Autecology,pigment composition and toxicology of Dictyocha octonaria (Dictyochophyceae,Ochrophyta) from Wellington Harbor,New Zealand

Growth and pigment composition of both the skeleton‐bearing and naked forms and toxicology of the naked form of Dictyocha octonaria were studied here using clonal cultures derived from a single cell from Wellington Harbour. In this study both the naked and skeleton‐bearing forms showed optimum growth between 14 and 18°C. Maximum growth rates of the naked and skeleton‐bearing forms were 1.46 and 0.99 division day^?1, respectively. Growth rates of the naked form at temperatures <18°C were found to be greater than those of the skeleton‐bearing form. The reverse was true at temperatures >22°C. Cells of the naked form died at 24°C while those of the skeleton‐bearing form at 26°C. In this study the naked and skeleton‐bearing forms cultured in identical growth conditions contained almost the same pigments, except zeaxanthin, which made up about 3.2% of the total carotenoid in the skeleton‐bearing form and virtually none in the naked form. Toxicological tests conducted on rotifers indicated that the naked form was not harmful to the test organisms.