COCCOLITH FUNCTION AND MORPHOGENESIS: INSIGHTS FROM APPENDAGE-BEARING COCCOLITHOPHORES OF THE FAMILY SYRACOSPHAERACEAE (HAPTOPHYTA)(1)

J Phycol. 2009 Feb;45(1):213-26. doi: 10.1111/j.1529-8817.2008.00643.x.

Abstract

The morphology of three remarkable genera of coccolithophores, Ophiaster, Michaelsarsia, and Calciopappus, is reviewed based on new images using field emission scanning electron microscopy. Each of these genera characteristically forms coccospheres with long appendages formed of highly modified coccoliths, which radiate from either the circum-flagellar pole of the coccosphere (Calciopappus and Michaelsarsia) or the antapical pole (Ophiaster). For each genus, it is shown that the appendage coccoliths can also occur in an alternative orientation appressed to the main coccosphere. It is hypothesized that the appendage coccoliths are initially deployed in the appressed orientation and that extension of the appendages is a dynamic response to environmental stress. The observations suggest that coccoliths are more sophisticatedly adapted to specific functions than has been assumed and that the cytoskeleton plays more active roles in coccolith morphogenesis and deployment than has previously been inferred.

Keywords: biomineralization; coccolithophore; cytoskeleton; functional morphology; haptophyte.