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 Genus Louisea Cumberlidge, 1994 Globonautes Bott 1959 : 995, pl. 1, figs 1-6; 1969: 359; 1970: 23. Louisea Cumberlidge 1994 : 123; 1999 : 226; Ng et al. 2008 : 169 (list). Type species. Globonautes macropus edeaensis Bott, 1969, by original designation; gender feminine. Diagnosis. Amended from Cumberlidge (1994 , 1999 ). Carapace ovoid, high (CH/FW 1.28-2.12, N = 57) with faint urogastric groove ( Figs 2 a-d , 3 a-d ). Postfrontal crest detectable (either prominent or faint), but meeting anterolateral margins of carapace ( Fig. 7 a-d ). Exorbital, intermediate teeth small, but detectable; epibranchial tooth minute, almost undetectable ( Figs 4 , 7 a-d ). Medial inferior margin of merus of cheliped with large jagged tooth one-third from distal margin, followed by numerous distinct smaller teeth decreasing in size proximally ( Fig. 9 a-d ). Third maxilliped exopod completely lacking flagellum; third maxilliped ischium with vertical groove ( Fig. 14 a-d ). Mandibular palp 2 segmented; terminal segment (TS) bilobed, with large anterior lobe (0.5-0.8 x TS length) ( Fig. 15 a-d ). G1 highly stout, distinctly sinuous; terminal article (TA) short, about one quarter length of subterminal segment (SS) (TA/SS 0.22-0.29), directed outwards at 45° angle to longitudinal axis of G1; SS, inverted funnel-shaped, proximally distinctly broad, abruptly narrow, slim, distal two-thirds tube-like; G1SS stout, tapering slightly from wide basal margin to relatively wide distal margin (0.6 x SS basal margin), dorsal face with broad dorsal membrane (maximum width 0.1 x SS length) at TA/SS junction ( Figs 11 a-d , 12 a-d ). G2TA long (TA/SS 0.40-0.44), flagellum-like, almost as long as G2SS ( Fig. 13 a-d ). Small species (CW 14-22 mm in adults). Figure 2. Four species of Louisea endemic to southwestern Cameroon, whole animal, dorsal view. a Largest adult male (CW 17.5 mm) of L. edeaensis from Lake Ossa wetland complex (ZMB Crust. 26930) (missing right cheliped) b largest adult male (CW 16.2 mm) of L. balssi from Man's Crater Lake Manengouba (ZMB Crust. 30319) (missing left p5) (' Mvogo Ndongo et al. 2018 : fig. 1', www.mapress.com/j/zt) c largest adult male, holotype (CW 18.1 mm) of L. yabassi sp. nov. from Yabassi (ZMB Crust. 21575) (missing left p2-p5, and right cheliped and p2, p3) d largest adult male, holotype (CW 20.0 mm) of L. nkongsamba sp. nov. from Mt. Nlonako (ZMB Crust. 31618). Scale bars: 8 mm ( a ), 9 mm ( b ), 8.30 mm ( c ), 17 mm ( d ). Figure 3. Four species of Louisea endemic to southwestern Cameroon, whole animal, dorsal view. a Second largest adult male (CW 16.1 mm) of L. edeaensis from Lake Ossa wetland complex (ZMB Crust. 30335) (missing left p4) b second largest adult male (CW 14.8 mm) of L. balssi from Man's Crater Lake Manengouba (ZMB Crust. 30319) (missing left p4 and right p2) c subadult male, paratype (CW 13.8 mm) of L. yabassi sp. nov. from Yabassi (ZMB Crust. 21575) (missing left p2-p4, and right cheliped and p2-p5) d second largest adult male (CW 18.38 mm) of L. nkongsamba sp. nov. from Mt. Nlonako (ZMB Crust. 31618). Scale bars: 12.42 mm ( a ), 10 mm ( b ), 8.42 mm ( c ), 11.63 mm ( d ). Figure 4. Four species of Louisea endemic to southwestern Cameroon, carapace, dorsal view. a Largest adult male, holotype (CW 20.0 mm) of L. nkongsamba sp. nov. from Mt. Nlonako (ZMB Crust. 31618) b second largest adult male (CW 14.8 mm) of L. balssi from Man's Crater Lake Manengouba (ZMB Crust. 30319) c second largest adult male (CW 16.1 mm) of L. edeaensis from Lake Ossa wetland complex (ZMB Crust. 