BAGATTO, B.P.*; BURGGREN, W.W.: Chronic Training Influences on Performance in Zebrafish Larvae, Danio rerio

Zebrafish larvae (Danio rerio) of an albino color mutant (alb/alb) were divided into three different age groups (4, 9, and 21 days post-fertilization) and subjected to a continuous training water velocity of 5 body lengths per second. From behavioral observations at rest, trained larvae from the oldest group were significantly less active, but swam with greater velocity compared to controls. Trained larvae also swam significantly longer during performance tests and thus covered more distance at faster velocities compared to controls. This suggests that some physiological change in the musculature and/or cardiovascular system is involved in order to impart improved performance on the trained larvae. Although trained larvae could swim longer until exhaustion, they did not produce any more lactate than controls, suggesting a similar lactate-induced anaerobic threshold. However, small but significant amounts of lactate were produced at slower swimming velocities in trained fish. These levels remained consistent at higher swimming velocities in trained larvae while the controls began to produce increased amounts of lactate and become debilitated. Therefore, training provided a definite swimming performance improvement. If muscles change in some morphological and/or physiological way, this may also reflect or augment changes in the cardiovascular system. Training also significantly increased resting cardiac output in all age groups of zebrafish larvae, primarily via increases in stroke volume. It is unknown at this time whether increased resting cardiac output is the result of training-induced increased muscle tissue metabolism and/or vasculature, or the result of direct cardiac effects (supported by NSF IBN 98-96388).