Acronema sippewissettensis gen nov sp nov, microbial mat bicosoecid (Bicosoecales = Bicosoecida)

A heterotrophic mastigote from the flat laminated Microcoleus-dominated int ertidal microbial mat at the Sippewissett salt marsh, Cape God, Massachuset ts, was isolated into monoprotist culture in the same anoxic medium that le d to spirochete and other anaerobic bacterial enrichments. The protist grew vigorously and was transferred indefinitely in oxic marine medium. Videomi croscopy as well as scanning and transmission electron microscopy were used to document its features. The swimming and perching behavior, nutritional mode (bactivory) and morphology including ultrastructure identify it as an aloricate bicosoecid. The presence of heteromorphic acronematic undulipodia , bilateral bipartite tubular mastigonemes, absence of a cytostome, absence of extrusomes, and presence of "Dauerstadien" (duration stages) distinguis h this from other Cafeteriaceae bicosoecids. Cell division involves a close d intranuclear spindle. The unspecialized bicosoecid morphology and behavio r juxtaposed with oomycete-like vesicles and mastigonemes suggest that this protist may be an extant descendant of a common ancestor of bicosoecids an d other stramenopiles (e.g. labyrinthulids, thraustochytrids and oomycetes) . A new genus and species, Acronema sippewissettensis, are proposed.