What is new in coccolithophore biology?

Abstract

Knowledge of the biology of coccolithophores has progressed considerably in recent years thanks to culture studies and meticulous observations of coccospheres in wild samples. It has been confirmed that holococcolithophores and other "anomalous" coccolithophores are not autonomous but stages in the life cycle of oceanic heterococcolithophores. The existence of such heteromorphic life cycles linking former "species" has far reaching consequences on the taxonomy and nomenclature of coccolithophores and should foster research on the environmental factors triggering phase changes. The cytological characteristics of coccolithophores are reviewed in detail with special attention to the cell covering, coccolithogenesis and the specificity of appendages in this group. There have been comparatively few recent studies concerning the cytology of oceanic representatives. Important issues such as status of aplastidic groups, mode of synthesis of holococcoliths/nannoliths and details of the flagellar apparatus need to be addressed. Such morphological data will enable a more natural classification of modern coccolithophores in a phylogenetic perspective.