Potamonautes gonocristatus Bott, 1955

(Fig. 6–8, Table 1, 2)

Potamonautes (Lobopotamonautes) perparvus gonocristatus Bott 1955: 285, fig. 51; plate 22, fig. 1 a–d. Potamonautes perparvus gonocristatus— Ng et al. 2008: 171.

Potamonautes gonocristatus— Cumberlidge et al. 2009: appendix item 914.

Type material examined. DR CONGO: Upper Congo adjacent to Lake Kivu, Tschiwia stream and Mukoba, Kahuzi-Biega National Park, 2250 m asl, adult male (CW 19.3, CL 13.5, CH 7.2, FW 6.0 mm) (MRAC 37410, ex. SMF); Upper Congo adjacent to Lake Kivu, Luika, adult male paratype (R. Laurent) (SMF 2431).

Other material examined. DR CONGO: Utu, Walikale region, near Lake Kivu, 1800 m asl, ovigerous adult female (CW 22.9, CL 17.5, CH 7.9, FW 5.7) 28 Sep. 1972 (Alan Goodall) (NMU 1972.09).

Diagnosis. Carapace medium height (CH /FW 1.2), surface smooth, postfrontal crest faint to absent; exorbital tooth reduced to small granule, epibranchial tooth absent, anterolateral margin lined by granules; horizontal sulcus on carapace sidewall lined by granules; ischium of third maxilliped with faint vertical sulcus; sternal sulcus s2/s3 faint depression; s3/s4 reduced to two side notches, not meeting top of sac; first carpal tooth on carpus of cheliped distinct, pointed; second carpal tooth small, pointed, followed by several granules; distal meral tooth of P1 merus distinct, pointed; fixed finger of propodus of major cheliped lined with low, rounded teeth, two of which are prominent; dactylus of major cheliped lined by small rounded teeth, one of which is prominent, dactylus relatively straight, fingers enclosing long narrow interspace; terminal article of G1 with slim base, significantly widened in middle, curving upward to slim tip, lateral fold much higher than medial fold; groove on terminal article visible on dorsal face; dorsal membrane trapezoidal, medial margin wider than lateral margin (Figs. 6, 7).

Size. A small species with an adult size range of CW 19-23 mm

Type locality. DR Congo: Upper Congo near to Lake Kivu, Tschiwia stream and Mukoba, Kahuzi-Biega National Park, 2250 m asl (Fig. 8).

Conservation status. Potamonautes gonocristatus was listed as “endangered” (IUCN 2003; Cumberlidge et al. 2009) because its extent of occurrence is very restricted and all individuals are found in just five localities. In addition, there are potential threats that may result in a decline in the extent and quality of its habitat and this species is not found in a protected area (Cumberlidge 2008c).

Distribution. DR Congo: Rivers of the Congo River and Lake Kivu drainage basins, Democratic Republic of the Congo (Fig. 8; Table 2). Although P. gonocristatus was considered previously endemic to Lake Kivu (Cumberlidge 2008c), the data presented here show this is not true. It is present at a few localities in the mountainous streams and rivers west of Lake Kivu in the Congo River basin (Fig. 8).

Remarks. Bott (1955) considered P. gonocristatus and P. minor to be subspecies of P. perparvus presumably because all three are small-size species with similar distributional ranges, and all have smooth carapaces, small exorbital teeth, and all lack an epibranchial tooth. Potamonautes gonocristatus can be differentiated from P. m i n o r and P. p e r p a r v u s by the following characters: the anterolateral margin is lined by granules in P. gonocristatus and smooth in P. minor and P. perparvus; the horizontal sulcus on the carapace sidewall is lined by granules in P. gonocristatus but smooth in P. minor and P. perparvus; sternal sulcus s2/s3 is a faint depression in P. gonocristatus but deep in P. m i n o r and P. perparvus; sternal sulcus s3/s4 is reduced to two side notches and does not meet the top of the sternoabdominal cavity in P. gonocristatus, whereas it is complete and meets the top of the sternoabdominal cavity in P. m i n o r and P. perparvus; and the dorsal membrane of G1 has a medial margin that is wider than the lateral margin in P. gonocristatus, whereas these margins are even in P. m i no r (Table 1).