Molecular systematics of the thornfishes genera Terapon and Pelates (Perciformes : Teraponidae) with reference to the new genus Pseudoterapon

The aim of this study is to clarify whether the systematic status of 3 exte rnally similar thornfishes can be resolved to posit them at specific or gen eric levels by using allozyme electrophoresis and partial 12S rRNA sequence s of mitochondrial DNA. Three externally similar thornfishes, Terapon jarbu a, 7 theraps, and Pelates quadrilineatus, can be distinguished by several f ixed isozyme loci: IDHP-2* LDH-A* LDH-B* MDH-1* MDH-2* SDH-1 SOD-1*, SOD-2* , and SOD-3*. Nei's unbiased genetic identity of isozymes ranged 0.321-0.45 4 (or distance 0.790-1.137), and the nucleotide base difference of mtDNA ra nged 7.3%-10.9% among the 3 species, enabling them to posit as 3 separate g enera. Nei's genetic similarity between congeneric T. theraps and T. jarbua (0.441) is very low. The position of T. theraps with T. jarbua on the tree s constructed from both isozyme and mtDNA data show similar profiles of gro uping on separate nodes. This may support 7. theraps being removed from the genus Terapon as an independent new genus, Pseudoterapon. The main diagnos tic morphological characters distinguishing Pseudoterapon from Terapon are: larger scales, absence of teeth on vomer and palatines, and horizontal dar k stripes on body sides.