Body colour response of the carp (Cyprinus carpio) during asphyxia

The body colour of immobilized carp was photoelectrically measured simultaneously with heart rate in order to examine one of the effects of asphyxia on autonomic functions of the cutaneous region. 1) Asphyxia induced marked body colour darkening and bradycardia. 2) Adequate increase in cardiac vagal activity was recorded during asphyxic bradycardia. 3) After atropine injection, body colour darkening, as in intact fish, was observed during asphyxia while heart rate was not changed. 4) After transection of anterior spinal cord, asphyxic stimulation did not induce body colour darkening. It is concluded that body colour darkening mediated by nervous pathways was observed during asphyxia simultaneously with the definite bradycardia. This response of body colour has provided the first indication for responses in cutaneous autonomic systems within the responses of the fish co-ordinated as a whole to asphyxia.