Euryhaline Chrysomonads: Nutrition and Toxigenesis in Prymnesium parvum, with Notes on Isochrysis galbana and Monochrysis lutheri

SYNOPSIS. The nutritional requirements of 3 isolates of Prymnesium parvum (2 Israeli, 1 Scottish) included vitamin B 12 and thiamine. For comparison, 2 other brackish chrysomonads were studied: Monochrysis lutheri isolated by Droop in Scotland and Isochrysis galbana purified by McLaughlin from a culture obtained from the Plymouth laboratory. The isolates of Prymnesium parvum and Isochrysis galbana had a molecular B 12 specificity like Ochromonas malhamensis : no response to Factor B, pseudovitamin B 12 , Factor A or Factor H. M. lutheri , in contrast, responded to pseudovitamin B 12 , Factor H, and Factor A. Thiamine was essential; 1.0 μg.% allowed full growth of P. parvum. The NaCl concentration for good growth was 0.3–5.0%; growth was possible from 6–12%. Dark growth was not achieved. Ammonia, as suggested from its use in suppressing outbreaks of P. parvum , was sharply inhibitory, less so at high concentrations of NaCl or at acid pH. Nitrate, ammonia, arginine, asparagine, methionine, histidine, alanine, glycine, serine, proline, leucine, isoleucine, tyrosine, aspartic and glutamic acids, acetylurea, and creatine served as nitrogen sources in both acid and alkaline media. The phosphate requirement of P. parvum and M. lutheri and Isochrysis galbana was satisfied by inorganic phosphate, commercial glycerophosphate, yeast adenylic acid, cytidylic acid, monoethyl phosphate, and riboflavin monophosphate. Laboratory cultures in defined media of the isolates of P. parvum were toxigenic to Lebistes and Gambusia. Culture fluids from alkaline media were more toxic than those from acid media, as previously noted in Israel. Culture media suitable for production of large quantities of these organisms were developed.