Ettliella tetraspora (Chlorophyta, Chlorophyceae): life cycle and taxonomy.

Abstract

The morphology and mode of reproduction in Ettiella tetraspora Hindak 1988, a green coenobial alga described from the Czech Republic and Finland, were studied from the plankton of the water reservoir Formitzspeicher in NE Bavaria, Germany. The morphology of cells and coenobia of the species in this population was in agreement with published data for the species, but its reproduction was not of the Oocystis - type as it has been declared in the relevant literature. The protoplast of mother cells does not divide simultaneously into 4 autospores as in many coccal green algae, but always in two autospores. The first division of the mother cell is perpendicular to the longitudinal axis of the cell and two walled daughter cells arise. Subsequently, the newly formed daughter cells divide again, but this time perpendicular to the new formed cell cross wall. Ultimately, in a new coenobium all four daughter cells are arranged in parallel. Daughter cells remain inside a slightly enlarged mother cell wall (well visible only near the cross wall) and are released by its gelatinisation. Such subsequent production of four autospores from the mother cell represents a special type of multiplication in the green coccal algae known also in some other species [e.g. Tetrastrum komarekii Hindak 1977, Willea irregularis (Wille) Schmidle 1900, Makinoella tosaensis Okada 1949].