PSAMMOPHAGA SAPELA N. SP., A NEW MONOTHALAMOUS FORAMINIFERAN FROM COASTAL GEORGIA, U.S.A.: FINE STRUCTURE, GAMETOGENESIS, AND PHYLOGENETIC PLACEMENT

Abstract

We describe a new monothalamous species, Psammophaga sapela , collected from salt marshes and mudflats along the coast of Georgia, U.S.A. Partial small subunit ribosomal DNA (SSU rDNA) phylogenetic analyses assign this species to Clade E, one of a series of clades of monothalamous foraminifera. Psammophaga sapela joins three previously described species in this genus: P. simplora Arnold, the type species, P. magnetica Pawlowski and Majewski, and the reassigned Allogromia crystallifera Dahlgren. This new species is of moderate size (≤500 μm in length), is generally pyriform in shape, and has a single, flexible aperture, which may occur at the end of a very short neck. The flexible test is composed of a relatively thick (10–15 μm), smooth, outer agglutinated layer of fine clay particles arranged loosely parallel to the plasma membrane of the cell body. The agglutinated layer is underlain by a moderately thick (2–5 μm), inner organic lining (IOL), which is in direct contact with the cell membrane. The IOL contains numerous electron-dense particles with elongated fine fibers similar to other previously reported Clade E taxa. Small vesicles lie just beneath the cell membrane and merge with the plasma membrane to release test construction materials at the base of the IOL. This species is gametogamous, where gamonts release biflagellated gametes either through the aperture or within membrane-bound packets that open following release. Budding was also observed. True to its generic name Psammophaga (sand-eating), this taxon avidly ingests and maintains sediment grains of orthoclase, pyrrhotite, basaluminite, pseudobrookite, anatase, and ilmenite, the latter rendering it magnetic.