Growth characteristics and phylogenetic analysis of the marine dinoflagellate Dinophysis infundibulus (Dinophyceae)

Abstract

We report the successful growth of the toxic dinoflagellate Dinophysis infundibulus under laboratory conditions, when fed the marine ciliate Myrionecta rubra grown with the cryptophyte Teleaulax amphioxeia; this study follows previous studies on D. acuminata, D. caudata, and D. fortii, showing the mixotrophy. We succeeded in maintaining several clonal strains of D. infundibulus for a relatively long period of time (> 8 mol. Growth rates in D. infundibulus ranged from 0.40 to 0.94 divisions d -1 , reaching a maximum concentration of 1.2 to 2.3 x 10 3 cells ml -1 . The rate was 0.36 divisions d -1 when apparently fully expanded cells, resulting from the active ingestion of Myrionecta rubra, were cultivated without the ciliate prey. In contrast, the culture of D. infundibulus was not established in the absence of the ciliate or when provided only with the cryptophyte T. amphioxeia, suggesting that D. infundibulus cannot directly use T. amphioxeia as prey. We also determined the sequences of nuclear small subunit (SSU) rRNA, 5.8S rRNA with internal transcribed spacers (ITS1 and ITS2), and large subunit (LSU) rRNA regions in D. infundibulus. Phylogenetic relationships revealed that they are non-identical with regard to any of the DNA sequence data of Dinophysis deposited in GenBank, and are distinguishable from other Dinophysis species for species identification.