Meeting Abstract
Larval fish suffer dramatic mortality in the days following transition to autonomous feeding, with over 90% of larvae being eliminated within a period of a few weeks. Recent work has shown that the hydrodynamic environment experienced by recently-hatched larvae impedes their feeding rates even under high prey densities. To determine whether these low feeding rates result in acute starvation during this “critical period”, we quantified the expression of agrp1 and npy, two hypothalamic orexigenic (appetite-stimulating) neuropeptides whose expression increases upon starvation. The expression of both neuropeptides was quantified in Sparus aurata larvae throughout early development (8-23 days post-hatching). Localization of the neuropeptides’ mRNA by whole-mount in-situ hybridization confirmed that, in S. aurata larvae, they are expressed only in the hypothalamus. Quantification of both neuropeptides mRNA using Real-time PCR revealed that the expression of this gene is elevated in starved S. aurata larvae compared to fed ones. Manipulating the water viscosity to simulate the hydrodynamic conditions during the onset of the critical period led to increased agrp1 and npy expression. These findings suggest that the hydrodynamic constraints on larval feeding lead to the starvation of small larvae, likely reflecting their state in the natural pelagic habitat.
