Effect of temperature on heart rate in diploid and triploid brook charr, Salvelinus fontinalis, embryos and larvae

Increased cell size in triploid fish likely affects rates of respiratory gas exchange. Respiratory deficiencies can be addressed in fish by adjustments in cardiac output, through changes in heart rate and stroke volume. The aim of this study was to determine whether heart rate differs between triploid and control (diploid) brook charr, Salvelinus fontinalis, at embryo–larval stages, when the heart is easily visible and the fish are relatively inactive. Heart rate was measured at 6, 9 and 12 °C at three developmental stages: eyed-egg, hatch and yolk absorption. Heart rate was unaffected by ploidy, but increased with temperature and age from a low of 43.4 ± 2.2 beats/min (6 °C, eyed egg) to a high of 73.3 ± 1.5 beats/min (12 °C, yolk absorption). The Q10 for heart rate was unaffected by ploidy and age, but decreased with temperature from 1.99 ± 0.28 at 6–9 °C to 1.72 ± 0.17 at 9–12 °C. Triploid brook charr thus do not use adjustments in heart rate as a mechanism to deal with the physiological consequences of altered haematology at embryo–larval stages.