Dear MARMAM community, On behalf of all authors, I am pleased to share our study on cardiorespiratory patterns of South American sea lions. PDF copies are available upon request to Carolina de León (de.leon.carito@gmail.com) Cheers Diego Rodríguez De León, M. C., Rodríguez, D. H., & Dassis, M. (2024). Cardiorespiratory patterns of male South American sea lions (Otaria flavescens) resting on land. Journal of Comparative Physiology B, 1-13. https://link.springer.com/article/10.1007/s00360-024-01533-9 Abstract The goal of this study was to characterize the cardiorespiratory patterns of male South American sea lions (SASLs, Otaria flavescens) resting on land. We recorded respiratory and heart rate (n = 360 individuals studied) by observing the nostrils, chest movements and the impact of the heart on the thoracic wall. The sea lions breathe apneustically with a pause on inspiration, representing 74% of the respiratory cycle. The mean breathing frequency was 3.2 ± 1.0 breaths min−1, with a breathing cycle presenting periods of bradypneas, tachypneas, and long-term post-inspiratory pauses. The normal heart rate (nHR) was 73.4 ± 14.5 beats min−1 and no significant differences were observed between age classes. All animals showed variability in HR in relation to respiratory phases (Inspiration: 101.2 ± 18.4 beats min−1; post-inspiratory pause: 73.4 ± 14.5 beats min−1; expiration: 64.6 ± 17.7 beats min−1), consistent with respiratory sinus arrhythmia (RSA). The mean HR (measured during all respiratory phases) was 79.9 ± 22.7 beats min−1, and was significantly different between age classes. The total duration of respiratory cycle, and duration of both inspiration and expiration, decreased with an increment in ambient temperature, with no variation in the pause duration. Heart rate during pause and expiration was significantly higher during high temperatures. Similar changes in cardiorespiratory patterns have been reported in other pinnipeds. Our results showed ontogenetic differences in development and typical variations with environmental and behavioral variables. -- Dr.Diego Rodríguez Instituto de Investigaciones Marinas y Costeras, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata-CONICET. Casilla de Correos 1260 (Correo Central) (7600) Mar del Plata, Argentina TE + 54 (0) 223 4754060 (Int.244) FAX +54 (0) 223 4753150 Skype: diego291162 Facebook: http://www.facebook.com/groups/136323163081610/ Website: https://www.researchgate.net/profile/Diego_Rodriguez16 ORCID ID: https://orcid.org/0000-0002-5080-3739 "Si los pueblos no se ilustran, si no se divulgan sus derechos, si cada hombre no conoce lo que puede, vale, debe, nuevas ilusiones sucederán a las antiguas y será tal vez nuestra suerte cambiar de tiranos sin destruir la tiranía" (Mariano Moreno)