MORPHOSPECIES VS GENOSPECIES IN TOXIC MARINE DINOFLAGELLATES - AN ANALYSIS OF GUANIDINIUM-CATENATUM GYRODINIUM-IMPUDICUM AND ALEXANDRIUM-MINUTUM ALEXANDRIUM-LUSITANICUM USING ANTIBODIES, LECTINS, AND GENE-SEQUENCES

Morphological features are the predominant criteria used to define spe cies of marine dinoflagellates. Taxonomic problems with some toxic gro ups has bed to the implementation of molecular taxonomy techniques and development of a genospecies concept. As a result, the relationships between ''morphospecies'' and ''genospecies'' has been questioned. In this study the genetic differentiation between two sets of closely rel ated morphospecies, Gymnodinium catenatum Graham/Gyrodinium impudicum Fraga and Alexandrium minutum Halim/Alexandrium lusitanicum Balech, we re analyzed. The extent of morphological differentiation existing with in these two groups is of the same order of magnitude. Analysis of cel l surface antigens detected by preadsorbed serum, cell surface glycan moieties detected by lectins and sequencing of the D9 and D10 domains of the Large-subunit ribosomal RNA gene, showed that the extent of gen etic differentiation existing between the dinoflagellates Gymnodinium catenatum/Gyrodinium impudicum is substantial. Therefore, bath morphol ogical and genetic criteria resolve these organisms as two distinct en tities. In contrast, Alexandrium minutum/Alexandrium lusitanicum were indistinguishable using the some suite of molecular markers. The findi ngs demonstrated that classifications based on morphological criteria may be incongruous. On a practical level, molecular taxonomy provides useful tools to distinguish between morphologically similar microalgal species and furthermore can prevent misidentification of species such as Gymnodinium catenatum/Gyrodinium impudicum, a frequent occurrence when samples are fixed with Lugol's or formaldehyde solution.