Summary: | The following research deals with the response of the small shore crabs, Hemigrapsus oreqonesis and Hemigrapsus nudus to paralytic shellfish toxins (PST). These shore crabs were shown to develop a remarkable seasonal resistance to administered saxitoxin (STX). No similar change in sensitivity was found after administration of tetrodotoxin (TTX), another marine neurotoxin with similar actions to the PST. Resistance to STX in the small shore crabs was linked to the presence of PST in the viscera, and this in turn was related to the presence of toxic dinoflagellate blooms in the area. Furthermore, this research provides, for the first time, evidence of a protein component (MW 145,000 daltons) which appears to be associated with acquired resistance to PST in the shore crab. In addition, this protein component was shown to appear in sensitive crab extracts after the administration of low doses of saxitoxin and tetrodotoxin in vivo. === Land and Food Systems, Faculty of === Graduate
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