Mitochondrial DNA haplotype diversity and origin of captive sand tiger sharks (Carcharias taurus)

Abstract

The sand tiger shark (Carcharias taurus) is listed as globally vulnerable by the International Union for Conservation of Nature (IUCN) with geographically isolated and separated global populations with little or no gene flow between them. Captive-breeding of these sharks in aquaria would reduce the need to populate displays with wild-caught individuals; however, sand tigers are notoriously difficult to breed in captivity. In this study we analysed 520bp of the mitochondrial D-loop to assess the haplotype diversity of 19 captive sand tiger sharks from aquaria in the UK and US. Genetic material was sampled in a non-invasive fashion through DNA extracted from shed teeth. Data obtained were compared to known, geographically mapped wild haplotypes to establish whether individuals from different global populations are being housed together. Results identified the haplotype of a minimum of 10 of the 19 sharks, detecting four different haplotypes, and identifying a previously undescribed haplotype (haplotype K). A major genetic subdivision between the haplotypes of the North West Atlantic and those of other global populations has been previously shown from population genetic analyses. Our results indicate that captive sharks can be from either side of this subdivision and occasionally these can be co-housed in the same aquarium. Since sharks with highly divergent genetic ancestry are being kept together, these findings have implications for conservation efforts regarding the individual needs of sand tiger shark populations and for captive-breeding program success rates.