Observations on undisturbed, individually isolated, Octopus vulgaris Cuvier show that
ventilation rate is strongly related to “arousal” or activation. Ventilation rate may be recorded
visually by a screened observer or remotely, using carbon electrodes connected to a pen
recorder via an impedance coupler to register the associated water movements in a small
experimental chamber. The method allows a quantifiable behavioural characteristic to be
measured objectively. It has been used to demonstrate that O. vulgaris responds to certain …