Molecular characterization of the bivalves Mya arenaria, Mya truncata and Hiatella arctica.

Abstract

Well-preserved bivalve adult forms are generally easily recognizable, but planktonic or damaged samples (crushed organisms in sediments or digested bivalves in predator guts) are far more difficult to identify. 3,18 Molecular approaches may overcome some of these problems. In this paper, we report new PCR-based tests for the identification of three bivalve species within the Myoidae order: Mya arenaria, Mya truncata, and Hiatella arctica based on the internal transcribed spacer (ITS-1) ribosomal DNA region located between the 18S and 5.8S ribosomal RNA genes. Marine bivalves were collected between 1998 and 2000 on the East and West coasts of Scotland, and identified by morphology. Individuals from the following species, which are taxonomically close and commonly found on the coasts of UK, were used in this study: Cerastoderma edule (Linnaeus, 1758), Dosinia exoleta (Linnaeus, 1758), Hiatella arctica (Linnaeus, 1767), Mya arenaria Linnaeus, 1758, Mya truncata Linnaeus, 1758, Mytilus edulis (Linnaeus, 1758), and Venerupis senegalensis (Gmelin, 1791). DNA was extracted from whole Hiatella arctica specimens, whereas for bigger bivalves, such as the Mya species, Cerastoderma edule, Dosinia exoleta, and Venerupis senegalensis, we have used only some parts of the animal (foot or gills). Tissues were digested and DNA was extracted by using a DNeasy Tissue kit (QIAGEN Ltd, Crawley, UK) using the protocol recommended by the manufacturer. Purified DNA samples were stored at ‐ 20°C until needed. A PCR reaction (using previously published ITS2 and ITS5 primers 20 ) was performed on different bivalve species. Unfortunately, bands of 550 bp were amplified from DNA extracted for all the species tested in this study even when the Tm was raised to 56°C instead of 48°C, as recommended 20 (data not shown) and, therefore, could not be used to specifically identify Mya species according to the size of the amplified DNA. Since only a few sequences have been published for these organisms and none are so far in the GenBank for Mya species, we sequenced amplified products from two different Mya species and representatives of Hiatella arctica. DNA fragments were excised from ethidium bromidestained agarose gels using the QIAquick gel extraction kit (QIAGEN Ltd, Crawley, UK) and were sequenced on an ABI 310 DNA sequencer from Applied Biosystems (Warrington, UK) using the Big Dye Terminator kit. Sequences were aligned using the MultiAlin software. 19 Sequences can be retrieved on