Two new species of Isochrysis with remarks on the genus Ruttnera

Two marine strains of Chrysophyceae have been studied with the aid of light and electron microscopy. The benthic stages show definite similarities with two marine Gloeochrysis spp. (G. maritima and G. litoralis) described by Anand (1937), but the swarmers do not agree with the definition of this genus. The reason why they also cannot be assigned to the genus Ruttnera is discussed and their inclusion within the Isochrysidales is justified by the observation of haptophycean scales on the motile cells. The names Isochrysis maritima sp. nov. and Isochrysis litoralis sp. nov. are proposed in view of the fact that these strains might prove to be the species observed by Anand.