Malihkaia, Maurice Kottelat, 2017

Maurice Kottelat, 2017, A new genus and three new species of nemacheilid loaches from northern Irrawaddy drainage, Myanmar (Teleostei: Cypriniformes), Raffles Bulletin of Zoology 65, pp. 80-99 : 81-84

Malihkaia , new genus

Type species. Malihkaia aligera , new species ( Figs. 1–2 ).

Diagnosis. Malihkaia is distinguished from all other genera of nemacheilids by the unique morphology of the lips and the unique pectoral fn sexual dimorphism. Lips thick, with numerous, closely set, deep furrows ( Fig. 3 ). Upper lip with a small median notch, with transverse furrows on its whole length, edge crenulated. Lower lip with a median interruption; with transverse furrows on its whole length, edge crenulated.

In the male, the pectoral fn is strongly falcate ( Fig. 2 ). The unbranched ray is fexible and shaped as in other species of Nemacheilidae . The frst branched ray is rigid, arched and curled upwards ( Fig. 4 ). It is about 5 times wider than the other branched rays. It is fattened dorso-ventrally and very elongate, reaching beyond pelvic-fn base. It is frst branched at about midlength. The posterior main branch is thicker than the anterior main branch; it is branched again twice, the third branching about at distal one-sixth of the ray. The anterior branch is branched again only once, in a position intermediate to that of branching points 2 and 3 of posterior main branch. There is no membrane between all the branches and sub-branches, but there is a membrane around the tip of the ray.

The second and third branched rays are very slender, branched only at their distal third, the anterior branch is thicker than the posterior one and it is branched again once; the posterior branch has no sub-branches. The membrane between the branches is very narrow. The spaces and relative ‘depth’ of the branching increase regularly in the following rays. The fourth and following branched rays have two branches that are each branched once. There is some variation in the branching apparently related to size and small injuries; the above is based on intact fns.

The lower surface of the unbranched ray and the unbranched part of frst branched ray and the membrane between the three frst rays are covered by an unculiferous pad ( Conway et al., 2012), thickest under the frst branched ray. There are also pads under the membranes between the other rays, but less developed. There also are granulations (unculi?) on the dorsal surface of the rays and thickened tissue on the membranes.

In females, the pectoral fn is rounded; there are unculiferous pads under the rays, thickest under the unbranched and frst branched ones, decreasing in extant and thickness posteriorly. The unbranched ray is thicker than the following rays and rigid; dorsally, the membrane between the frst two rays is thickened. The frst branched ray is thickened but fexible, round in cross-section, thicker than the following rays; the anterior branch is unbranched. The posterior branch is branched once, the anterior sub-branch is unbranched and the posterior one branched again. In the second branched ray, the anterior branch is unbranched and the posterior branch is branched again. The remaining rays are all branched twice as in other nemacheilids. There is some little variation in the branching, related with small injuries and regrowth; the above is based on one intact fn on each female.

In both sexes, in both pelvic and pectoral fns, the anterior edge of the unbranched ray has a thick tissue cover. In both sexes, the pelvic fn has thickened tissue on membranes between the unbranched ray and branched rays 1–3, dorsally and ventrally, also covering part of these rays ventrally.

Additional characters useful to distinguish the genus are: processus dentiformis present; suborbital fap present in males; 8½ branched dorsal-fn rays; 9+8 branched caudal-fn rays; axillary pelvic lobe present; anus situated about 1.5–2 eye diameter in front of anal fn; body entirely scaled; lateral line complete; air bladder without posterior chamber; body with 9–12 bars extending from dorsal midline to level of pectoral fn, bars of quite regular width and shape in front of dorsal fin, less regular posteriorly, much wider than interspaces; and black mark at caudal-fn base made of a more or less squarish blotch in middle of base, a more or less triangular blotch over dorsal procurrent rays, fainter pigments over base of uppermost and lowermost 4–6 principal rays of caudal fn.

Etymology. Named for Mali Hka River, where the type species was discovered. Gender feminine.

Remarks. The deeply furrowed lower lip of Malihkaia aligera is unique in South and Southeast Asian Nemacheilidae . Acanthocobitis (including Paracanthocobitis , see Kottelat, 2012b: 74, 2013: 198) has papillated lips ( Kottelat, 1990, 2012a). On the upper lip, the papillae are organised in several rows; on the lower lip there is a broad median interruption and, on each side, a widened, strongly papillated pad, covered by papillae. Species of Acanthocobitis also have a very different colour pattern, made of obliquely organised bars, usually of irregular shape and organisation. All species of Acanthocobitis have a small black spot (sometime ocellated) at the upper extremity of the base of the caudal fn. Finally, species of Acanthocobitis have a longer dorsal fn, with 9–18½ branched rays.

In Nemacheilidae , the deeply furrowed lips are otherwise known only in some species of Labiatophysa , Triplophysa and Tarimichthys , all endemic to the Tibetan plateau, the Tarim and adjacent endorheic basins in China, Kazakhstan and Kyrgyzstan, and adjacent waters. These genera are distinguished, among others, by the absence of scales (most species), males with densely set unculi on the side of the head below the eye and on the dorsal surface of anterior pectoral-fn rays ( Prokofev, 2004, 2010).

Cobitiforms have developed a great variety of sexual dimorphism, but most of it associated with the pectoral fns and involving thickening and modifcation of rays (see, e.g., Šlechtová et al., 2008 for sexual dimorphism in Cobitis and related genera; Kottelat & Lim, 1992 for Lepidocephalichthys ; Kottelat & Tan, 2008 for Kottelatlimia and Acantopsis ; Kottelat, 1990 for Indochinese Nemacheilidae ; Bohlen & Šlechtová, 2011 for Pteronemacheilus ); sexual dimorphism may also involve, for example, thickening of parts of the body (e.g., in Sabanejewia, Kottelat & Freyhof, 2007 ) or vertical torsion of the caudal peduncle (in Microcobitis ; pers. obs., unpubl.). The modifed pectoral fn of male M. aligera seems unique in Nemacheilidae but is very reminiscent of what is observed in some Cobitidae , especially species of Acantopsis . In Acantopsis , the branches of the frst branched ray are in contact and there is no membrane between them and the ray is covered by a dense layer of unculi (pers. obs.; Kottelat & Tan, 2008). In Kottelatlimia , the frst branched ray is branched only at the tip and may appear as an unbranched ray ( Kottelat & Tan, 2008). A curled pectoral fn in males is observed in Cobitidae in Acantopsis and Pangio (e.g., Kottelat & Tan, 2008; Kottelat & Lim, 1993) but has not been reported in Nemacheilidae before.

Figures

Fig. 1. Malihkaia aligera, MHNG 2766.051, holotype, male, 65.7 mm SL; Myanmar: Irrawaddy drainage; Mali Hka River near Putao.

Fig. 2. Malihkaia aligera, CMK 25508, paratypes; a, male, 73.0 mm SL; b, female, 77.2 mm SL; Myanmar: Irrawaddy drainage: Mali Hka River near Putao.

Fig. 3. Malihkaia aligera, CMK 25508, 73.0 mm SL; ventral view of head.

Fig. 4. Malihkaia aligera, CMK 25508, 73.0 mm SL; left pectoral fn of male; dorsal (above) and ventral (below) view. Extremity of fourth branched ray damaged.