AMPHISTEGINA (FORAMINIFERA) BIOCALCIFICATION DURING MULTIPLE FISSION

ABSTRACT

Foraminifera are among the most prolific calcifying protists, yet while adult calcification has been studied extensively, shell formation in juvenile stages remains poorly understood. This study investigates the calcification strategy of the first chamber (proloculus) in Amphistegina during multiple fission. We demonstrate that newly-formed juveniles are housed within a specialized, membrane-enclosed ‘brood chamber’ that shields them from the surrounding milieu. Within this microenvironment, the parent cell provisions offspring with essential calcification substrates: a mineral precursor in the form of magnesium-rich amorphous calcium carbonate (Mg-ACC), an organic matrix, and symbiotic algae. This Mg-ACC is synthesized nocturnally by the parental cell and subsequently released along with the cytoplasm during reproduction. By supplying the mineral precursor, the parent facilitates the rapid and effective construction of prolocular shells, facilitating reproductive success.