Reticulosphaera socialis n. gen., n. sp., ein plasmodialer und phagotropher Vertreter der heterokonten Algen / Reticulosphaera socialis n. gen., n. sp., a Plasmodial and Phagotrophic Representative of the H eterokont Algae

Abstract

Abstract Reticulosphaera socialis n. gen.. n. sp., a protist deriving from the Caribbean Sea. could be isolated and cultivated. The life cycle consists of a benthic and a pelagic phase. Spherical cells, characteristic of the benthic phase, are united by a common reticulopodium by means of which they capture and digest diatoms (“reticulopodial digestion”). When food gets exhausted, the cellular association (plasmodium) disintegrates into single cells resembling amoebae (“individualization”). After some time, they transform into heliozoan-like cells which float in the seawater. Under unfavorable conditions the spherical cells may encyst. When the diatoms run short and illumination is sufficient, they can survive by means of their plastids. though for a limited time only. Electron microscopical investigations showed that the heliozoan-like cells have not only pseudopodia used as floating projections, but also two flagella. One of the flagella induces an eyespot in a nearby plastid. This situation is characteristic of the so-called heterokont algae (Chrysophyceae, Xanthophyceae). Classification of Reticulosphaera socialis - and a light-microscopically similar species: Chlorarachnion reptans - is discussed.