Comparative analyses of complete mitochondrial genomes of four sillaginids fish (Perciformes: Sillaginidae) and phylogenetic implications

Abstract

Sillago muktijoddhai, S. mengjialensis, S. sihama and Sillaginops macrolepis (Perciformes, Sillaginidae) are common coastal sand borers. The first three species are found in the Northeastern Indian Ocean, and the fourth one is located in the Western Central Pacific Ocean only. Molecular data applying in the prior investigations on systematics and phylogenetic relationships were not only incomplete but also uncertain for these fishes. This study sequenced their complete mitochondrial genomes using Sanger Dideoxy DNA sequencing for the first time. Their complete mitochondrial genome was a circular molecule of 17,022, 16,624, 16,825 and 16,502bp in length for S. muktijoddhai, S. mengjialensis, S. sihama and Sillaginops macrolepis, respectively. Most protein-coding genes (PCGs) were initiated with the typical ATG codon and terminated with the TAA or TAG codon and the incomplete termination codon T/TA could be detected in the four species. The majority of AT-skew and GC-skew values of the entire mitogenomes among the four species were negative. The Ka/Ks ratio analyses indicated 13 PCGs were suffering strong purifying selection. In the phylogenetic analysis, S. muktijoddhai, S. mengjialensis, and S. sihama were placed with relative species of the genus Sillago supporting morphological phylogeny. However, S. macrolepis was situated in the clade of genus Sillago that contrasted to morphological phylogeny. Divergence time analysis showed that Sillaginidae species diverged around 61 million years ago. Bangladesh J. Sci. Ind. Res. 59(2), 87-104, 2024