Friday, February 17, 2012

[Ichthyology • 2011] Tonlesapia amnica | Mekong Delta dragonet • a new species of dragonet (Teleostei: Callionymidae) from the Mekong delta, southern Vietnam

Tonlesapia amnica, a new species of dragonet lacking a first dorsal fin, is described from the Mekong River delta in southern Vietnam. It can be distinguished from its sole 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).
Key words: Vietnam, Perciformes, Callionymoidei, Southeast Asia

Members of the family Callionymidae are benthic marine fishes with a largely circumtropical distribution, found in a variety of coastal habitats at depths of up to 900 m (Fricke, 2002). There are more than 180 species in the family (Fricke, 2002), with the bulk of its diversity in the Indo-Pacific region. The phylogeny of callionymids is not well understood: there has been only one such study (Nakabo, 1983). Furthermore, differences in the genus-level classifications of the Callionymidae exist (Fricke 1983, 2002; Nakabo, 1982).

Fishes collected during a recent ichthyofaunal survey in the Mekong River delta, southern Vietnam by the second author included a callionymid species lacking a first dorsal fin. Although initially believed to be Tonlesapia tsukawakii Motomura & Mukai, 2006, a species lacking the first dorsal fin recently described from the Mekong River drainage, close examination of the Vietnamese material revealed differences that showed it to be distinct. The description of this material as Tonlesapia amnica, new species, forms the basis of this study.

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