Test Morphogenesis in a Giant Antarctic Foraminiferan

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The giant foraminiferan protist, Astrammina rara, is protected by an outer shell (test) of mineral grains tightly bound by a chemically-resistant, biological cement or extracellular matrix. Cursory observations indicate that A. rara's network of branching and anastomosing pseudopodia collects larger particulates from the sediment, secretes the test matrix, and through its coordinated activity, sculpts the test. The large size, ease of handling, and high abundance of A. rara at the Antarctic collection site makes this organism uniquely suited for studying specific aspects of test construction. Because A. rara is a giant single-cell system, general questions regarding the assembly of extracellular matrix components in a cold-adapted organism can be studied without the complications common to metazoan systems. Adaptations in certain basic cellular processes involved in test construction are of particular interest because these processes are inhibited by subzero temperatures in the cells of organisms from temperate climates. Various biotechnological methods will be used to gain information on test construction at the cellular and molecular levels of analysis. Completion of the proposed studies will not only help solve an interesting and longstanding biological question, but will also provide a framework for future molecular studies of the physiology and evolution of this important protistan taxon.