Complete mitochondrial genome from South American catfish Pseudoplatystoma reticulatum (Eigenmann & Eigenmann) and its impact in Siluriformes phylogenetic tree

The complete mitochondrial genome of an endemic cichlid Etroplus canarensis from Western Ghats, India (Perciformes: Cichlidae) and molecular phylogenetic analysis

BACKGROUND

The Indian endemic cichlid Etroplus canarensis (Canara pearl spot) is an endangered fish and is one among the three Indian cichlids (Etroplinae) that had a restricted distribution in the South Canara region of Karnataka, India. Despite considerable investigations, the phylogeny of Indian Cichlids and its biogeographical origin is still ambiguous and remains a question under discussion which is scrutinized based on whole mitogenomes in the present study.

METHODS AND RESULTS

We report the 16,339 bp complete mitochondrial genome of E. canarensis for the first time using the next-generation sequencing methods. Comparison of gene arrangement and genome characterization was found to commensurate with the previous reports on two Indian cichlid fishes, E. suratensis and E. maculatus. ND6 has been identified as a gene with the highest evolutionary rate and COI and COII is the most conserved gene based on p-genetic distance calculation. Substitution rate (ka/ks) was found to be very low indicating a reduced rate of evolution among subfamily Etroplinae accounting for its subsided species divergence of Indian cichlids. Phylogenetic analysis of Indian cichlids based on a combined dataset of 12 protein-coding genes representing cichlids generated high posterior probability values pillaring paraphyletic nature of Indian Malagasy lineage and monophyletic Indian genus Etroplus.

CONCLUSION

The mitogenome sequence of E. canarensis may provide fundamental molecular data useful for further researches on genetic diversity, endemicity and the conservation of this endangered freshwater fish.

Mitochondrial genome annotation and phylogenetic placement of Oreochromis andersonii and O. macrochir among the cichlids of southern Africa

Genetic characterization of southern African cichlids has not received much attention. Here, we describe the mitogenome sequences and phylogenetic positioning of Oreochromis andersonii and O. macrochir among the African cichlids. The complete mitochondrial DNA sequences were determined for O. andersonii and O. macrochir, two important aquaculture and fisheries species endemic to southern Africa. The complete mitogenome sequence lengths were 16642 bp and 16644 bp for O. andersonii and O. macrochir respectively. The general structural organization follows that of other teleost species with 13 protein-coding genes, 2 rRNAs, 22 tRNAs and a non-coding control region. Phylogenetic placement of the two species among other African cichlids was performed using Maximum Likelihood (ML) and Bayesian Markov-Chain-Monte-Carlo (MCMC). The consensus trees confirmed the relative positions of the two cichlid species with O. andersonii being very closely related to O. mossambicus and O. macrochir showing a close relation to both species. Among the 13 mitochondrial DNA protein coding genes ND6 may have evolved more rapidly and COIII was the most conserved. There are signs that ND6 may have been subjected to positive selection in order for these cichlid lineages to diversify and adapt to new environments. More work is needed to characterize the southern Africa cichlids as they are important species for capture fisheries, aquaculture development and understanding biogeographic history of African cichlids. Bio-conservation of some endangered cichlids is also essential due to the threat by invasive species.