Syracosphaera halldalii and Calyptrolithina divergens var. tuberosa life-cycle association and relevant taxonomic remarks

Abstract

ABSTRACT: Watersampleswerecollectedforcoccolithophoreanalysisatcoastalenvironments,inAugust2002,from7stationsintheGulf of Kastro (Andros Island, middle Aegean Sea, Eastern Mediterranean). The studies on coccolithophore regional dynamics in themiddle Aegean Sea coastal environments have revealed a unique heterococcolith–holococcolith combination coccosphere indicating alife-cycle association of the taxa Syracosphaera halldalii in Gaarder and Hasle 1971 ex Jordan and Green 1994 and Calyptrolithinadivergens var. tuberosa (Heimdal 1980) Jordan et al. 1993. Consequently their systematic taxonomy is emended and the name Syracosphaera halldalii is considered as the appropriate one for the well-established association. INTRODUCTION Coccolithophores form a major component of the marinenannoplankton and are one of the main open ocean primary pro-ducers, which at least at some points in their life cycle, produceand bear minute calcium carbonate plates called coccoliths.Two structurally different types of coccoliths, heterococcolithsand holococcoliths, formed by different types of biomineral-ization, are recognizable (Young et al. 1999). Several cocco-lithophores have been proven from culture studies to havecomplex life-cycles involving alternate production of holo- andheterococcoliths in the haploid and diploid phases (Houdan etal. 2004). Rare observations from natural populations of combi-nation coccospheres have been interpreted as representing themoment of life-cycle transition, greatly extending the range ofdocumented cases of such life-cycles (e.g. Lecal-Schlauder1961; Kleijne 1991; Cros et al. 2000; Cortes 2000; Geisen et al.2002; Cros and Fortuno 2002; Young et al. 2003). Nonethelessfor the vast majority of extant coccolithophores the life-cycle isunknown and so there is an urgent need for more observations(Jordan et al. 2004).