Louisea Cumberlidge, 1994

Mvogo Ndongo, Pierre A., von Rintelen, Thomas & Cumberlidge, Neil, 2019, 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, ZooKeys 881, pp. 135-164 : 135

publication ID	https://dx.doi.org/10.3897/zookeys.881.36744
publication LSID	lsid:zoobank.org:pub:B058CA15-6A3D-41A1-9ADF-D00384234D8E
persistent identifier	https://treatment.plazi.org/id/D44FD7D8-9485-5BB4-867F-140EADCA8612
treatment provided by	ZooKeys by Pensoft
scientific name	Louisea Cumberlidge, 1994
status

Treatment

Genus Louisea Cumberlidge, 1994 View in CoL

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 View Figure 2 , 3 a–d View Figure 3 ). Postfrontal crest detectable (either prominent or faint), but meeting anterolateral margins of carapace ( Fig. 7 a–d View Figure 7 ). Exorbital, intermediate teeth small, but detectable; epibranchial tooth minute, almost undetectable ( Figs 4 View Figure 4 , 7 a–d View Figure 7 ). 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 View Figure 9 ). Third maxilliped exopod completely lacking flagellum; third maxilliped ischium with vertical groove ( Fig. 14 a–d View Figure 14 ). Mandibular palp 2 segmented; terminal segment (TS) bilobed, with large anterior lobe (0.5-0.8 × TS length) ( Fig. 15 a–d View Figure 15 ). 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 × SS basal margin), dorsal face with broad dorsal membrane (maximum width 0.1 × SS length) at TA/SS junction ( Figs 11 a–d View Figure 11 , 12 a–d View Figure 12 ). G2TA long (TA/SS 0.40-0.44), flagellum-like, almost as long as G2SS ( Fig. 13 a–d View Figure 13 ). Small species (CW 14-22 mm in adults).

Distribution.

Louisea is endemic to southern Cameroon ( Cumberlidge 1994, 1999) ( Fig. 1 View Figure 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 × 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 View Figure 15 ; 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).