Taxonomic revision of the endemic Cameroonian freshwater crab genus Louisea Cumberlidge, 1994 (Crustacea, Decapoda, Brachyura, Potamonautidae), with descriptions of two new species from Nkongsamba and Yabassi Author Mvogo Ndongo, Pierre A. Author von Rintelen, Thomas Author Cumberlidge, Neil text ZooKeys 2019 881 135 164 http://dx.doi.org/10.3897/zookeys.881.36744 journal article http://dx.doi.org/10.3897/zookeys.881.36744 1313-2970-881-135 B058CA156A3D41A19ADFD00384234D8E 16F69FEA95835AE5BF6B9C34F83E49D7 Louisea yabassi sp. nov. Figs 2c , 3c , 4d , 5c , 6c , 7c , 8e, f , 9c , 10c , 11c , 12c , 13c , 14c , 15c Material examined. CAMEROON. Holotype: adult male (CW 18.11 mm, CL 12.78 mm, CH 8.30 mm, FW 6.29 mm; CW/FW 2.88, CL/FW 2.03, CH/FW 1.32, FW/CL 0.49, FW/CW 0.34), Yabassi, 10 September 1909, coll. Riggenbach (ZMB Crust. 21575). Paratype: subadult male (CW 13.82 mm, CL 10.61 mm, CH 6.25 mm, FW 5.01 mm; CW/FW 2.75, CL/FW 2.11, CH/FW 1.24, FW/CL 0.47, FW/CW 0.36), same data as holotype (ZMB Crust. 21575). Diagnosis. Carapace smooth, urogastric groove faint; postfrontal crest distinct, prominent, complete, meeting anterolateral margin behind intermediate tooth ( Fig. 3c ); exorbital, intermediate teeth large, triangular; epibranchial tooth undetectable ( Figs 4c , 7c ). Vertical sulcus on carapace branchiostegal wall curving backward to meet anterolateral margin at epibranchial tooth ( Fig. 6c ). Mandibular palp bi-segmented; terminal segment (TS) bilobed, with large distinct anterior lobe 0.6 x terminal segment length ( Fig. 15c ). Third maxilliped ischium with distinct vertical groove ( Fig. 14c ). Episternal sulci s4/e4, s5/e5, s6/e6 faint or missing, s7/e7 complete ( Fig. 5c ). Major cheliped dactylus highly arched enclosing oval interspace when closed, with five large teeth (one small distal, two large medial, two small proximal) ( Fig. 8e ); propodus of major cheliped with two large proximal teeth, large medial tooth, small distal tooth ( Fig. 8e ); cheliped carpus inner margin with long, broad distal tooth, relatively narrow, subequal proximal tooth ( Fig. 10c ). G1TA short (TA/SS 0.22), directed outwards at 45° angle to longitudinal axis of G1SS, with distinct longitudinal groove proximally distinctly broad, abruptly narrow, slim and tube-like at distal two-thirds ( Figs 11c , 12c ). G1SS tapering slightly from broad basal margin to relatively wide distal margin (0.5 x SS basal margin); dorsal face with broad dorsal membrane (maximum width 0.1 x SS length) at TA/SS junction ( Fig. 11c ). G2TA long (TA/SS 0.44), flagellum-like, almost as long as G2SS ( Fig. 13c ). Mature at CW 19 mm. Description. Carapace ovoid, flat (CH/FW 1.28, N = 2), wide (CW/FW 2.8), smooth, urogastric groove distinct; front wide (FW/CW 0.35, N = 2), deflexed, anterior margin straight; postfrontal crest distinct, prominent, completely crossing carapace, meeting anterolateral margin of carapace behind intermediate tooth ( Fig. 4d ); exorbital, intermediate teeth large, triangular; epibranchial tooth undetectable ( Figs 4c , 7c ). Carapace branchiostegal sidewall with vertical, longitudinal sutures dividing it into three regions (suborbital, subhepatic, pterygostomial) ( Fig. 6c ); longitudinal suture beginning at respiratory opening, curving backward across sidewall dividing suborbital- and subhepatic regions from pterygostomial region ( Fig. 6c ); vertical sulcus on carapace branchiostegal wall curving backward to meet anterolateral margin at epibranchial tooth ( Fig. 6c ), dividing suborbital from subhepatic regions ( Fig. 6c ). Mandibular palp