SCANNING ELECTRON-MICROSCOPE STUDY OF DINOSPORES OF AMYLOODINIUM CF OCELLATUM, A PATHOGENIC DINOFLAGELLATE PARASITE OF MARINE FISH, AND COMMENTS ON ITS RELATIONSHIP TO THE PERIDINIALES

Trophonts of a parasitic dinoflagellate were obtained from the gills o f feral and cultured red drum Sciaenops ocellatus and aquarium-housed sebae clownfish Amphiprion clarkii, imperator Pomacanthus imperator, m andarin goby Pterosynchiropus splendidus and flame angelfish Centropyg e loriculus. After incubation of tomonts, dinospores were studied by s canning electron microscopy. Dinospores have a plate pattern and tabul ation of Po, cp, x, 4', 1a, 7'', 6 to 8?c, ?s, 5''', 2'''', which are similar to that of the free-living Peridiniales. The parasite is tenta tively identified as Amyloodinium cf. ocellatum. Most descriptions of parasitic dinoflagellates rely only on the morphology of the trophont. However, despite the fact that some past studies have questioned the validity of using dinospores in making taxonomic classifications becau se of their plastic and unstable morphological characteristics, dinosp ore characterization is critical. Traditionally, dinospores of parasit ic dinoflagellates have been described as unarmored (naked) and have b een considered to have gymnodinioid, gyrodinioid or cochlodinioid form s. Ultrastructural fixation techniques used for A. cf. ocellatum revea led the presence of thin plates arranged in Kofoidian series. Such pla tes could be more prevalent in other dinoflagellate species than has b een previously indicated, and existing taxonomic-classification scheme s may need to be emended. Dinospores of other parasitic dinoflagellate s should be reevaluated for the presence of similar diagnostic charact eristics.