Potamonautes loveridgei ( Rathbun, 1933 )

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

6. Potamonautes loveridgei ( Rathbun, 1933) (Figs. 52–61, 155–156, 178, plate VI)

Potamon (Potamonautes) loveridgei Rathbun, 1933: 251–253 , pl. 1–2, fig. 3

Potamonautes johnstoni stappersi Balss, 1936: 182–184 , fig. 19.

Potamon loveridgei — Chace, 1942: 215.

Potamonautes (Tripotamonautes) loveridgei — Bott, 1955: 263, pl. XIV, fig. 1a–d, fig. 31. Potamonautes loveridgei — Cumberlidge, 1997: 583; 1998: 201.

Type material examined: TANZANIA: Potamon (Potmaonautes) loveridgei Rathbun, 1933 , male holotype Uzungwe (=Udzungwe) Mountains ( MCZ 7676). Potamon (Potamonautes) johnstoni stappersi Balss, 1936 : male type (cw 39.5, cl 26.8, ch 15.3, fw 11.0 mm), Sambala River.

Additional material examined: TANZANIA: Ujiji, Luicke River , 2 males (cw 34.8, 38.5 mm), 2 females (cws 39.8, 48.2 mm), 24.iii.1930 (A. Loveridge) ( USNM 64102 ) ; Rungwe Mountains, Nkuka Forest , 2 males (cws 23.6, 29.6 mm), 2 females (cws 18.3, 18.8 mm), 24.iii.1935 (A. Loveridge) ( USNM 64105 ) ; 32 km from Kigoma on road to Kasula , small stream, 2 males (cws 43.4, 54.2 mm), female (cw 52.4 mm), 17.iv.1971 ( T. R. Williams) ( NMU TRW1971.07 ) ; 2 juvenile males (cws 15.5, 34.6 mm), 2 females (cws 33.8, 33.9 mm), juvenile female (cw 13.5 mm); Lushoto District, 2 km north of Mayo , 2 juvenile males (cws 21.2, 28.5 mm), 11.iii.1975 ( T. R. Williams) ( NMU TRW1975.03 ) ; Lushoto District, 1 km west of Mayo , subadult female (cw 33.9 mm), juvenile (cw 15.7 mm), juvenile (damaged), male (damaged), 11.iii.1975 ( T. R. Williams) ( NMU TRW1975.07 ) ; 5 males (cw 30.5 to cw 40.5 mm), female (cw 38 mm), 4.xii.1966 (F. Malaisse) ( NMU TRW04.12.1966.1–6) .

Diagnosis. Postfrontal crest sharp complete; grooves on posterior part of carapace faint, shallow; exorbital tooth large, triangular, epibranchial tooth missing; anterolateral margin behind epibranchial tooth smooth, curving strongly outward; ischium of third maxilliped with deep vertical sulcus; thoracic sternal sulcus s3/s4 deep at sides, shallow across middle; margins of sternite s4 raised, rounded; dactylus of major cheliped of adult males broad but not arched; first carpal tooth on carpus of cheliped large sharp spine; second carpal tooth sharp spine smaller than first tooth; ventral margins of merus of pereiopod 1 both distinctly granulated; distal meral tooth sharp spine; first half of terminal article of gonopod 1 straight with parallel sides angled slightly outward, second half bent at 45° angle to longitudinal axis of gonopod tapering to pointed upcurved tip; terminal article of gonopod 1 significantly widened in middle by enlarged lateral fold forming high longitudinal crest; medial fold small, low; deep groove running along entire length of terminal article between two folds; base of terminal article curving down highest at medial margin; distal margin of subterminal segment at dorsal membrane straight; dorsal membrane subtriangular, with base of triangle on lateral margin, apex on medial margin.

Size. The adult size range is from cw 37.9 to cw 54.2 mm.

Variation. The chelipeds of P. loveridgei become heterochelic during the subadult and adult stages. This is most apparent in males where growth in the major cheliped results in the dactylus becoming highly arched, leaving a narrow gap between it and the fixed finger. The dactylus of the closed major cheliped in juveniles is straight and its teeth interlock with those of the fixed finger. The groove on the ischium of the third maxilliped varies from deep to weak and is deepest in younger crabs.

Type locality. Luiche River (Ujiji and Dabaga), Uzungwe (Uzongwe) (Rungwe) Mountains, Tanzania .

Distribution. Tanzania, Democratic Republic of Congo. Potamonautes loveridgei is found in the rivers that flow into Lake Tanganyika.

Remarks. These specimens were identified by comparison to illustrations of the male holotype of P. (P.) loveridgei Rathbun, 1933 from the Uzungwe Mountains (MCZ 7676). Our examination of the male type of P. (P.) johnstoni stappersi Balss, 1936 from the Sambala River in Tanzania leads us to regard this taxon as a junior subjective synonym of P. loveridgei . Balss (1936) illustrated the distinctive gonopod of P. loveridgei (as P. johnstoni stappersi ). The assignment by Bott (1955) of P. loveridgei to the subgenus (Tripotamonautes) is not recognized here due to doubts about the validity of that subgenus.

Natural history and conservation status. The conservation status of P. loveridgei 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 (present study; I. R. Bills, pers. comm.) and that it is well represented in museum collections