RETICULOSPHAERA-JAPONENSIS N-SP (HETEROKONTOPHYTA) FROM TIDE POOLS OF THE JAPANESE COAST

In addition to the type species, Reticulosphaera socialis (GRELL 1989), a new species of the same genus, Reticulosphaera japonensis n. sp., deriving from tide pools near the Shimoda Marine Research Center (Japan), could be isolated and cultivated. Feeding on diatoms, Reticulosphaera japonensis does not form "circular areas" as the type species, but produces small clusters corresponding to little meroplasmodia. Their spherical cell bodies carry out binary fission and may also change into "transitional cells" which leave the cluster and transform into the pelagic "heliozoan-like cells". The latter have much longer pseudopodia, serving as floating projections, than the "H-cells" of Reticulosphaera socialis. They penetrate a layer surrounding the cell body. All mentioned stages can be found also when the diatoms become sparse and the cells change from heterotrophy to autotrophy. Peculiar stages, not to be seen in Reticulosphaera socialis, suggest syngamy and meiosis but need to be investigated more thoroughly before this conclusion can be drawn.