The in vivo and in vitro assembly of cell walls in the marine coccolithophorid, Hymenomonas carterae

Abstract

Hvmenomonas carterae is a member of an ancient group of organisms, the coccolithophorids, so named because of their production of calcareous scales called coccoliths. The coccolithophorids have external appendages, flagella, and a haptonema; the haptonema is a bulbous structure found between the two flagella and may serve as an attachment organelle and aid in controlling movement (Manton, 1968). The coccolithophorids' habitat is predominantly marine with samples taken from tropic, temperate, and arctic seas (Pautard, 1970) where they help to make up a substantial portion of the plankton; one fresh water form has been reported (Manton and Peterfi, 1969). They also have made significant contributions to the fossil record (Pautard, 1970). Hvmenomonas has been referred to in the literature by the genus names Crlcosphaera and Svracosphaera (Paasche, 1968); for my work, I will use Hvmenomonas for the genus name following the recommendations of Manton and Peterfi (1969). These phytoflagellates are classified by the International Committee for Botanical Nomenclature as belonging in the order Coccolithophorales, in the class Haptophyceae, and in the phylum Chrysophyta and by the International Committee for Zoological Nomenclature as belonging in the order Coccolithophorida, in the class Mastigophora, and in the phylum Protozoa (Pautard, 1970). It is not the intention of this report to enter into this controversy. Reviews of coccolithophorids and Hvmenomonas can be found in Paasche (1968), Pautard (1970), and Williams (1972). 4 The life cycle of Hvmenomonas and the other coccolithophorids has been investigated by several authors (