Evolutional scenario of the genus Anguilla based on the analysis of multiple genes

Abstract

The life history of the catadromous eel, the gen us Anguilla , is very complicated and unique . According to Ege (1939), Castle and Williamson (1974), and Watanabe (2001), anguillid eels were classified into 18 species and subspecies based on the skin color, morphometric characters, dentition , and vertebral counts. The eel spawns in the deep tropical/subtropical ocean . Their leaf-like larvae, leptocephali , are transported and dispersed by oceanic currents from spawning ground, and metamorphose into glass eels on continental shelf after several months of drifting. Glass eels become pigmented elvers i n estuary and grow up to be yellow eels i n freshwater. Eels metamorphose from yellow to silver form before spawning migration . Silver eels migrate long distance back to their original bi11hplace to spawn and die (Tesch, 1977 ; Tsukamoto , 1992; Liao et al.,1999). The life cycle of the anguillid eels forms a species-specific "migration loop "(Tsukamoto and Aoyama , 1998 ; Tsukamoto, 1999) Recent progress in molecular technology provides powerful tools for the study of phylogenetic evolution between and with i n taxa. Aoyama et al. (1996) and Tsukamoto and Aoyama (1998) firstly presented the molecular phylogeny of the anguillid species based on the mitochondrial cytochrome b gene. Moreover, Aoyama (1999; 2001) further constructed the taxonomy tree of the gen us Anguilla by 16S rRNA+ cytochrome b genes. In this study, we analyses of the mitochondrial 12S rRNA , 16S rRNA, and cytochrome b genes, together with those of the genomic GTH 11-P subunit DNAs of 8 anguillid eels or analyses of the mitochondrial 12S rRNA, 16S rRNA, cytochrome b genes, as well as the genomic GTH 11-beta subunit DNAs of 8 anguillid eels, and constructed the phylogenetic tree based on them to further clarify the taxonomy of the genus Anguilla.