Taxonomy and distribution of the unarmored dinoflagellates Cochlodinium polykrikoides and C. fulvescens

Abstract

Red tides of the unarmored dinoflagellate Cochlodinium polykrikoides and related Chain-Forming Cochlodinium species have been responsible for the mass mortality of fish in coastal areas of East Asia, and in Central and North America over the past few decades. Since 2000, C. polykrikoides has been reported for the first time from Southeast Asia, India, the Middle East and the Mediterranean, so its distribution has seemingly expanded. Recent molecular phylogenetic works have detected intraspecific populations of C. polykrikoides , which presumably indicates their original distribution area. Reported occurrences of the chain-forming Cochlodinium spp., Cochlodinium fulvescens and C. polykrikoides are summarized with reference to their ribotypes, in order to consider the expansion of their distribution area and recent migration. The ultrastructure of C. polykrikoides was recently analyzed and showed the characteristic features seen in all other dinoflagellates. The apical groove structure of C. fulvescens is also provided in this chapter, for morphological comparison with C. polykrikoides and further characterization of chain-forming Cochlodinium spp. that produce fish-killing red tides.