Molecular characterization of the Marteilia parasite infecting the common edible cockle Cerastoderma edule in the Spanish Mediterranean coast

Marteilia spp. parasites such as M. refringens are notifiable pathogens of commercial bivalves with detrimental effects on shellfish fisheries and aquaculture. Recently a Marteilia parasite has been described infecting the common edible cockle Cerastoderma edule for the first time in Spain, with only one previous report from elsewhere in the world. Molecular characterization was carried out, based on the rDNA intergenic spacer (IGS), the internal transcribed spacer 1 (ITS-1) and the 18S rRNA, of the Marteilia parasite reported infecting the cockle C. edule in the Spanish Mediterranean coast in order to better understand the epidemiology of the pathogen. Partial IGS sequences obtained showed 83% of maximum identity with Marteilia refringens when analyzed by BLAST. Further, 86% was recorded for the partial ITS-1 and 98% for the partial 18S rRNA region studied. Comparison by multiple alignment of ITS-1 sequences, genetic distance matrix of the IGS, and a phylogenetic analysis using the IGS sequence support the existence of a new Marteilia species infecting bivalves in Europe. Furthermore, an IGS PCR–RFLP digestion with the BgL II enzyme is described in order to facilitate discrimination between the cockle Marteilia and M. refringens infecting other bivalves in Europe. ►The molecular characterization of the Marteilia found in cockle was carried out. ►Three regions (18S, ITS-1 and IGS) of the ribosomal DNA cistron were studied. ►Important genetic divergences were observed when comparing with M. refringens. ►Present results show a new Marteilia type “C” that can be detected by digestion. ►Results support the existence of a new Marteilia specie infecting bivalves in Europe.