Morphological and Genetic Identification of Pseudo-nitzschia H. Peragallo, 1900 (Bacillariophyta) from the Sea of Japan

Abstract

A total of 15 Pseudo-nitzschia strains isolated from Russian coastal waters of the Sea of Japan were identified using light and electron microscopy and phylogenetic analysis of ribosomal genes. Pseudo-nitzschia species are known to be potential producers of neurotoxiс domoic acid and cause blooms. Phylogenetic analysis of LSU and ITS1-5,8SrDNA-ITS2 sequences revealed that the examined strains belong to P. calliantha, P. hasleana, P. multistriata, P. pungens var. pungens, and P. delicatissima. P. hasleana is a new record for the Sea of Japan. Some morphological distinctions of the strains of P. calliantha and P. pungens var. pungens from the original descriptions of the species were detected. The ITS1-5,8SrDNA-ITS2 topologies showed that the P. delicatissima clade A is formed from three subclades, including Pacific strains, as well as isolates from Scotland and Spain. The high values of genetic distances between subclades (3.7-5%) and the morphological similarity between strains are indicative of cryptic genetic diversity within the P. delicatissima clade A. Different ITS types, including a possibly recombinant type, occur in the same monoclonal culture of P. multistriata, suggesting the hybridization of the local populations in the studied area.