Bloom: No
Toxicity: Yes_DSP
Cytologic description : Live cells were 34 mm long and ca. 25 mm wide The chloroplasts in starved cells were reduced to the poles of the cell, while they were larger in well-fed cells  In D. acuminata, the single dinoflagellate nucleus was located in the central–posterior part of the cell. The chloroplasts were arranged in two axial clusters, one in the anterior part of the cell, the other immediately behind the nucleus. Each chloroplast had a terminal pyrenoid, andall pyrenoids congregated in a complex, compound pyrenoid (a posterior chloroplast complex). Thenumber of pyrenoids appeared to be rather high, perhaps 10 per cluster, and long, thin chloroplast branches extended from the pyrenoid into the cell or towards the cell periphery. Some of the branches were seen to merge distally. Thylakoidwere absent in the pyrenoids but elsewhere in the chloroplasts were typically arranged in pairs. The lumen of each thylakoid in this figure was translucent. Details of the chloroplast envelope and the pyrenoids were represented by the anterior pyrenoid complex. Each chloroplast was separated from the cytoplasm or from other chloroplasts by two membranes, but incomplete remains of a third membrane were sometimes visible in the space between the two complete membranes, especially in the area between the individual pyrenoids. In cases where three membranes were visible, the innermost two membranes were situated close together. The terminal position of each pyrenoid was visible. Occasionally two chloroplast branches were seen to extend from the same pyrenoid. Food vacuoles were commonly seen in the sections, thus three food vacuoles were visible. The contents of the vacuoles could not be identified. The internal parts of the peduncle. served in food uptake. The peduncle was large and comprised a band of 100 microtubules lined by vesicles with electron opaque content clearly visible in the transverse sections. The microtubular strand extended through a considerable part of the cell, and the anterior tip of the peduncle  was retracted to a position just beneath the cell exterior. Inthe oblique section, one opaque vesicle extended alongside themicrotubular ribbon.