bi-segmented; terminal segment (TS) bilobed, with large distinct anterior lobe 0.6 x terminal segment length ( Fig. 15c ). Third maxilliped exopod completely lacking flagellum; ischium with distinct vertical groove ( Fig. 14c ). Sternal sulcus s2/s3 prominent, completely crossing sternum; s3/s4 incomplete, reduced to 2 short lateral notches ( Fig. 5c ). Episternal sulci s4/e4, s5/e5, s6/e6 faint or missing, s7/e7 complete ( Fig. 5c ). Male chelipeds unequal, right chelipeds larger than left cheliped; fingers slim, elongated. Right (major) cheliped dactylus relatively stout, straight, with five large teeth (one small distal, two large medial, two small proximal); fixed finger (pollex) with five large teeth (one distal, four proximal) ( Fig. 8e ); dactylus and propodus of left cheliped straight, with small teeth on occluding margin ( Fig. 8f ); cheliped carpus inner margin with two pointed teeth, distal tooth large with pointed tip, proximal tooth smaller ( Fig. 10c ); medial inferior margin of cheliped merus with large jagged distal tooth followed by numerous distinct smaller teeth ( Fig. 9c ). Male pleon triangular, sides not indented with small setae; telson (a7) rounded at distal margin ( Fig. 5c ). G1TA short (TA/SS 0.22), directed outwards at 45° angle to longitudinal axis of G1SS, with distinct longitudinal groove on ventral face, proximally distinctly broad, abruptly narrow, slim and tube-like at distal two-thirds ( Figs 11c , 12c ). G1SS tapering slightly from broad basal margin to relatively wide distal margin (0.5 x SS basal margin); ventral face of with raised triangular flap extending halfway across segment forming roof of chamber for G2, flap tapering diagonally from broad base to narrow point at SS/TA junction ( Fig. 12c ); dorsal face with broad dorsal membrane (maximum width 0.1 x SS length) at TA/SS junction ( Fig. 11c ). G2TA long (TA/SS 0.44), flagellum-like, almost as long as G2SS ( Fig. 13c ). Mature at CW 19 mm. Color in life. Unknown. Type locality. Yabassi, littoral region of Cameroon. Etymology. The new species is named for Yabassi in south-western Cameroon, where it was collected in 1909. The species epithet is a noun in apposition. Habitat. Louisea yabassi sp. nov. is known only from Yabassi, a humid area of the coastal rain forest of southwestern Cameroon. It is possible that this species is also present in the Ebo forest near Yabassi, which is one of the largest remaining tracts of lowland and submontane rainforest in the area. Remarks. Characters of the carapace and chelipeds of adult male specimens from Yabassi assigned to L. edeaensis by Cumberlidge (1994) and by Mvogo Ndongo et al. (2017a) proved to be inconsistent with the holotype from Edea. Re-examination of these specimens supported the hypothesis that specimens from Edea and those from Yabassi belong to two different species: L. edeaensis (Edea, Yaounde, and Lake Ossa) and L. yabassi sp. nov. (Yabassi). The differences between L. yabassi sp. nov. and its congeners are discussed below under general remarks. Figure 15. Four species of Louisea endemic to southwestern Cameroon, ventral view of right mandible. a Second largest adult male (CW 16.1 mm) of L. edeaensis from Lake Ossa wetland complex (ZMB Crust. 30335) b largest adult male (CW 16.2 mm) of L. balssi from Man's Crater Lake Manengouba (ZMB Crust. 30319) c adult male, holotype (CW 18.1 mm) of L. yabassi sp. nov. from Yabassi (ZMB Crust. 21575) d largest adult male, holotype (CW 20.0 mm) of L. nkongsamba sp. nov. from Mt. Nlonako (ZMB Crust. 31618). Scale bars: 1 mm ( a, c ), 2 mm ( b, d ).