Potamonautes jeanneli Bouvier 1921

Potamonautes jeanneli (Bouvier, 1921)

(Figs. 1–16, 43, Table 1)

Potamon (Geothelphusa) jeanneli Bouvier, 1921: 51 –56, figs. 5, 6. Potamon jeanneli Chace, 1942: 214.

Potamon jeanneli Capart, 1954: 834, fig. 22.

Potamonautes jeanneli Williams, 1968: 214; Williams, 1991: 182.

Type material examined. KENYA: adult male, Potamon (Geothelphusa) jeanneli (CW 22, CL 19.5, CH 7.1, FW 7.4 mm), mid-altitude forest (2,400–2,700 m) on western slopes of Mt Kenya, 22.i.1912 (CH. Alluaud and R. Jeannel coll.). This specimen was illustrated by Bouvier (1921, figs. 5, 6) and is one of four adult males that he referred to as types, and is herein designated the lectotype (Figs. 1–16).

Other material. KENYA: Mt Kenya, Sirimon River (0°08'N, 37°06'E), 13–15 km north of Nanyuki on the road to Meru, 3.7 m wide, up to 0.6 m deep, part shaded, river bed with rounded stones, some larger blocks, 6 males (CWs 16.5 to CW 23.6 mm), one female (CW 14.5 mm) 8.iii.1962 (T. R. Williams) (NMU EA62.78).

Diagnosis. Carapace smooth; anterolateral margin behind epibranchial tooth smooth, continuous with posterolateral margin; postfrontal crest missing, epigastric crests low, postorbital crests absent; exorbital tooth low, epibranchial tooth absent; carapace sidewalls smooth; vertical groove meeting anterolateral margin; sternal sulcus s2/s3 complete, horizontal, s3/s4 reduced to two notches; episternal sulci s4/e4, s5/e5, s6/e6, s7/e7 all missing; ischium of third maxilliped lacking vertical groove; first carpal tooth on carpus of cheliped low, second carpal tooth smaller; dactylus of major cheliped slightly arched, closed fingers enclosing long narrow interspace; terminal article of G1 slim, almost straight, distal half curving slightly outward; lateral, medial folds of equal height; distal margin of subterminal segment highest on medial side forming pronounced shoul- der lowest on lateral side; dorsal membrane broad, widest at lateral edge, narrowest at medial edge.

Size. Small-sized species, adult size range from CW 22 to CW 23.6 mm.

Type locality. Kenya: mid-altitude forest on western slopes of Mt Kenya, from a fast-flowing mountain stream in a clearing in a bamboo forest (2,700 m asl).

Distribution. Kenya: Mt Kenya (2,400–2,700 m asl), from streams in mid-altitude bamboo forest, from the Burguret River on an ascent trail of Mt Kenya in a podocarp forest (2,400 m asl), and from the Sirimon River.

Natural history. This species lives in the rivers and streams draining the slopes of Mt Kenya and was first collected by members of the French Expedition led by Ch. Alluaud and R. Jeannel in 1912. Other material was collected fifty years later from Mt Kenya by T. R. Williams as part of an onchocerciasis study in 1962.

Comments. The male lectotype of Potamon (Geothelphusa) jeanneli from Mt Kenya (CW 22 mm) was partly figured by Bouvier (1921, figs 5, 6). Although this species was originally described from an adult male the gonopods, anterior sternum, and chelipeds are described here for the first time. Colosi (1924) identified a male specimen (CW 28.3 mm) from Mt Elgon collected by S. A. Lovén, 30.vi.1920, from a steam at 4,000 m asl (SMNH 7556 ex. 13215) as P. (G.) jeanneli. However, it is by no means certain that this specimen actually belongs to this species, because the sketches provided in the original description and the locality indicate that it might be a misidentified subadult specimen of P. l o v e n i (Colosi, 1924). Bott (1955) included Colosi’s (1924) P. (G.) jeanneli from Mt. Elgon in the synonymy of Potamonautes granviki, and treated Bouvier’s (1921) P. jeanneli from Mt Kenya, as a junior synonym of Potamonautes (Platypotamonautes) neumanni (Hilgendorf, 1898). However, the latter opinion is doubtful. The male lectotype of Telphusa neumanni (CW 35 mm) from Ngari Longai, Masailand, Kenya, 36°W, 1.5°S (ZMB 11386) was compared here with the adult male type of P. (G.) jeanneli from Mt Kenya (CW 22 mm). The G1 of P. jeanneli (Figs. 13–15) is clearly different from that of the lectotype of P. neumanni (Bott 1955, fig. 14) and this raises doubts about the validity of Bott’s (1955) synonymization. Potamonautes jeanneli is resurrected here from synonymy with P. (P.) n e u - manni and both taxa are treated as valid species.

Conservation status. The conservation status of P. jeanneli from Mt Kenya is assessed as least concern (LC) because it has an extent of occurrence and area of occupancy that are both in excess of the thresholds for vulnerability (VU) and there are no known widespread threats (IUCN 2004; Cumberlidge et al. 2009). Its population is estimated to be stable based on indirect measures such as its representation in museum collections, although it was most recently collected back in 1962