KING, A.J.*; SCHMIDT, M.H.; ADAMO, S.A.; Dalhousie University, Halifax; IWK Health Sciences Centre; Dalhousie University, Halifax: The first use of ultrasound to image cardiovascular and respiratory structures in cuttlefish (Sepia officinalis, class Cephalopoda)

Cephalopods have elevated metabolic rates and cardiovascular systems that are surprisingly similar to those of vertebrates. Oxygen transport, however, is constrained by low blood oxygen content and viscous blood. We used ultrasound to investigate the coordination of respiratory and cardiovascular movements in cuttlefish (Sepia officinalis, class Cephalopoda) while they rested and while they reacted to a model predator. Ultrasound provides the first non-invasive way to monitor cardiovascular function in cuttlefish. In cuttlefish, the muscular mantle pumps water over the gills and encloses the investigated vasculature (cephalic vein, venae cavae, efferent brachial vessel, auricles, ventricle). Its rhythmic contractions, therefore, could influence cardiovascular vessels by compressing them. When resting, we found that cuttlefish gills and one section of the cephalic vein contracted at the same time as the mantle. The systemic heart, venae cavae and efferent gill vessels, however, contracted independently of the mantle. These results suggest that while mantle movements might influence cardiovascular flow by forcing blood out of the tissue, they do not cause most vessels to contract. When exposed to a model predator, our cuttlefish flattened their bodies and became almost motionless (deimatic behavior). While flattened, cuttlefish dramatically slowed or stopped mantle movements as well as cardiovascular contractions for 2-20s (n=2, 5/5 trials). During resting ventilation, vessels can pulse even during mantle contractions. Therefore, the decrease in cardiovascular function while the mantle contracts and flattens is unlikely due to a constraint imposed by pressure from the mantle.