The effects of emersion stress upon circulating hyperglycaemic hormone (CHH) levels in the edible crab Cancer pagurus were investigated using a highly specific and sensitive radioimmunoassay, with an antiserum directed against HPLC-purified C. pagurus CHH. Emersion resulted in hyperglycaemia and immediate hypoxia, as shown by rapid hyperlactaemia. CHH levels increased dramatically during the first hour of emersion, from almost undetectable levels to around 17 pmol l-1, thereafter increasing to around 30 pmol l-1 after 4 h of emersion. Short-term air exposure experiments demonstrated that significant increases in CHH levels (up to 3.5 pmol l-1) could be detected during the first 15 min of emersion. Although CHH appears to be fairly stable in haemolymph in vitro, injected CHH was cleared extremely rapidly from the haemolymph in vivo. The results suggest that emersion results in rapid, massive and prolonged exocytosis of CHH from the sinus gland. The sensitivity of the assay and the utility of this crab model may be useful in further studies to elucidate the control of CHH release in crustaceans.

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