Louisea yabassi, Mvogo Ndongo, Pierre A., von Rintelen, Thomas & Cumberlidge, Neil, 2019

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/FA6DE8AD-B833-415C-95C7-47287F3C6158
taxon LSID	lsid:zoobank.org:act:FA6DE8AD-B833-415C-95C7-47287F3C6158
treatment provided by	ZooKeys by Pensoft
scientific name	Louisea yabassi
status	sp. nov.

Treatment

Louisea yabassi sp. nov. Figs 2c View Figure 2 , 3c View Figure 3 , 4d View Figure 4 , 5c View Figure 5 , 6c View Figure 6 , 7c View Figure 7 , 8e, f View Figure 8 , 9c View Figure 9 , 10c View Figure 10 , 11c View Figure 11 , 12c View Figure 12 , 13c View Figure 13 , 14c View Figure 14 , 15c View Figure 15

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 View Figure 3 ); exorbital, intermediate teeth large, triangular; epibranchial tooth undetectable ( Figs 4c View Figure 4 , 7c View Figure 7 ). Vertical sulcus on carapace branchiostegal wall curving backward to meet anterolateral margin at epibranchial tooth ( Fig. 6c View Figure 6 ). Mandibular palp bi-segmented; terminal segment (TS) bilobed, with large distinct anterior lobe 0.6 × terminal segment length ( Fig. 15c View Figure 15 ). Third maxilliped ischium with distinct vertical groove ( Fig. 14c View Figure 14 ). Episternal sulci s4/e4, s5/e5, s6/e6 faint or missing, s7/e7 complete ( Fig. 5c View Figure 5 ). 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 View Figure 8 ); propodus of major cheliped with two large proximal teeth, large medial tooth, small distal tooth ( Fig. 8e View Figure 8 ); cheliped carpus inner margin with long, broad distal tooth, relatively narrow, subequal proximal tooth ( Fig. 10c View Figure 10 ). 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 View Figure 11 , 12c View Figure 12 ). G1SS tapering slightly from broad basal margin to relatively wide distal margin (0.5 × SS basal margin); dorsal face with broad dorsal membrane (maximum width 0.1 × SS length) at TA/SS junction ( Fig. 11c View Figure 11 ). G2TA long (TA/SS 0.44), flagellum-like, almost as long as G2SS ( Fig. 13c View Figure 13 ). 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 View Figure 4 ); exorbital, intermediate teeth large, triangular; epibranchial tooth undetectable ( Figs 4c View Figure 4 , 7c View Figure 7 ). Carapace branchiostegal sidewall with vertical, longitudinal sutures dividing it into three regions (suborbital, subhepatic, pterygostomial) ( Fig. 6c View Figure 6 ); longitudinal suture beginning at respiratory opening, curving backward across sidewall dividing suborbital- and subhepatic regions from pterygostomial region ( Fig. 6c View Figure 6 ); vertical sulcus on carapace branchiostegal wall curving backward to meet anterolateral margin at epibranchial tooth ( Fig. 6c View Figure 6 ), dividing suborbital from subhepatic regions ( Fig. 6c View Figure 6 ).

Mandibular palp bi-segmented; terminal segment (TS) bilobed, with large distinct anterior lobe 0.6 × terminal segment length ( Fig. 15c View Figure 15 ). Third maxilliped exopod completely lacking flagellum; ischium with distinct vertical groove ( Fig. 14c View Figure 14 ). Sternal sulcus s2/s3 prominent, completely crossing sternum; s3/s4 incomplete, reduced to 2 short lateral notches ( Fig. 5c View Figure 5 ). Episternal sulci s4/e4, s5/e5, s6/e6 faint or missing, s7/e7 complete ( Fig. 5c View Figure 5 ).

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 View Figure 8 ); dactylus and propodus of left cheliped straight, with small teeth on occluding margin ( Fig. 8f View Figure 8 ); cheliped carpus inner margin with two pointed teeth, distal tooth large with pointed tip, proximal tooth smaller ( Fig. 10c View Figure 10 ); medial inferior margin of cheliped merus with large jagged distal tooth followed by numerous distinct smaller teeth ( Fig. 9c View Figure 9 ).

Male pleon triangular, sides not indented with small setae; telson (a7) rounded at distal margin ( Fig. 5c View Figure 5 ). 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 View Figure 11 , 12c View Figure 12 ). G1SS tapering slightly from broad basal margin to relatively wide distal margin (0.5 × 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 View Figure 12 ); dorsal face with broad dorsal membrane (maximum width 0.1 × SS length) at TA/SS junction ( Fig. 11c View Figure 11 ). G2TA long (TA/SS 0.44), flagellum-like, almost as long as G2SS ( Fig. 13c View Figure 13 ). 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.