CHAMBER FORMATION AND BIOMINERALIZATION IN TEXTULARIA-CANDEIANA DORBIGNY (SARCODINA, TEXTULARIINA)

Light, scanning electron, and transmission electron microscope studies of chamber morphogenesis in laboratory-cultured Textularia candeiana reveal six constructional stages: Stage 1-Collection of particles to form a detritic cover. Stage 2-Development of a chamber lumen and sorting of particles inside the detritic cover. Stage 3-Selection of particles for the new chamber wall. Arrangement of these particles on the construction front, starting on the penultimate chamber of the test and continuing towards the aperture. Simultaneous organic envelopment and organic cementation of each particle. Stage 4-Deposition of biomineralized calcite from the distal to the proximal chamber wall. Development of a pore system by oriented deposition of the biomineralizate, forming cylindrical cavities. Stage 5-Organic lining of these pores. Stage 6-Formation of a thin organic sheet inside the chamber wall, after the foraminifer leaves the detritic cover. Development of a multi-layered inner organic lining during continuous test growth. The construction process from stage 1 to stage 5 is normally completed within 24 hours. Similar observations on other species suggest that these stages can serve as a generalized model of chamber formation in calcite-cemented agglutinated foraminifers.