Population structure of a deep-water squaloid shark, the Portuguese dogfish (Centroscymnus coelolepis)

The genetic population structure of the deep-water squaloid Centroscymnus coelolepis (the Portuguese dogfish) in the eastern Atlantic was investigated using eight polymorphic nuclear microsatellite markers and a 496-bp fragment of the mitochondrial DNA control region (mtDNA CR). Samples (20-50 individuals per location) were collected off Ireland, Portugal, Madeira, Mauritania, South Africa, and the Azores (Mid-Atlantic Ridge). High levels of genetic diversity were found at the nuclear microsatellite loci (mean A = 17.3; overall H-o = 0.77), although there was low diversity at the mtDNA CR (h = 0.65, pi = 0 0.0018). Genetic diversity for the Portuguese dogfish was homogeneously distributed among sampling locations, resulting in low and non-significant indices of genetic differentiation (e.g. F-ST -0013 to 0.0096, Phi(ST) = -0.017 to 0.033; p > 0.5), consistent with the absence of population structure within the area sampled. The results indicate that C. coelolepis has a high dispersal potential within the eastern Atlantic, and its apparent spatial segregation by size and maturity stage suggest large-scale migration associated with the reproductive cycle.