Tonlesapia amnica

description

Description. D 2 viii, 1 * (21) or ix, 1 (1); A vi, 1 (2) or vii, 1 * (22); P 1 i, 12, i (6), i, 12, ii (1), ii, 12, ii (1), i, 13, i * (6), i, 14, i (4), i, 15, i (3) or i, 17, i (1); P 2 i, 5 (22); C i, 6, ii (22). Biometric data as in Table 1. Body elongate, slightly depressed. Head moderately depressed. Snout sloping evenly and moderately. Dorsal body profile somewhat horizontal to base of second dorsal fin, sloping gradually ventrally from there to end of caudal peduncle. Ventral body profile horizontal to base of first anal-fin ray, sloping very gently dorsally from there to end of caudal peduncle. Eye large. Interorbital space narrow. Gill opening small, ovoid, located midway between posteriormost point of orbit and base of first pectoral-fin ray. Preopercular spine without antrorse spur at base, with posterior main tip curved dorsally, and 3 – 7 curved points along dorsal margin; spine covered by thin skin along dorsal margin. Upper jaw protractile, posterior end reaching to midway between anterior tip of mesethmoid and anteriormost point of orbit. Single nostril on snout. Urogenital papilla conical, males with slightly longer papilla than females. Lateral line extending fr

Tonlesapia amnica, a new species of dragonet (Teleostei: Callionymidae) from the Mekong delta

diagnosis

Diagnosis. Tonlesapia amnica differs from its only congener, T. tsukawakii, in having the infraorbital canal extending beyond (vs. not reaching) ventral margin of orbit, a more slender body (7.2 – 13.5 % SL vs. 14.3 – 15.0) and caudal peduncle (4.4 – 5.2 % SL vs. 5.1 – 6.3), a smaller eye (6.5 – 8.3 % SL vs. 8.7 – 9.2) and more dorsal-fin rays (9 – 10 vs. 8).

Tonlesapia amnica, a new species of dragonet (Teleostei: Callionymidae) from the Mekong delta

distribution

Distribution and habitat. Known from the Mekong River delta in southern Vietnam (Fig. 4). The Song Hau Giang (a branch of the Mekong River also known as the Bassac River) at the type locality of C. amnica is fairly clear, slow flowing (current about 0.2 ms - 1) and wide (2 km) with a sand and silt bottom. Other species of fish obtained at this locality included: Clupeoides borneensis (Clupeidae), Corica soborna (Clupeidae), Coilia lindmani (Engraulidae), Thryssocypris tonlesapensis (Cyprinidae), Acantopsis sp. (Cobitidae), Kryptopterus geminus (Siluridae), Pangasius mekongensis (Pangasiidae), Akysis similis (Akysidae), Plotosus canius (Plotosidae), Boesemania microlepis (Sciaenidae), Polynemus bidentatus (Polynemidae), Eleotris melanosoma (Eleotrididae), Redigobius chrysosoma (Gobiidae), Stenogobius mekongensis (Gobiidae), Taenioides cirratus (Gobiidae), Brachirus elongatus (Soleidae), Synaptura panoides (Soleidae), Cynoglossus gracilis (Cynoglossidae) and Cynoglossus puncticeps (Cynoglossidae). Tonlesapia amnica has also been collected from brackish habitats and is the third species of Indo-Pacific callionymid known to inhabit freshwaters (the other species being Callionymus fluvi

Tonlesapia amnica, a new species of dragonet (Teleostei: Callionymidae) from the Mekong delta

etymology

Etymology. The specific name amnica is a feminine Latin adjective meaning pertaining to a river. The name is used in reference to the riverine habitat of this species.

Tonlesapia amnica, a new species of dragonet (Teleostei: Callionymidae) from the Mekong delta