Harmful effects of the toxic dinoflagellate Alexandrium tamarense on the tintinnids Favella taraikaensis and Eutintinnus sp.

Abstract

The effects of the exposure of two tintinnids (Favella taraikaensis and Eutintinnus sp.) to the toxic dinoflagellate Alexandrium tamarense were studied, using the non-toxic dinoflagellate Scrippsiella trochoidea as a control. The tintinnid F. taraikaensis showed backward swimming and cellular lysis after a few minutes in the presence of the toxic dinoflagellate A. tamarense in high concentration (280–700 cells ml-1). At low concentrations of A. tamarense (30–120 cells ml-1) no swimming alterations were observed, but cellular lysis occurred after 48 hours. No changes in the swimming patterns were observed when Eutintinnus sp. was exposed to either toxic dinoflagellates or cell-free filtrate, or when F. taraikaensis was exposed to cell-free filtrate. However, both tintinnids suffered cellular lysis after 48 hours of exposure. Favella taraikaensis and Eutintinnus sp. remained healthy after preying on the non-toxic S. trochoidea for 48 hours. In selectivity experiments, F. taraikaensis avoided cells of the toxic dinoflagellates during the dark phase. Our results suggest that tintinnids could play a regulatory role when the toxic blooms are initiating and the toxic cell concentrations remain still low in the northern Patagonian gulfs of Argentina. Since tintinnids are affected by substances released by A. tamarense, predation on dinoflagellates would not occur during the peak of the bloom.

Effects of microalgal exudates and intact cells on subtropical marine zooplankton

“…The effects of Alexandrium exudates on the tintinnid ciliate F. ehrenbergii were previously studied by Hansen (Hansen, 1989), Hansen et al (Hansen et al, 1992) and Fulco (Fulco, 2007) (Table II), who observed a recurring behavioral response: reversal of ciliary movement and continuous swimming backwards with subsequent death. Using the same experimental design, our experiments indicated a reduction in survival after exposure to exudates, with no apparent change in swimming behavior Table I. apart from progressive lethargy.…”

Allelopathic effects of Alexandrium tamarense on other algae: evidence from mixed growth experiments

“…Resale or republication not permitted without written consent of the publisher 1992, Fulco 2007). Turner et al (1998) compiled data on the effects of Alexandrium spp.…”

“…Among the initial sublethal effects on tintinnids are alterations of swimming speed and pattern, including backwards swimming (Hansen 1989, Hansen et al 1992, Fulco 2007. After a few minutes of exposure, cells tend to swell and subsequently lyse.…”

Preliminary Characterization of Extracellular Allelochemicals of the Toxic Marine Dinoflagellate Alexandrium tamarense Using a Rhodomonas salina Bioassay

“…For most of these compounds both the chemical structure and toxicity are well known, mainly because they are toxic to mammals and are therefore of concern to human health [ 7 ]. These compounds have been regarded as putative “defensive compounds” because of their high potency in mammalian systems, and they are also suspected to be allelopathic agents responsible for the deleterious effects on metazoan and protistan grazers and algal competitors [ 8 – 11 ]. Whereas the defensive role of the known phycotoxins may remain valid at least in some cases involving metazoan grazers [ 12 ], with respect to protistan targets, it is now quite clear that neither PSP toxins nor spirolides are involved in the observed negative effects [ 13 , 14 ].…”