Ungeschlechtliche Fortpflanzung durch Querteilung bei der solitären Sand-Ascidie Seriocarpa rhizoides

Abstract

A process of asexual reproduction by transverse constriction, hitherto unknown in solitary ascidians, has been discovered in Seriocarpa rhizoides. Reproductive stages were found among specimens fixed immediately after collecting from graband trawl samples (plateau of Josephine-Bank between Lisbon and Madeira) and among other specimens kept in aquaria for several months. Dividing individuals contract strongly for a period during which internal organs undergo dedifferentiation. New siphons grow near the middle region, and internal structures develop paralleling regenerative processes. The method of asexual reproduction points to the close relationship of solitary and compound species of the family Styelidae, supporting van Name's (1921, 1945) hypothesis that no distinct evolutionary isolation exists between these two groups. Asexual reproduction by transverse division is considered part of an adaptation to life on an isolated sea-mount (biological "sea-mount effect"). © 1972 Biologischen Anstalt Helgoland.