spelled as P. idjiwiensis ) because it is restricted to two localities from Lake Kivu and therefore has a restricted area of occupancy. No new specimens have been collected since 1942, suggesting that the population may be in decline ( Cumberlidge 2008a).

Remarks

This revised diagnosis is intended to update the original description of this species by Chace (1942). Bott (1955) considered P. idjwiensis to be a junior synonym of P. (G.) granviki (Colosi 1924) but that opinion was not accepted by later authors ( Ng et al. 2008; Cumberlidge and Clark 2010) who considered P. idjwiensis to be a valid species. Potamonautes idjwiensis can be distinguished from P. loveni as follows. The postfrontal crest is absent in P. idjwiensis but faint and incomplete in P. loveni ; sternal sulcus s3 / s4 is deep and complete and meets the top of the sternoabdominal cavity in P. idjwiensis , but is deep at the sides and missing in the middle in P. loveni ; the dactylus of the major cheliped in P. idjwiensis is only slightly arched and bears several small teeth, whereas in P. loveni the dactylus is highly arched and lacks dentition; finally, the terminal article of GO1 curves slightly upward in P. idjwiensis but is straight-sided and tapers evenly to a tip in P. loveni .

Figures

Figure 1. Potamonautes idjwiensis (Chace, 1942). (A) Dorsal view; (B) frontal view; (C) sternal view; (D) right cheliped, frontal view. Adult male (USNM 98923), CW 36.2.

Figure 2. Potamonautes idjwiensis (Chace, 1942). (A) GO1, ventral view; (B) GO1, dorsal view; (C) GO2, ventral view. Adult male (USNM 98923), length of the terminal article measured along the mid-line of the dorsal face from tip to dorsal membrane 2.5 mm.