Cardiovascular performance is altered by temperature in larval fishes, but how acute vs. chronic temperature exposures independently affect cardiac morphology and physiology in the growing larva is poorly understood. Consequently, the influence of water temperature on cardiac plasticity was investigated in developing mahi-mahi. Morphological (e.g. standard length, heart angle) and physiological cardiac variables (e.g. heart rate fH, stroke volume, cardiac output) were recorded under two conditions by imaging: i) under acute temperature exposure where embryos were reared at 25°C up to 128 hours post-fertilization (hpf) and then acutely exposed to 25° (rearing temperature), 27° and 30°C; ii) at two rearing (chronic) temperatures of 26° and 30°C and performed at 32 and 56 hpf. Chronic elevated temperature improved developmental time in mahi. Heart rate were 1.2-1.4-fold higher under exposure of elevated acute temperatures across development (Q10≥2.0). Q10 for heart rate in acute exposure was 1.8-fold higher compared to chronic exposure at 56 hpf. At same stage, stroke volume was temperature independent (Q10∼1.0). However, larvae displayed higher stroke volume later in stage. Cardiac output in developing mahi is mainly dictated by chronotropic rather than inotropic modulation, is differentially affected by temperature during development and is not linked to metabolic changes.
- Received March 22, 2017.
- Accepted April 18, 2017.
- © 2017. Published by The Company of Biologists Ltd
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