08 Nov 2023
 | 08 Nov 2023
Status: this preprint is open for discussion.

The calcitic test growth rate of Spirillina vivipara (Foraminifera)

Yukiko Nagai, Katsuyuki Uematsu, Briony Mamo, and Takashi Toyofuku

Abstract. Foraminiferal groups encompass vastly differing morphologies, ecological preferences and elemental/ isotopic test compositions. For some of these groups, the calcification mechanism is completely unknown, but is likely differing from that of well-studied groups. This study aimed to understand the test growth and calcification rate of Spirillina vivipara Ehrenberg, 1843 (Order Spirillinida), and to compare them to other foraminifera species. Spirillinids have a closely coiled spiral chamber like a tube, yet their calcitic microstructure is unique amongst foraminifera. Calcification observations in S. vivipara facilitate the estimation of carbonate precipitation rates during active test elongation, which are revealed to be independent of the individual’s size. We found that S. vivipara grows its test in response to food availability, suggesting that calcification directly corresponds to cell growth. Timelapse observations of S. vivipara indicate continuous growth, suggesting active growth phases and interspersed rest periods, hinting at potential biological rhythms in the growth and calcification process. We also implemented a 24-hour observation period using Calcein staining, showing calcite precipitation rates of 8.08 µm/hour in S. vivipara, which correspond to approximately 364 nmol/cm2/min i.e. 36.4mg/cm2/min. These rates are higher than those published for other foraminifera and those in most inorganic precipitation experiments. Such high rates in spirillinid foraminifera may explain their distinctive morphology, elemental composition, unusual reproduction and ecological distribution.

Yukiko Nagai et al.

Status: open (until 24 Dec 2023)

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Yukiko Nagai et al.


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Short summary
This research highlights Spirillina vivipara's calcification strategy, highlighting variability in foraminiferal test formation. By examining its rapid growth and high calcification rate, we explain ecological strategies correlating with its broad coastal distribution. These insights amplify our understanding of foraminiferal ecology and underscore their impact on marine carbon cycling and paleoclimate studies, advocating for a species-specific approach in future research.