Combination coccospheres from the Eastern Adriatic coast: New, verified and possible life-cycle associations

Coccolithophore life cycles involve the alternation between morphologically distinct life-cycle phases. This often leads to taxonomic issues where the life-cycle phases of the same species are described as distinct taxa. This issue can be resolved by the observation of combination coccospheres, i.e. cells bearing the coccoliths of both life-cycle phases. This study presents new observations on combination coccospheres from the highly diverse and ecologically important coccolithophore order Syracosphaerales and the genus Alisphaera. New life-cycle associations are revealed between Syracosphaera hirsuta and Corisphaera strigilis, and between Alisphaera unicornis and a nannolith-producing Polycrater galapagensis. The life-cycle association of Syracosphaera marginiporata - Anthosphaera sp. type B is verified. A possible association between Rhabdosphaera xiphos and an unidentified holococcolith-bearing morphotype is proposed and needs to be verified in future investigations. The appropriate taxonomic revisions are conducted following the taxonomic principle of priority and recommended practices for naming the coccolithophore life-cycle phases.