The ventilatory, cardiac and behavioural responses of resting cuttlefish (Sepia officinalis L.) to sudden visual stimuli.

When startled, some animals reduce ventilation rate and heart rate, and become motionless. The function of this response, if any, remains unknown. We used non-invasive ultrasound imaging to monitor the ventilatory, cardiac and postural responses of cuttlefish exposed to sudden visual stimuli. Simultaneously, we recorded cuttlefish behaviour using an overhead video camera. Upon presentation of the sudden visual stimulus (rapidly approaching bird cut-out), cuttlefish rapidly changed the colour and the texture of their skin, taking on characteristics of the Deimatic Display. Cuttlefish also became motionless (behavioural freezing), hyperinflated their mantles, and decreased their ventilation rate and heart rate. We found no evidence of a relationship between the intensity of the Deimatic Display and the intensity of any other measured parameter. Ventilation rate decreased during behavioural freezing. Hyperinflation of the mantle was most intense in preparation for and during behavioural freezing. Heart rate decreases occurred during mantle hyperinflation and were greatest in animals showing the most hyperinflation. Decreased heart rate may not be adaptive per se. Instead, it might be a product of the unusual arrangement of the cuttlefish peripheral vasculature, which could be compressed during mantle hyperinflation. By filling the mantle with water (hyperinflation), this response to sudden stimuli may help cuttlefish prepare for possible flight by jet propulsion, which often follows the Deimatic Display.