Speolabeo, Kottelat, Maurice, 2017

Kottelat, Maurice, 2017, Speolabeo, a new genus name for the cave fish Bangana musaei (Teleostei: Cyprinidae), Zootaxa 4254 (4), pp. 493-499 : 497-498

Speolabeo , new genus

Type species. Bangana musaei Kottelat & Steiner, 2011 .

Etymology. The name is formed on the classical Greek noun σπέΟς (speos), which means cave, cavern, excavation; and labeo, originally a Latin noun meaning a man with thick lips, which in ichthyology became a genus name, then a vernacular name as well as the base of the family-group name as a subfamily Labeoninae or tribe Labeonini. Gender masculine.

Diagnosis. The diagnostic characters of the genus are the same as those of the only included species. Speolabeo musaei is a cave fish showing characters common to many hypogean fishes (and other animals), which are unique among the species earlier placed in Bangana s.l.: absence of eyes and whitish colour (pinkish in life) due to the lack of pigmentation. These characters are cave adaptations that have appeared in parallel in numerous fish species living in caves, in aquifers, in crevices, under stones as well as in deep rapids ( Proudlove, 2006). They are useful to identify the genus, but by themselves do not justify the recognition of a distinct genus (see, e.g., Greenwood, 1976, Banister & Bunni, 1980).

However, there are other characters not related to adaptation to life in hypogean habitats that distinguish Speolabeo from Bangana , Altigena and the 'B.' lemassoni -group: the dorsal fin has 7–8½ branched dorsal-fin rays (vs. 10–12½); the origin of the pelvic fin is located at the vertical between the first unbranched and first branched dorsal-fin rays (vs. at the vertical through 3rd to 6th branched rays); there are no tubercles on the snout (vs. tubercles present); the edge of the upper jaw is distinct, very narrow, adnate to the upper lip and separated from it by a narrow and very shallow furrow (vs. upper jaw entirely enclosed in upper lip); the distal edge of the dorsal fin is straight or slightly concave (vs. conspicuously concave in Altigena and Bangana ); 35–37 lateral-line scales (vs. 40–47 in the 'B.' lemassoni -group, 40–43 in Bangana ). The postlabial groove is restricted to the corner of the mouth (vs. complete in Altigena , medially interrupted in Bangana and the 'B.' lemassoni -group); however, in CMK 26632, two small specimens from a separate cave, a very shallow groove is present. This could be geographical variation or related to the smaller size. Also, the smaller specimens were fixed in ethanol, and the soft tissues have collapsed and are not in an optimal condition for the description of soft anatomy.

Zhang & Chen (2006) diagnosed Bangana s.l. with, among others, the following characters related to the mouth morphology: the upper jaw is entirely enclosed in the upper lip, whose median part is covered by the rostral fold; the rostral fold is thick, pendulous, separated from the upper lip by a deep groove, not continuous with the lower lip; the upper lip is continuous with the lower lip; the lower lip is separated from the lower jaw by a groove, its anterior margin is free and has numerous papillae on the dorsal surface; the lower jaw is cornified, with a sharp edge. All these structures are present in Speolabeo , except that the upper jaw is not enclosed in the upper lip but adnate behind it (a condition overlooked by Kottelat & Steiner, 2011). The rostral fold is present but, unlike in Bangana , Altigena and the 'B.' lemassoni group, it is not thick and fleshy. The upper and lower lips are continuous in Speolabeo . The lower lip is separated from the lower jaw by a shallow groove and leaves most of the lower jaw exposed; the dorsal surface of the lip is narrow, not covered by papillae, and its anterior margin is crenulated. The median part of the lower lip is very thin and cannot easily be distinguished from the skin of the gular area; if it were not for the crenulated edge and the groove separating it from the jaw, the lip would appear as if widely interrupted and restricted to the corners of the mouth. The lower jaw has a cornified but blunt edge.

Remarks. Since its original description, S. musaei has been observed and collected in other caves in the Khammouan Karst near the type locality (H. Steiner, pers. comm.). These additional specimens do not show differences from the original description except as noted under the diagnosis for the postlabial groove. For the time being it does not seem worthwhile to speculate on the possible phylogenetic relationships of Speolabeo .

Speolabeo musaei was originally placed in Bangana by default, because of the inability to place it in a known genus and the unwillingness to establish a distinct genus for a species whose most salient characters were related to its specialised habitat. However, a number of the characters used in the diagnosis (especially the relative positions of the dorsal and pelvic fins and the number of dorsal-fin rays) cannot be the result of cave adaptations. After the 'dismantling' of Bangana s.l., based on external characters 'B.' musaei cannot be placed in any of the resulting genera, or in any other named labeonine genera. It is therefore recognised here as a distinct genus; keeping it in any of the mentioned genera would be just as artificial as its placement earlier in Bangana s.l.

In some cases the relationships of a cave species with one or more epigean species are obvious (e.g. Astyanax jordani , see Proudlove, 2006). In other cases there is apparently no closely related epigean species (at least not based on external characters) (e.g. Cryptotora thamicola, Kottelat, 1988, 1998b ; Draconectes narinosus, Kottelat, 2012 ). Noteworthy is that two other fish species are known from the caves of the Khammouan Karst, for both of which it has not been possible to identify close relatives. The possible relationships of Troglocyclocheilus khammouanensis Kottelat & Bréhier, 1999 are unclear. Schistura kaysonei Vidthayanon & Jaruthanin, 2002 has characters such as a reduced number of caudal-fin rays and a nasal barbel unknown in any Schistura (and other Nemacheilidae ) of the Xe Bangfai and adjacent drainages ( Kottelat, 1998a, 2000, 2001, 2016b, unpubl. obs.). The Khammouan Karst is continued across the border eastwards in Vietnam; this area is poorly known ichthyologically and relatives of Speolabeo musaei , Troglocyclocheilus khammouanensis and Schistura kaysonei may await discovery in this system.

Material examined. Speolabeo musaei , CMK 20111, 1 paratype, 70.1 mm SL; CMK 26632, 2, 41.5–57.7 mm SL; Laos: Xe Bangfai , caves near entrance of tunnel.— Bangana devdevi , CMK 16257, 1; Thailand: Salween River .— Altigena elegans , CMK 191864, 4 ; Laos: Nam Theun watershed .— Altigena lippa , CMK 21050, 5; Laos: Nam Ou watershed .— 'Bangana' aff. lemassoni, CMK 25784, 1 , CMK 25804, 1; Laos: Nam Ma drainage.— Incisilabeo behri , CMK 15882, 1; Laos: Mekong at Khone Falls . Additional material listed in Kottelat (1998) and Kottelat & Steiner (2011).