Intracellular Barite Crystals in Two Xenophyophores, Aschemonella Ramuliformis and Galatheammina Sp. (Protozoa: Rhizopoda) With Comments on the Taxonomy of A. Ramuliformis

Biological precipitation of barite (barium sulphate) is highly unusual (Bowen, 1966, p. 129). This mineral forms statoliths in certain ciliates (Hubert et al. 1975), but the only animals in which it is known to occur in significant quantities are xenophyophores, a group of giant deep-sea protozoans placed in a separate class within the Rhizopoda (Levine et al. 1980). The importance of these previously obscure organisms at abyssal, and bathyal depths in the oceans has lately become increasingly appreciated, mainly through the work of Tendal (1972, 1973, 1975a, b, 1980a, b; Tendal & Lewis, 1978).