Coccolith size rules – What controls the size of coccoliths during coccolithogenesis?

TitleCoccolith size rules – What controls the size of coccoliths during coccolithogenesis?
Publication TypeJournal Article
Year of Publication2022
AuthorsSuchéras-Marx B, Viseur S, Walker CE, Beaufort L, Probert I, Bolton C
JournalMarine Micropaleontology
Volume170
Pagination102080
ISSN0377-8398
KeywordsBiometry, coccolith, coccolithophore, life cycle, RCC1216, Size variation
Abstract

Heterococcoliths are calcite platelets produced inside diploid coccolithophore cells and extruded to form a covering on the cell surface called a coccosphere. The size of coccoliths is an important parameter sometimes used to identify species, and it is observed to be influenced in extant species by abiotic parameters (e.g., CO2, light). However, the variable distribution of coccolith sizes occurring within a single coccosphere questions the mechanisms controlling coccolith size. A relationship between cell/coccosphere size and mean coccolith size was previously identified, called the “coccolithophore size rules”. In this study, we query the mechanisms controlling the size of a coccolith during coccolithogenesis. A culture experiment on Gephyrocapsa huxleyi strain RCC1216 shows that coccolithogenesis occurs during the cell growth G1 interphase and newly produced coccoliths get bigger as the cell grows. These observations provide parameters for the development of two numerical models used to simulate the coccolith size distribution within a coccolithophore population. Neither model can accurately reproduce an empirical monoclonal coccolith size distribution, indicating that additional factors influence coccolith size. According to our results, coccolith size is only clearly related to cell size at the time of its formation. We confirm that application of the coccolithophore size rules model should be limited to inferring average cell dimensions from (fossil) coccolith biometry, and that comparisons are valid only in multipopulational studies. The coccolith size rule model – the constraining effect of coccolith production during G1 interphase cell growth on coccolith size – proposed here is applicable only for some placolith-forming species.

URLhttps://www.sciencedirect.com/science/article/pii/S0377839821001213
DOI10.1016/j.marmicro.2021.102080