Light and electron microscope observations of the type species of syracosphaera, s. Pulchra (prymnesiophyceae)

Abstract

Syracosphaera pulchra, the type species of the genus was isolated into unialgal culture and studied with both the light and electron microscope. A conspicuous coiling haptonema is present containing seven microtubules in the shaft and eight in the basal region; features shared with many taxa in the order Prymnesiales. The proximal and distal coccoliths differ in shape but resemble each other structurally: the outer elements alternate to make the rim. The proximal coccoliths possess an organic base-plate scale which is absent in the distal coccoliths. The uncalcified organic scales are ornamented by a radial, more or less concentric, fibrillar pattern and are arranged in several layers between the proximal coccoliths and the plasmalemma. The ultrastructure of the cell is typical of prymnesiophycean algae. The flagellar apparatus is characterized by the absence of secondary microtubular bundles which are usually well developed in other coccolithophorids with two microtubular roots. This feature is also rather similar to that found in members of the Prymnesiales. This investigation has indicated that S. pulchra has, in some respects, a closer affinity with members of the Prymnesiales than with the coccolithophorids. © 1988 Taylor & Francis Group, LLC.