Effect of the PSP-causing dinoflagellate, Alexandrium sp. on the initial feeding response of Crassostrea gigas
Fisheries and Oceans Canada, Biological Station, St. Andrews, NB E0G 2X0, Canada
2 IFREMER, B.P. 21105, 44311 Nantes cedex 031, France
Accepted: 27 October 1997
The effects of toxic and non-toxic strains of Alexandrium sp. on the initial feeding responses of the Pacific oyster Crassostrea gigas were determined by continuous monitoring of the clearance rate of individual oysters. This was determined fluorometrically by loss of fluorescence of live microalgae introduced as food. Feeding oysters with toxic or non-toxic A. tamarense and toxic A. fundyense resulted in stop/start clearance behaviour. In contrast, control oysters fed a reference microalga, Isochrysis sp., known to support their growth, did not exhibit this behavior. Pacific oysters acclimated to Isochrysis sp., fed mixtures of Alexandrium/Isochrysis, showed further evidence of stop/start clearance. Exposure for periods up to 48 hours with non-toxic A. tamarense did not enhance clearance of either Alexandrium or Isochrysis.
Key words: Crassostrea gigas / feeding physiology / toxic microalgae / dinoflagellate / paralytic shellfish poisoning
© Elsevier, IRD, Inra, Ifremer, Cemagref, CNRS, 1998