Leucodictyon marinum n. gen., n. sp., a plasmodial protist with zoospore formation from the Japanese coast

Abstract

Summary Leucodictyon marinum n. gen., n. sp., deriving from tide pools near the Shimoda Marine Research Center (Japan), could be isolated and cultivated with the pennate diatom Amphiprora spec. as food organism. Like Reticulosphaera japonensis ( Grell 1990 a ) from the same habitat, it is a meroplasmodial protist, consisting of small cell bodies which form a common network of slender reticulopodia. Each cell body is enclosed by a loaf-shaped lorica. Through its aperture a reticulopodial root connects the cell body with the remaining network. If the diatoms become sparse, many cell bodies carry out an unequal binary fission. The smaller daughter cell remains within the lorica. The larger daughter cell transforms into a biflagellate zoospore which leaves the lorica through the aperture. The anterior flagellum of the zoospore is short and propels the cell by gyration, whereas the posterior flagellum is long and “trails” behind. Since plastids are lacking, classification is difficult. An ultrastructural study may clarify the taxonomic position.