DNA barcoding of feral tilapias in Philippine lakes

Abstract

Tilapia (Oreochromis mossambicus) was first introduced to the Philippines in 1950 for aquaculture. Since then, other species of tilapia have been introduced to the country and some of them (mainly Oreochromis niloticus) have become established in lakes and other water bodies. In this study, DNA barcoding using the mitochondrial cytochrome c oxidase subunit I (COI) gene was done to assess the reliability of morphological identification and the degree of introgression among feral tilapias (Oreochromis spp.) in seven major Philippine lakes, namely Laguna de Bay, Lake Lanao, Taal Lake, Lake Mainit, Lake Naujan, Lake Bato, and Lake Buhi. Specimens were also collected from a private hatchery in Sual, Pangasinan to serve as reference. Morphological traits, Nucleotide BLAST (BLASTn), and Translated BLAST (BLASTx) analyses were used to classify the specimens. A Neighbor-Joining tree was constructed using the Kimura 2-Parameter method, incorporating 66 COI sequences generated from the study and 20 additional reference sequences obtained from GenBank. Three Oreochromis clusters were obtained and were classified as the O. niloticus group, O. mossambicus group, and O. aureus group, with bootstrap support values of 99%, 74%, and 99%, respectively. The mean K2P genetic distances within each group were 0.008%, 0.959%, and 0.086%, respectively. The clustering of COI sequences generated from this study corresponded with the results of the BLASTn analysis. Oreochromis hybrids were also found in all the lakes. The study highlights the usefulness of DNA barcoding for molecular identification and detection of introgressed individuals, with potential applications in management of feral stocks.

Keywords:

• Cichlid
• COI
• DNA barcoding
• Philippine lakes
• Tilapia

Acknowledgments

The authors wish to thank the Philippine Department of Agriculture – Bureau of Fisheries and Aquatic Resources (DA-BFAR) for the Gratuitous Permit; and the Municipal Agriculturists (Cynthia Buen and Romeo Cruz), City and Provincial Fishery Officers (Alejandro Pili Jr., Joseph L. Estanislao, Val Alfred R. Viana, Jefrey E. Naïve, and Saida Tomadung), fisheries enumerators and BFAR personnel (Jocelyn Castro, Rosel Sansolis, and Marciano Ariel B. Yber) and private individuals (Dr Jobert Toledo, Israel Lobarbio, Leonardo E. Matienzo, and Jessie I. Morales) for assistance in sampling. They would also like to thank Micah Elayda, Rachel Joanne Pomer, John Robert Orias, Marco Philip Serafica, and John Carlos del Pozo for technical assistance. They also wish to thank Dr Dalisay D. G. Fernandez and Dr Norida Pantas-Samson of DOST-PCAARRD.

Declaration of interest

The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper. The authors wish to thank the Department of Science and Technology – Philippine Council for Agriculture, Aquatic and Natural Resources Research and Development (DOST-PCAARRD) for funding.