As global warming increases it is becoming more and more important to understand how higher temperatures will affect both aquatic and terrestrial animals. A recent study, published by a research group from Rhodes University and the South African Institute for Aquatic Biodiversity in South Africa, used Star-Oddi heart rate loggers to try to determine the cardiac breaking point of a species of marine sparid (Chrysoblephus laticeps).

Heart rate measured during an acute warming event
Nine fish were implanted with Star-Oddi’s DSTmicro-HRT leadless heart rate and temperature logger. The loggers were set to measure heart rate and temperature every 15 seconds at 150Hz during the challenge. In addition, heart rate was measured using external electrodes, a method that is difficult to carry out in saltwater. After recovery, fish were put through an acute warming event.

Ecologically relevant results
Five out of the nine fish provided accurate maximum heart rate data. This data was used to find the Arrhenius break temperature (T_AB) which is the temperature where maximum heart rate no longer scales predictably with warming. The T_AB was found to be ecologically relevant, suggesting that implantable heart rate loggers are a reliable way to estimate T_AB of marine animals.

The paper was published in The Journal of Thermal Biology and can be accessed here.

Photo by Pbsouthwood at wts wikivoyage