Pentasters

A small number of dinoflagellates contain an internal skeleton. One of the best known species is perhaps Actiniscus pentasterias, in which each cell contains a pair of siliceous five-armed stars surrounding the nucleus. This species was originally described by Ehrenberg.^[1] Although the description is incomplete and without illustrations, Ehrenberg described the skeletal elements but mentioned that the living cell was colorless and non-motile. Ehrenberg subsequently diagrammed the silicified skeletal elements (pentasters) from geological deposits in various parts of the world.^[2] These can be found as microfossils. Pentasters were studied from the Cenozoic South Pacific by Dumitrică http://deepseadrilling.org/21/volume/dsdp21_25.pdf ^[3] Tappan ^[4] gave a survey of dinoflagellates with internal skeletons. This included the first detailed description of the pentasters in Actiniscus pentasterias, based on scanning electron microscopy.

The ultrastructure of Actiniscus pentasterias was investigated.^[5]