A DESCRIPTION OF THE TESTATE AMEBA OVULINA-PARVA GEN-NOV, SP-NOV FROMCOASTAL MARINE-SEDIMENTS

A testate amoeba with organic test, isolated from sediments in the Fir th of Clyde, Scotland, has been assigned to a new genus as Ovulina par va (Protista: Filosea) based on its unique light microscopic and fine structural morphology. The hyaline to amber test is ovate (similar to 15x11 mu m) with a terminal aperture that is either unadorned or with a shallow collar. Hyaline, long-tapering, pointed, sometimes branched, pseudopodia emerge directly from the aperture or from the periphery o f a thin web of hyaline cytoplasm. The nucleus (similar to 5 mu m) wit h a central nucleolus (similar to 2 mu m) is located at the posterior of the cytoplasm. The fine structure of the test, examined by scanning and transmission electron microscopy, shows it is entirely organic wi th an irregular to granular surface. Scattered elongate pits (similar to 1 mu m long) without perforations are distributed irregularly on th e surface. Ectoplasm is distributed within a fine fibrillar envelope l ining the test. The endoplasm is ovoid and contains anteriorly located vacuoles enclosing densely-staining bodies with chromatin-like filame nts which appear to be bacterial prey in late stages of digestion. Thi s is further corroborated by light microscopic observations that bacte ria are cleared from the surface of the culture dish within the circum ference of the pseudopodia. The mitochondria (0.5-1.0 mu m) have tubul ar cristae and some are located in the vicinity of peroxisomes (simila r to 0.5 mu m) surrounded by a single membrane and with a finely granu lar matrix Minimum doubling time in our cultures was 28.4 h, and the t estate amoeba exhibits remarkable salinity tolerance growing in media ranging from 0 to 35 parts per thousand salinity.