Platythelphusa tuberculata Capart, 1952

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

25. Platythelphusa tuberculata Capart, 1952 (Fig. 197, plate XXV)

Platythelphusa tuberculata Capart, 1952: 50–52 , figs. 4, 7c; Cumberlidge, 1999: 277; Cumberlidge et al., 1999: 1506–1507, fig. 4, 7f–g, 8d, m,n, 9d, 10l–o.; Marijnissen et al., 2004: 528–530, Tables 1, 2.

Potamonautes (Platythelphusa) tuberculata — Coulter, 1991: 253–255, tables 9.XX, 9.XXI.

Type material examined: DEMOCRATIC REPUBLIC OF CONGO: Lake Tanganyika , vicinity of Moba, 20 m deep (station 38), male subadult paratype (cw 16.4 mm), donated by A. Capart, 23.XI.1952 ( BMNH 1952.10.23.28) .

Additional material examined: BURUNDI: Ruzizi river mouth, 15–30 m deep; 2 adult males (cws 31.4, 37.3 mm), adult female (cw 30.6 mm), lake­bed soft mud, caught in gill nets, 1.vi.1993, (CAW 12A) .

Diagnosis. Carapace subhexagonal, rounded, wide (cw/fw 2.95), very long (cl/fw 2.49), very high (ch/fw 1.14). Frontal margin granular, indented in middle, with distinct forward pointing tooth at each external corner. Exorbital tooth pointed, directed forward; epibranchial tooth large, pointed. Two large subequal forward­pointing teeth on anterolateral margin behind epibranchial tooth. Suborbital margin lined by small granules, large pointed tooth at medial end. Epimeral sulcus on sidewalls of carapace, vertical sulcus between epimeral sulcus and base of epibranchial tooth. Lateral inferior margin of merus of cheliped lined by series of distinct pointed teeth, single large pointed tooth on medial inferior margin; superior margin with single spine or carinae. Inner margin of carpus of cheliped with two large subequal medial teeth, articular tooth (at point of articulation with propodus) broad, pointed, low; outer margin of carpus with row of small granules and posterior spine. Ischium of cheliped with sharp spine on inferior lateral margin. Merus of p5 much longer than fw, superior margin with sharp distal tooth. Propodi of p4, p5 extremely long, thin, margins of propodi of p4, p5 smooth. Dactyli of p2–p5 very long, slim, curved, rows of spines very reduced. Terminal article of gonopod 1 directed outward at a 60° angle to vertical, slim, cone­shaped, tapering to pointed tip.

Description. See Capart (1952), Cumberlidge et al. (1999) and Marijnissen et al. (2004).

Size. The adult size range is from cw 30.6 to cw 37.3 mm.

Distribution. Lake Tanganyika: Burundi, D. R. Congo. Collected in waters 100– 50 m deep where the lakebed is muddy. The type locality is at Moba in Burundi, 20 m deep. This distinct long­legged large species is found in deeper parts of the sublittoral zone in the northern end of the lake where the lakebed is muddy. This species has also been found in the stomachs of lake fish such as Chrysichthyes brachynema ( Capart 1952) and C. stappersi ( Coulter 1991).

Remarks. This species was redescribed by Cumberlidge et al. (1999), who provided details of its identification, distribution and ecology. Platythelphusa tuberculata was originally described by Capart (1952) from a subadult female specimen because no males were known. The diagnosis by Cumberlidge et al. (1999) was based on an adult male specimen and includes the first account of the gonopods, male abdomen, sternum and chelipeds of this species. Platythelphusa tuberculata can be distinguished from the other species in this genus by a large number of distinctive characters. These include the accentuated sculpture of the carapace regions, the strong spines on the lateral inferior margin of the merus of the cheliped, the large spine on the superior margin of the merus of the cheliped, the large spine on the external margin of the carpus of the cheliped, the highly arched and slim dactylus of the major cheliped of adult males, the elongated slim legs (the merus of p5 is much longer than the front width), the long, thin propodus of p5 and the very long, slim and curved dactyli of p2–p5 which have rows of very reduced spines.

Natural history and conservation status. The conservation status of P. tuberculata 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 material has been collected recently from more than one locality (S. Marijnissen, pers comm.)