Potamonautes platynotus ( Cunnington, 1907 )

Reed, Sadie K. & Cumberlidge, Neil, 2006, Brachyura: Potamoidea: Potamonautidae, Platythelphusidae, Deckeniidae (), Zootaxa 1262 (1), pp. 1-139 : 1-139

10. Potamonautes platynotus ( Cunnington, 1907) (Figs. 93–103, 163–164, 182, plate X)

Potamon (Potamonautes) platynotus Cunnington, 1907: 264–266 , pl. 17, fig. 1–2.

Potamonautes platynotus — Balss, 1929: 349–350; 1936: 185; Cumberlidge, 1998: 203–204; Cumberlidge et al., 1999: 1488; Cumberlidge & Sternberg, 1999: 406, table 1, fig. 1;: Sternberg & Cumberlidge, 1999: 134.

Potamon platynotus — Chace, 1942: 220.

Potamonautes (Platypotamonautes) platynotus — Bott, 1955: 235–236, pl. IV, fig. 1a–d, 12, 66; Coulter, 1991: 253–255, fig. 4, tables 9.xx, 9.xxi.

Type material examined: TANZANIA: Lake Tanganyika , male (cw 30.7, 20.3 mm), female (cw 48.2, cl 33.7 mm) .

Additional material examined: TANZANIA: Lake Tanganyika , Kigoma, from under stones at margin of lake, male (cw 39.1 mm), 23.iv.1971 (J. N. Raybould) ( NMU TRW1997.18 ) . DEMOCRATIC REPUBLIC OF THE CONGO: Lake Tanganyika , female (cw 31.6 mm), male (cw 23.8 mm), ( USNM 63298 ) ; Lake Tanganyika , 2 males (cws 20.2, 36.3 mm), 3 females (cw 20.2 to cw 22.6 mm), juvenile (cw 11.9 mm), 19.v.1955 (Bredin Expedition­W. L. Schmitt) ( USNM 98935 ) ; Lake Tanganyika, Mulungu , female (dried), vi–viii.1955 (Bredin Expedition­W. L. Schmitt) ( USNM 98934 ) . ZAMBIA: Lake Tanganyika, north end of Mpulungu , Northern Province, depth of capture 0–4 m, male (cw 45.6 mm), subadult female (cw 38.1 mm), 1.xi.1970 (Dr. R. M. Bailey, Stewart, Cech et al.) ( USNM 1007569 ) .

Diagnosis. Postfrontal crest distinct complete; grooves on posterior region of carapace deep; exorbital tooth large, forward­pointing spine, epibranchial tooth small, pointed; anterolateral margin between exorbital, epibranchial teeth lined by row of small even, pointed teeth; ischium of third maxilliped faint; thoracic sternal sulcus s3/s4 complete, deep at sides, faint in middle; dactylus of major cheliped of adult males broad, arched with large molar teeth proximally, black pigment distally; propodus of cheliped broad with several large rounded molar teeth, lower margin of propodus of cheliped straight; first carpal tooth on carpus of cheliped long, sharp spine; second carpal tooth also sharp spine, but smaller than first tooth; ventral margins of merus of pereiopod 1 heavily granulated, distal meral tooth sharp spine; terminal article of gonopod 1 short, cone­like, directed outward, with distinct bristles along both margins; basal part broad distal part narrow with upcurved tip; basal part significantly widened by high lateral fold becoming low, even distally; medial fold low, even along length; base of terminal article at dorsal membrane lined with long, dense bristles; distal margin of subterminal segment highest at lateral margin curving down to medial margin; dorsal membrane subrectangular, broad at both lateral, medial sides.

Size. Medium size, with a pubertal molt around cw 39 mm. The largest specimen known is cw 54.2 mm.

Variation. The dactylus of the major cheliped is dark brown/black in the middle and the anterior margin of the propodus of the major cheliped is rose colored.

Type locality. Lake Tanganyika .

Distribution. Lake Tanganyika, Tanzania, Democratic Republic of Congo and Zambia ( Capart 1954; Cumberlidge et al. 1999).

Remarks. This species is endemic to Lake Tanganyika in Tanzania, the Democratic Republic of Congo and Zambia ( Capart 1954; Cumberlidge et al. 1999).

Natural history and conservation status. Potamonautes platynotus occurs in rocky areas in Lake Tanganyika and is mainly found in the shallow littoral zone up to a maximum depth of approximately 10 meters. This species is primarily aquatic, but it has been observed out of water feeding on top of rocks, and it can survive for several hours (up to half a day) without access to water (S. Marijnissen, pers. comm.). The conservation status of P. platynotus is categorized as least concern (LC) ( Table 4) because it has a range of occurrence and an area of occupancy in excess of the thresholds for vulnerable (VU) ( IUCN 2004). Its population is estimated to be stable based on indirect measures such as the fact that a lot of material has been collected recently from more than one locality (S. Marijnissen, pers. comm.), that it is supplied to the international aquarium trade and that it is well represented in museum collections.