Potamonautes odhneri ( Colosi, 1924 )

Cumberlidge, Neil, 2009, A revision of the freshwater crabs of Mt Kenya and the Aberdare Mountains, Kenya, East Africa (Brachyura: Potamoidea: Potamonautidae)., Zootaxa 1981, pp. 29-42 : 33-36

Potamonautes odhneri ( Colosi, 1924)

( Figs. 17–29 , 44 , Table 1 )

Potamon (Potamonautes) odhneri Colosi, 1924: 7 –8, figs. 1, 3, pl. 4. Potamon odhneri Chace, 1942: 218 .

Type material examined. KENYA: Mt Kenya, 2,500 m asl, adult male (CW 23.5, CL 21 mm), figured by Colosi (1924), lectotype (here designated), 1911 (E. Lönnberg) ( SMNH 7558 [ex. 11859, ex. 6430]); adult female (CW 23.5 mm), abdomen very broad but no eggs or hatchlings, paratype (here designated) (CW 25, CL 17.9, CH 9.3, FW 7.9 mm), forest near Meru, north of Mt Kenya, 19–30.i.1911 (E. Lönnberg) ( SMNH 7557 [ex. 11852]) ( Figs. 17–25 ); Limuru, southern Aberdare Mountains, 2 adult females, paratypes (here designated) (largest CW 25.5, CL 16.9, CH 11.4, FW 7.8 mm).

Other material. KENYA: northern Aberdare Mountains, Chania River below Kiandongoro Forestry station (2,187 m asl) (0°27'S, 36°50'E), river shallow, 6–9 m wide, river bed stony with boulders, partly tree shaded, adult male (CW 25.5, CL 16.9, CH 11.4, FW 7.8 mm) 17.iii.1962 (T. R. Williams coll.) (NMU EA62.114); Gituambugi/Mutonga Rivers, eastern slope of Mt Kenya, 2 males (CWs 23.6, 22.2 mm), iv.2003 (A. Magana coll.) (NMU 4.2003.1); Nano Moru River west of Mount Kenya, adult male (CW 32.5 mm) 14.7.2004 (M. Dobson coll.) (NMU MD 14.7.2004); Mt Kenya, Smithsonian Africa Expedition (Theodore Roosevelt coll.) x.1909 ( USNM 57304); Mt Kenya, adult male, CW 24.1 mm ( USNM 82312) ( Figs. 26–29 , 44 ).

Diagnosis. Carapace smooth; anterolateral margin behind epibranchial tooth faintly granulated, curving inward over carapace in branchial region; postfrontal crest sharp; exorbital tooth low, epibranchial tooth reduced to a granule; carapace sidewalls smooth; vertical groove meeting anterolateral margin; sternal sulcus s2/s3 complete, horizontal, s3/s4 reduced to two side notches; episternal sulci s4/e4, s5/e5, s6/e6, s7/e7 all visible; third maxilliped ischium with vertical groove; first carpal tooth of cheliped carpus chsmall, pointed, second carpal tooth small, granular, followed by several other granules; dactylus of major cheliped highly arched, closed fingers enclosing wide oval interspace; terminal article of G1 curving sharply outward at 45° angle to longitudinal axis of gonopod; lateral, medial folds unequal, high; distal margin of subterminal segment highest on medial side forming pronounced shoulder lowest on lateral side; dorsal membrane broad, widest at lateral edge, narrowest at medial edge.

Size. Small-sized species, pubertal molt occurring around CW 23.5 mm, adult size range up to CW 32.5 mm.

Type locality. Mt Kenya and the Aberdare Mountains, Kenya.

Distribution. Mt Kenya and the Aberdare Mountains, in the highlands of central Kenya.

Remarks. This species was originally described from an adult female, so this is the first time that the gonopods, sternum, and chelipeds of P. odhneri have been described. The specimens from Mt Kenya and the Aberdare Mountains included here were identified following comparison with the male lectotype and the female paratype of Potamon (Potamonautes) odhneri from the forest near Meru, north of Mt Kenya (SMNH 7557), which was examined in the present study and figured by Colosi (1924). Bott (1955) treated P. odhneri as a junior synonym of Potamonautes (Platypotamonautes) pilosus ( Hilgendorf, 1898) . However, Reed & Cumberlidge (2006) doubted this synonymization following examination of the female paratype of P. (P.) odhneri from Meru, Kenya and the male lectotype of Telphusa pilosa Hilgendorf, 1898 (ZMB 11387) from a rain forest near Maranga at the base of Mt Kilimanjaro, Tanzania. Those authors pointed out that Bott’s (1955) photographs of P. p i l o s u s (Pl. V, 1a–d) actually show the female paratype of P. (P.) odhneri Colosi, 1924 (SMNH 7558, CW 23, CL 17, CH 10, FW 7.5 mm) from Limuru, near Mt Kenya, Kenya, and not the lectotype of T. pilosus . In addition, Williams (1968) also doubted Bott’s (1955) opinion regarding these two taxa. Potamonautes odhneri is therefore resurrected from synonomy and recognized here as a valid species.

Conservation status. The conservation status of P. odhneri is categorized as least concern (LC) because it has an extent of occurrence and an area of occupancy that are both in excess of the thresholds for vulnerable (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 the fact that it is well represented in museum collections, and because it has been collected recently.

Figures

FIGURES 17 – 25. Potamonautes odhneri (Colosi, 1924) adult femaleparatype (CW 25 mm) (SMNH 7557), Mt Kenya, Kenya. 17, carapace and eyes, dorsal view; 18, cephalothorax, carapace and eyes, frontal view; 19, carpus and merus of right cheliped, dorsal view; 20, merus of right cheliped, inferior view; 21; right cheliped, frontal view; 22, left cheliped, frontal view; 23, left third maxilliped; 24, left mandible; 25, detail of terminal segment of the palp of the left mandible. Scale = 6.1 mm (17 – 20, 21 – 23); 3.3 mm (24 – 25).

FIGURES 26 – 29. Potamonautes odhneri (Colosi, 1924) adult male (CW 24.1 mm) (USNM 82312), Mt Kenya, Kenya. 26, anterior sternum; 27, right G 1, ventral aspect; 28, right G 1, dorsal aspect; 29, gonopod 2, ventral aspect. Scale = 3.3 mm.

FIGURES 43 – 45. Right G 1, dorsal aspect. 43, Potamonautes jeanneli (Bouvier, 1921) adult male (CW 21.2 mm) (NMU TRW EA 62.78), Sirimon River, Mt Kenya, Kenya; 44, Potamonautes odhneri (Colosi, 1924) adult male (CW 24.1 mm) (USNM 82312) from Mt Kenya, Kenya; 45, Potamonautes alluaudi (Bouvier, 1921) adult male, CW 54 mm (NMU TRW 1963.02 a. 1 – 2), Chania River, Nyeri, Aberdare Mountains, Kenya. Sizes adjusted for comparative purposes.