Potamonautes mutandensis ( 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 : 1841-1842

Potamonautes mutandensis ( Chace, 1942)

( Figures 3–5 , Table 2)

Potamon mutandensis Chace 1942: 194–197 , fig. 4, 5a–g.

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

Material examined

Type material. Uganda. Holotype: adult male (CW 25.7, CL 19.1, CH 9.5, FW 7.8), Mushongero, Lake Mutanda , Kigezi District, coll. A. Loveridge, 1 February 1939 ( MCZ 11232) . Paratype: Mushongero, Lake Mutanda , Kigezi District , coll. A. Loveridge, 1 February 1939 ( MCZ 11233); four adult males (CWs 22.5, 20.8, 20.5, 19.6), two adult females (CWs 25.1, 21.3) Lake Bunyonyi, Kigezi District, from

outflowing stream 100 m from the lake in the outflow stream, coll. R. H. Lowe, 21 November 1952 ( NHM 2010.214 – 219 ) .

Other material. Democratic Republic of Congo. Adult male (CW 21.6, CL 15.0, CH 7.4, FW 5.7) plus a number of incomplete specimens with detached legs, Lake Kivu , 12 December 1917, coll. Robin Kemp ( NHM 1917.12.12 6–25) .

Diagnosis

Carapace narrow (CW / CL 1.3), medium height ( CH / FW 1.22); surface smooth; postfrontal crest faint to absent; epibranchial tooth absent; exorbital tooth low; cervical grooves faint, very long; third maxilliped with faint vertical groove ( Figure 3A,B ); first carpal tooth low, blunt, followed by two or three granules; distal meral tooth distinct, pointed ( Figure 3A,C ); sternal sulcus s2 / s3 deep, running horizontally across sternum; sulcus s3 / s4 incomplete, deep on sides but missing in middle ( Figure 3C ); terminal article of GO1 turned strongly outward; distal margin of subterminal segment highest on medial side, forming pronounced shoulder, lowest on lateral side; margins of subterminal segment of GO1 with long setae ( Figure 4A–C ).

Distribution

Lake Mutanda and Lake Bunyonyi in Uganda, and Lake Kivu in the Democratic Republic of Congo. The type locality label reads Mushongero (1 ◦ 10 ′ 43 S, 29 ◦ 40 ′ 58 E, 1888 m asl), which is on the road close to the northeast shoreline of Lake Mutanda ( Figure 5 ) .

Conservation status

Potamonautes mutandensis was assessed as Endangered (EN) using the IUCN Red List criteria ( IUCN 2003; Cumberlidge et al. 2009, appendix) because of its limited range and vulnerability to invasive crayfish. However, the present study shows that this species is more widespread than previously thought, and that this species occurs over a wide range ( Figure 5 ). The conservation status of P. mutandensis (Cumberlidge 2008b) therefore needs to be reassessed in the light of the new records presented here.

Remarks

This revised diagnosis is intended to update the original description of this species by Chace (1942). Bott (1955) considered P. mutandensis to be a junior synonym of P. emini (Hilgendorf, 1892) from Tanzania. Reed and Cumberlidge (2006) provided a redescription of P. emini , plus photographs, illustrations and a distribution map of the species. Potamonautes mutandensis can be distinguished from P. emini by the following characters: the dactylus of the major cheliped of P. mutandensis is highly arched, whereas that of P. emini is only slightly arched; the superior margin of the carpus of the cheliped of P. mutandensis has only faint carinae, whereas these carinae are strong in P. emini ; episternal sulci s4 / e4, s5 / e5, s6 / e6, s7 / e7 are incomplete but still visible in P. mutandensis but absent and smooth in P. emini ; the distal margin of the subterminal segment of GO1 at the dorsal membrane is diagonal in P. mutandensis but U-shaped in P. emini ; and the medial and lateral margins of the dorsal membrane of GO1 are of subequal width in P. mutandensis , whereas the lateral margin is longer than the medial margin in P. emini ; finally, the medial and lateral folds of the terminal article of GO1 are even in P. mutandensis , whereas the lateral fold is higher than the medial fold in P. emini .

Figures

Figure 3. Potamonautes mutandensis (Chace, 1942). (A) Dorsal view; (B) frontal view; (C) sternal view. Adult male (NHM 1917.12.12 6–25), CW 21.6.

Figure 4. Potamonautes mutandensis (Chace, 1942). (A) GO1, ventral view; (B) GO1, dorsal view; (C) GO2, ventral view. Adult male (NHM 1917.12.12 6–25), length of the terminal article measured along the mid-line of the dorsal face from tip to dorsal membrane 1.7 mm.

Figure 5. Distribution of Potamonautes mutandensis. Star, type locality; black circles, other localities. Scale bar 70 km.