Dear MARMAM community, We would like to share our new publication on cardiac function and cardiorespiratory coupling in cetaceans. In this study, the function of the heart was investigated in the bottlenose dolphin, the beluga, the killer whale, the false killer whale, and the pilot whale. The results showed that cetaceans have large variation in heart rate directly after a breath, and when compared with land mammals, the relationship between breathing frequency and heart rate is very different. We propose that these differences may indicate a mechanism that helps improve gas exchange during a surface interval. Fahlman, A., Miedler, S., Marti-Bonmati, L., Ferrero Fernandez, D., Muñoz Caballero, P., Arenarez, J., Rocho-Levine, J., Robeck, T., and Blawas, A.M. (2020). Cardiorespiratory coupling in cetaceans; a physiological strategy to improve gas exchange? Journal of Experimental Biology 223, jeb226365. Video abstract: https://www.youtube.com/watch?v=WxqKniwIVf4 <https://www.youtube.com/watch?v=WxqKniwIVf4> Abstract: In the current study we used transthoracic echocardiography to measure stroke volume (SV), heart rate ( fH) and cardiac output (CO) in adult bottlenose dolphins (Tursiops truncatus), a male beluga whale calf [Delphinapterus leucas, body mass (Mb) range: 151–175 kg] and an adult female false killer whale (Pseudorca crassidens, estimated Mb: 500–550 kg) housed in managed care.Wealso recorded continuous electrocardiogram (ECG) in the beluga whale, bottlenose dolphin, false killer whale, killer whale (Orcinus orca) and pilot whale (Globicephala macrorhynchus) to evaluate cardiorespiratory coupling while breathing spontaneously under voluntary control. The results show that cetaceans have a strong respiratory sinus arrythmia (RSA), during which both fH and SV vary within the interbreath interval, making average values dependent on the breathing frequency ( fR). The RSA-corrected fH was lower for all cetaceans compared with that of similarly sized terrestrial mammals breathing continuously. As compared with terrestrial mammals, the RSA-corrected SV and CO were either lower or the same for the dolphin and false killer whale, while both were elevated in the beluga whale. When plotting fR against fH for an inactive mammal, cetaceans had a greater cardiac response to changes in fR as compared with terrestrial mammals.We propose that these data indicate an important coupling between respiration and cardiac function that enhances gas exchange, and that this RSA is important to maximize gas exchange during surface intervals, similar to that reported in the elephant seal. The journal provides a couple of free downloads that can be found here: https://jeb.biologists.org/content/jexbio/223/17/jeb226365.full.pdf?ijkey=zK... <https://jeb.biologists.org/content/jexbio/223/17/jeb226365.full.pdf?ijkey=zKzvXDpWjAFqTvV&keytype=finite> Or else please send me an email if you would like a pdf copy at: afahlman@whoi.edu