MCHENRY, Matthew/J; LAUDER, George/V; Harvard Univ.; Harvard Univ.: How do ontogenetic changes in morphology, behavior, and hydrodynamics affect the performance of gliding in zebrafish?

As fish grow from larvae to adults, changes in their morphology and behavior cause unpredictable alterations in swimming performance. On example of such ontogenetic change is provided by the routine beat-and-glide swimming of zebrafish. During the glide phase, adult zebrafish traverse a disproportionately longer distance in the same time as larvae. The present study examined the ontogenetic scaling of morphology, behavior and hydrodynamics in zebrafish (Danio rerio) in order to understand why adult zebrafish glide disproportionately further than larvae. Adult zebrafish begin the glide stage at a disproportionately faster speed and this speed decays at a slower rate than in larvae. This difference in the decay of speed is not predicted under the assumption that adults and larvae have the same drag coefficient and function in the same hydrodynamic regime. In order to test whether zebrafish change either drag coefficient or hydrodynamics during growth, we directly measured the drag acting on the bodies of dead fish and chemically altered the viscosity of water to manipulate the hydrodynamics of freely swimming fish. Our results suggest that ontogenetic changes in glide distance are mediated largely by a combination of hydrodynamic and behavioral changes over ontogeny.