The acute (30 min) responses of heart and scaphognathite activities of Crangon crangon on exposure to concentrations of 1-20 mg Cd, Cu or Zn 1-1 are increased beat frequencies. The relative magnitude of response (A f) is linearly related to immediate pretreatment frequency (f) and standardised responses (Afs) are given for f values of 70 and 100 beats min -I for hearts and scaphognathites, respectively. Afs values for each organ are also linearly related to test concentration for each metal. Qualitative changes to organ activities described include an increased incidence of scaphognathite reversals in concentrations of 5.0 mg Cu 1-1 and in 20.0 mg Zn 1-1. Chronic (13 days) exposure to incipient lethal levels of the test metals produced increases in scaphognathite rates of the Cd-treated animals and in heart and scaphognathite rates of the coppertreated animals. The general applicability of these methods to studies of pollution stress in decapods is discussed.

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