IDENTIFICATION OF INDIGENOUS AND EXOTIC Anabas testudineus (BLOCH, 1792) THROUGH MORPHOMETRIC AND DNA BARCODING ANALYSIS

Abstract

Three populations of Anabas testudineus were found in the aquaculture of Bangladesh which belong to the same species, but not look alike. In this study, attempts were taken for identification of the variation among them by analyzing morphometrics and DNA barcode gene. Different linear measures and meristic count were analyzed. The landmark-based geometric morphometrics including 14 landmarks from each sample were analyzed by TPS software series and PAST. Fish barcode mitochondrial gene Cytochrome C Oxidase I (COI) and Cytochrome b (Cyt b) were amplified by PCR and then sequenced. The DNA sequences of COI and Cyt b genes were blasted, aligned, translated and submitted to the GenBank data base using a standalone submission programme “Bankit”. By using two genes evolutionally analyses and phylogenetic tree reconstruction were performed through MEGA. Total length and standard-length ratios, and six (out of 11) meristic counts of indigenous, Thai and Vietnamese A. testudineus showed variation. The number of caudal fin rays, number of black spot, the scales on upper lateral line, lower lateral line and from lower lateral line to anal fin were varied among them. The result of geometric morphometric study showed 94.208% variance among the populations with Eigenvalue (163.494) in principal component 1.Variation were detected among 3 female populations, with variance of 94.238%, among three male populations with a variance of 84.523%. In pairwise study, the highest variance (97.07%) were found between indigenous and Thai female populations. The highest sexual dimorphism with a variance of 96.33% were found in between Thai female and male. The UPGMA cluster analysis showed the separate cluster formation of three populations. The COI gene sequence analysis findings showed that out of the 610 consensus sites 321 (52.62%) were constant and 288 (47.21%) were variable. The transition/transverion bias (R) was 0.94. Interestingly no genetic distance was found in between A. testudineus of Thai population of the current study and the A. testudineus NCBI Thai submission. A. testudineus of Vietnamese population of the current study and the A. testudineus NCBI Vietnamese submission also showed no genetic distance. On the other hand, the highest genetic distance was found in between native and Vietnamese A. testudineus (0.098), followed by native and Thai A. testudineus (0.092), Vietnamese and Thai (0.026). Bootstrap consensus Neighbour-joining (NJ) tree revealed identical phylogenetic relationship within the population. The time tree depicted the highest divergence time 0.05 MYA in between native and Thai A. testudineus. The bootstrap consensus NJ tree and time tree by using the sequences of Cyt b also showed that three populations separated from each other. Finally, the study concluded considerable morphological, shape and genetic variation exists among three A. testudineus populations. The study predicted the probable chances of speciation among them in future. Therefore, proper conservation steps as well as proper broodstock management and breeding strategies are highly required, to protect our indigenous A. testudineus.