A novel approach to identifying PST tolerant copepods: An individual ingestion assay

• Published in: Harmful algae 2011-09, Vol.10 (6), p.804-810
• Main Authors: Senft, Christina, Avery, David E., Dam, Hans G.
• Format: Article
• Language: English
• Subjects: Acartia; Acartia hudsonica; Alexandrium; Alexandrium fundyense; Alexandrium tamarense; Algae; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; Copepod; diet; fecundity; females; Fundamental and applied biological sciences. Psychology; Individual; ingestion; Paralytic shellfish toxin; Phenotype; Plant cytology, morphology, systematics, chorology and evolution; Plants and fungi; shellfish; Thallophyta; Tolerance; toxicity; toxins
• ISSN: 1568-9883; 1878-1470
• DOI: 10.1016/j.hal.2011.06.014

► Ingestion assays were designed to objectively segregate individual copepods by levels of phenotypic tolerance to paralytic shellfish toxins (PSTs). ► The assay is nonlethal and short-term, thus opening possibilities to further experimentation with the same animals once phenotypes have been defined. ► Results from this study suggest that populations may differ in their physiological tolerance to PSTs because they comprise tolerant individuals in varying proportions. Phenotypic tolerance of individual copepods to paralytic shellfish toxins (PSTs), as determined by fecundity, has recently been reported. In the present study, we tested whether similar phenotypic tolerance related to ingestion also exists. In short-term feeding assays, ingestion rates of individual females of the copepod Acartia hudsonica were measured on a sole diet of toxic Alexandrium fundyense as well as on a sole diet of nontoxic Alexandrium tamarense. When copepods fed on A. fundyense, the frequency distribution of ingestion rates was polymodal, consistent with the hypothesis of levels of phenotypic tolerance associated with toxin ingestion. Four distinct groups of ingestion rates on toxic algae were observed. Mean rates ranged from near zero to more than 100 cells copepod −1 h −1. In contrast, when the same individuals fed on the nontoxic A. tamarense diet, the polymodal distribution of ingestion rates was not apparent. Furthermore, group-specific mean ingestion rates, for two ingestion-defined groups, were always significantly greater on the toxic diet than they were on the nontoxic diet. These results support the hypothesis that discrete groups of grazer ingestion of toxic A. fundyense are related to PST tolerance.