New observations on the heterotrophic protist genus Thaumatomastix (Thaumatomastigaceae, Protista, incertae sedis), with particular emphasis on material from the Baltic Sea

Thaumatomastix (Thaumatomastigaceae, Protista incertae sedis) is a genus of swimming or gliding heterotrophic protists sporadically reported from both marine and freshwater habitats. The cell carries two flagella, one of which is covered by scales, while the other is naked. Both flagellar scales and body scales are produced in vesicles located in close proximity to the outer membranes of the tubulocristate mitochondria. Scales are silicified. In addition to spineless, oval or triangular body scales, in most cases formed by the partial fusion of two almost equally sized plates, some species also possess species-specific spine scales. The genus at present comprises seven species. Six of these are found in samples from the brackish Baltic Sea. However, only T. salina (syn. Chrysosphaerella salina) has been frequently observed in electron microscopical whole mounts. Three new species are described: Thaumatomastix spinosa sp. nov., Thaumatomastix dybsoeana sp. nov. and Thaumatomastix formosa sp. nov.