30335) d adult male, holotype (CW 18.1 mm) of L. yabassi sp. nov. from Yabassi (ZMB Crust. 21575). Scale bars: 9.1 mm ( a ), 7.25 mm ( b ), 7.90 mm ( c ), 8.62 mm ( d ). Distribution. Louisea is endemic to southern Cameroon ( Cumberlidge 1994 , 1999 ) ( Fig. 1 ). Louisea edeaensis is known from Yaounde, Edea, and the Lake Ossa faunal reserve, while L. balssi is known from the Bakossi region at Barombi Mbo near Kumba and from Manengouba Ecological Reserve ( Cumberlidge 1994 , 1999 , Mvogo Ndongo et al. 2017a , 2018 ). Louisea nkongsamba sp. nov. is known from Mt. Nlonako Ecological Reserve at Nkongsamba, while Louisea yabassi sp. nov. is from Yabassi. Remarks. Cumberlidge (1994 , 1999 ) provided the diagnostic characters of Louisea based mainly on the male holotype of L. edeaensis , because L. balssi was only known then from a juvenile male. The revision of the diagnostic characters for this genus is based on our examinations of adult males of all four species included here ( L. edeaensis , L. balssi , L. nkongsamba sp. nov., and L. yabassi sp. nov.). The amended character descriptions are also used to compare Louisea with other potamonautid genera. The bilobed terminal segment of the mandibular palp of Louisea is unusual, and it sets this genus apart from most genera in the Potamonautinae that typically possess a simple mandibular palp (i.e., with no additional anterior lobe) ( Cumberlidge 1999 ; Cumberlidge et al. 1999; Cumberlidge and Reed 2003). This is true for Erimetopus Rathbun, 1894 and Platythelphusa A. Milne-Edwards, 1887, and all but one species of Potamonautes MacLeay, 1838 [ P. brincki (Bott, 1960) being the exception], most species of Sudanonautes Bott, 1955 [except for S. floweri (de Man, 1901) and S. orthostylis Bott, 1955], and most species of Liberonautes Bott, 1955 ( Cumberlidge 1999 ). It should be noted that in those potamonautine species without a simple mandibular palp, the anterior lobe is little more than a hard ledge at the junction between the segments, rather than a true lobe shape ( Cumberlidge 1999 ). The terminal segment of the mandibular palp of Louisea is distinctly bilobed (with an anterior lobe 0.6 x the terminal segment length) and is superficially similar to the mandibular palps of Afrithelphusa Bott, 1969 and Globonautes (the two West African genera assigned to the Deckeniinae Ortmann, 1897, but the mandibular palp of the each of the latter two genera has a larger anterior lobe that is subequal to the posterior lobe ( Fig. 15 a-d ; Cumberlidge 1999 : fig. 48 A-C ). The lack of a flagellum on the exopod of the third maxilliped in Louisea is rarely seen in other species of the Potamonautinae , and most of the members of this subfamily typically possess a long flagellum on the third maxilliped exopod ( Cumberlidge 1999 ). The exceptions to this are the species of Buea and Potamonemus , and Liberonautes grandbassa Cumberlidge, 1999 and L. lugbe Cumberlidge, 1999 ( Cumberlidge and Clark 1992 ; Cumberlidge 1993 , 1999 ; Cumberlidge et al. 2019 ). The lack of a flagellum on the exopod of the third maxilliped of Louisea is also shared with species of the Deckeniinae ( Afrithelphusa , Globonautes , and Madagapotamon humberti Bott, 1965) ( Cumberlidge 1999 ; Cumberlidge et al. 2008 ). Louisea can also be distinguished from the West African Deckeniinae genera Afrithelphusa and Globonautes by characters of the gonopods (G1TA shape and G2TA length), the presence or absence of an intermediate tooth between the exorbital and epibranchial teeth ( Cumberlidge 1999 ), and by molecular evidence ( Daniels et al. 2015 ; Mvogo Ndongo et al. 2017c ).