The molecular phylogeny of oysters based on a satellite DNA related to transposons.

We have analysed a centromeric satellite DNA family that is conserved in several commercial and non-commercial oyster species (Ostrea edulis, O. stentina, Crassostrea angulata, C. gigas, C. gasar, C. ariakensis, C. virginica and C. sikamea). This satellite DNA family is composed of AT-rich repeat sequences of 166+/-2 bp and presents a 9-bp motif similar to the mammalian CENP-B box. The homology of oyster HindIII satellite DNA with satellite DNAs from other bivalves and its relation to a part of a mobile element suggest the existence of an ancient transposable element as a generating unit of satellite DNA in bivalve molluscs. Taking advantage of its degree of conservation in oyster species, we have used this element as a taxonomic marker. This marker clearly supports a high degree of differentiation between O. edulis and O. stentina, and, conversely, upholds the contention that C. gigas and C. angulata are the same species. Finally, we have used HindIII satellite DNA as a phylogenetic marker between these species, revealing two clades, one formed by Asiatic species (C. angulata, C. gigas and C. ariakensis) and another by the European, American and African species (O. edulis, C. virginica and C. gasar, respectively).