Identification of the wedge clam Donax trunculus by a simple PCR technique

The wedge clam Donax trunculus is an important bivalve commercial species in Portugal which can be easily mistaken with other three morphologically similar species (Donax semistriatus, Donax vittatus and Donax variegatus) that have a lower market price. This may lead fish sellers to make false claims about the authenticity of their products in order to get higher profits. To overcome this problem it is important to develop analytical techniques that can be used to test the authenticity of the species that is being sold. In this study we present two DNA extraction methodologies and a simple PCR method for the accurate identification of D. trunculus based on the amplification of the nuclear marker 5S rDNA. The PCR amplification results showed that this method is reliable to differentiate D. trunculus and D. variegatus from the remaining Donax species, since fragments of D. trunculus were about 275–300bp while D. variegatus were about ∼450 bp a little lower molecular weight than DNA fragments of the other two species (∼500 bp).