Morphology, phylogeny, and toxicity of Atama complex (Dinophyceae) from the Chukchi Sea

Abstract

The “Atama complex”, which consists of Alexandrium tamarense, A. fundyense, and A. catenella, is one of the most important groups within the dinoflagellate genus Alexandrium. Information of the biogeography of the Atama complex is limited in the Arctic Ocean. In the present study, we established 55 strains of the Atama complex by incubating ellipsoidal cysts collected from the Chukchi Sea. The vegetative cells are characterized by a prominent ventral pore, thereby fitting the description of A. tamarense morphotype. Large subunit (LSU) and/or internal transcribed spacer (ITS) region sequences of these strains were examined. Both sequences showed intragenomic polymorphism. The 708 bp of the LSU sequences from the strains differed from each other at 0–44 sites (0.0–6.2 %), and the ITS region sequences differed from one another at 0–28 sites (0.0–5.4 %). Phylogenetic analysis revealed that the Chukchi Sea strains were nested within Atama complex (Group I). Assessment of paralytic shellfish poisoning toxin production by four Chukchi Sea strains using high-performance liquid chromatography showed that total toxin per cell ranged from 9 to 41 fmol cell−1. The toxin profile of the four strains from the Chukchi Sea is conserved, with the major toxins being N-sulfocarbamoyl toxin (C2), saxitoxin, and gonyautoxin-4. Our results support that dispersal of the Atama complex (Group I) from the Bering Sea to the Chukchi Sea might have occurred.