Toxin and molecular analysis of Gymnodinium catenatum (Dinophyceae) strains from Galicia (NW Spain) and Andalucía (S Spain)

Abstract

Nineteen strains of Gymnodinium catenatum were isolated from one bloom in Andalucía (S Spain) and from different blooms in Galicia (NW Spain). The PSP toxin profiles of 16 of the strains were analyzed, and although the saxitoxin was exclusive to the Galician strains, the corresponding dendogram showed no clustering of the isolates from this location. However, nine out of eleven Andalusian strains were included in the same cluster. In order to compare toxin with molecular analysis, a fragment of the large subunit ribosomal (LSU) RNA gene was partially sequenced for all of the strains and fully sequenced for the five strains that had shown most different growth curves. Since all the strains were identical in the LSU sequenced region, another fragment comprising the internal transcribed spacer 1 (ITS 1), 5.8S rRNA gene and ITS 2, was sequenced and compared among all the strains. Although this region has been used before for the detection of intraspecific variability, it was similar in all our strains. Finally, to detect molecular differences in the strains, a random amplified polymorphic DNA (RAPD) analysis was performed. The corresponding cluster analysis grouped the strains in three clusters: one of them comprised all the Galician strains plus three from Andalucía, another one included eight Andalusian strains, and the last one, more separated from the two previous, was constituted by two Andalucía isolates. Although the results of the toxin and RAPD analysis were different, seven Andalusian strains were clustered together in both dendograms. Since neither the toxin nor the RAPD analysis brought out a clear geographic signal, we can conclude that differences in toxin content and RAPD profile between the isolates of G. catenatum are probably not linked to the location in which the strains were collected.