On the symbiosis betweenAmphidinium klebsii[Dinophyceae] andAmphiscolops langerhansi[Turbellaria: Acoela]

Abstract

INTRODUCTIONAlgal-invertebrate symbiosis is common among species of acoelus Turbellaria in both marine and freshwater environments (Droop, 1963; Buchner, 1965; McLaughlin & Zahl, 1966). Associations involving these organisms exhibit broad variations in the amount of integration achieved through the reciprocal relations of hosts and symbionts. In the symbiosis involvingConvoluta roscqffensisGraff, the maximum degree of intimacy is achieved, and the host appears totally dependent on its symbiont for its nutritional requirements (Keeble & Gamble, 1907; Keeble, 1910). This type of closed symbiosis is unknown in other invertebrate phyla and may even be unique among turbellarians. Similarly, the association betweenAmphiscolops langerhansi(Graff) and a unicellular alga is a typical example of the more common, open or facultative symbiosis. Both species (with their algal partners) are potentially useful as investigative tools in the study of cellular interaction in algal-invertebrate symbiosis, and may provide the basis for understanding the broader aspects of cellular integration in metazoan tissues. Recent studies ofC. roscqffensisprovide a basis for understanding the biology of the symbiosis which it sustains (Parke & Manton, 1967; Provasoli, Yamasu & Manton, 1968; Provasoli, Yamasu & Mabuchi, 1969). The present communication is intended to provide similar information on the association found inA. langerhansi.