Inter-Research
Marine Ecology Progress Series

ABSTRACT: The effects of the red-tide dinoflagellate Heterocapsa sp. on Gyrodinium instriatum were studied using laboratory cultures. Growth of G. instriatum was strongly suppressed when cultured together with Heterocapsa sp. Microscopical observations revealed that G. instriatum cells were immobilized by cell contact with Heterocapsa sp. The time necessary for the immobilization of G. instriatum cells decreased with increasing cell densities of Heterocapsa sp., which was related to the increasing chance of contact between the 2 organisms. Immobilized G. instriatum cells became abnormal in shape and finally lysed. H. triquetra had no effect on the motility of G. instriatum. This is the first report of inhibition of phytoplankton growth by cell contact.

KEY WORDS: Killer phytoplankton . Heterocapsa sp. . Cell contact . Immobilization . Growth inhibition . Gyrodinium instriatum

Published in MEPS Vol. 118 (1995) on March 9
Print ISSN: 0171-8630; Online ISSN: 1616-1599. Copyright © Inter-Research, Oldendorf/Luhe, 1995