Elemental composition and ultrafine structure of the skeleton in shell-bearing protists-A case study of phaeodarians and radiolarians.

Cross-sections were prepared by ultramicrotome (UM) and focused ion beam (FIB) system in order to examine the skeletal structure of ecologically and geologically important shell-bearing protists: phaeodarians and radiolarians. The elemental composition of the skeleton was clarified by the energy dispersive X-ray spectroscopy, suggesting that the skeletons of both groups are mainly made of amorphous silica (SiO·nHO) with other minor elements (Na, Mg, Al, Cl, K, Ca and Fe) and that these two groups have similar elemental composition, compared with other siliceous organisms (diatoms and sponges). However, the structural difference among the two groups was confirmed: phaeodarian skeletons are porous, unlike radiolarians with solid skeletons.

Nutritional Intake by Ectoplasmic Nets of Schizochytrium aggregatum (Labyrinthulomycetes, Stramenopiles).

Thraustochytrid cells attach to their food via ectoplasmic nets (ENs). Here, we analyzed the cause and effect relationship between the various forms and functions of ENs of Schizochytrium aggregatum. The ENs spread out over a large area forming a fine network to efficiently search for the experimental food source.

Bothrosome Formation in Schizochytrium aggregatum (Labyrinthulomycetes, Stramenopiles) during Zoospore Settlement.

Labyrinthulomycetes are characterized by the presence of ectoplasmic nets originating from an organelle known as the bothrosome, whose evolutionary origin is unclear. To address this issue, we investigated the developmental process from a zoospore to a vegetative cell in Schizochytrium aggregatum. After disappearance of the flagellum during zoospore settlement, the bothrosome emerged at the anterior-ventral pole of the cells.