Distinctly different behavioral responses of a copepod, Temora longicornis, to different strains of toxic dinoflagellates, Alexandrium spp.

摘要

Zooplankton responses to toxic algae are highly variable, even towards taxonomically closely relatedudspecies or different strains of the same species. Here, the individual level feeding behavior of a copepod,udTemora longicornis, was examined which offered 4 similarly sized strains of toxic dinoflagellateudAlexandrium spp. and a non-toxic control strain of the dinoflagellate Protoceratium reticulatum. Theudstrains varied in their cellular toxin concentration and composition and in lytic activity. High-speed videoudobservations revealed four distinctly different strain-specific feeding responses of the copepod during 4 hudincubations: (i) the ‘normal’ feeding behavior, in which the feeding appendages were beating almostudconstantly to produce a feeding current and most (90%) of the captured algae were ingested; (ii) theudbeating activity of the feeding appendages was reduced by ca. 80% during the initial 60 min of exposure,udafter which very few algae were captured and ingested; (iii) capture and ingestion rates remained high,udbut ingested cells were regurgitated; and (iv) the copepod continued beating its appendages andudcaptured cells at a high rate, but after 60 min, most captured cells were rejected. The various preyudaversion responses observed may have very different implications to the prey and their ability to formudblooms: consumed but regurgitated cells are dead, captured but rejected cells survive and may give theudprey a competitive advantage, while reduced feeding activity of the grazer may be equally beneficial toudthe prey and its competitors. These behaviors were not related to lytic activity or overall paralyticudshellfish toxins (PSTs) content and composition and suggest that other cues are responsible for theudresponses.