The marine dinoflagellate genus Dinophysis (Dinophyceae): photosynthetic, neritic and non-photosynthetic, oceanic species
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Some thirty Dinophysis species from Australian tropical and temperate, coastal and oceanic waters were examined by fluorescence and scanning electron microscopy, and eight selected species were also studied by transmission electron microscopy. The dinoflagellate genus Dinophysis, as currently circumscribed, includes forms with elevated epitheca and straight horizontal girdle lists (species previously allocated to Phalacroma) and forms with reduced epitheca and the girdle lists curved up anteriorly from the cell body (Dinophysis sensu stricto). Members of the first species-group are predominantly heterotrophic, oceanic dinoflagellates. An exception is Phalacroma rapa, which is a sparsely pigmented, tropical, neritic species with unusual, small chloroplasts (different from those of typical photosynthetic forms such as Dinophysis acuminata and D. fortii). Members of the second species-group are predominantly photosynthetic, neritic dinoflagellates. Exceptions are Dinophysis hastata and D. schuettii, which are heterotrophic, oceanic forms without chloroplasts but with large food vacuoles, which sometimes contain identifiable food particles such as bacteria, virus-like particles and ingested algal cells. Physiological and ecological arguments are thus provided in partial support of the original generic distinction between Dinophysis and Phalacroma. Current ideas on phylogenetic relationships within the dinophysoid dinoflagellates are refined with emphasis on the acquisition of symbionts and chloroplasts.