Cell Division in Gonyaulax catenella, A Marine Catenate Dinoflagellate*

Abstract

SYNOPSIS Mitosis and cytokinesis are described and illustrated for the first time in the mesokaryotic, catenate dinoflagellate Gonyaulax catenella. A structure similar to the central body of G. tamarensis and G. monilata is shown by light and electron microscopy to be situated intranuclearly near the arms of the U‐shaped interphase nucleus, and is suggested to function in the segregation of daughter chromosomes. This structure has the fine structure of a nucleolus, and it is suggested that the term central body be replaced by persistent nucleolus (= endosome). The time required for the completion of mitosis is 4–6 hr, while cytokinesis requires at least 2 hr. Cytokinesis begins during the mitotic cycle, and the plane of fission is perpendicular to the mitotic plane of division. Parental fission moieties are retained and shared by the daughter cells while either a new antero‐sinistral moiety or a posterodextral moiety is synthesized by the dividing cell.

A Quantitative Assessment of the Role of the Parasite Amoebophrya in the Termination of Alexandrium fundyense Blooms within a Small Coastal Embayment

“…Examples of mating A. fundyense gamete pairs of A. fundyense cells were distinguished from dividing cells by their angle of attachment. Whereas dividing A. fundyense are always oriented relative to one another with their cingular grooves parallel [30], the cingular grooves of fusing gametes are often oriented obliquely, allowing them to be distinguished after fixation and staining.…”

Life cycle studies of the red tide dinoflagellate species complex Alexandrium tamarense

“…The net effect of these behaviors is that -in a growing population of A. t. Group I -G2+M cells are only abundant during early morning (Tomas 1974;. In contrast, A. t. Group I planozygotes (also 2c in DNA content) remain in the plankton for approximately one week before transforming to hypnozygote cysts (Anderson, Chisholm et al 1983;Anderson and Lindquist 1985 …”