The Israeli Journal of Aquaculture - Bamidgeh 54(2), 2002
The Annual Dan Popper Symposium


THE EFFECT OF DIETARY ARACHIDONIC ACID ON SURVIVAL AND
CORTISOL LEVEL IN GILTHEAD SEABREAM (SPARUS AURATA ) LARVAE
EXPOSED TO STRESS CONDITIONS


Sigal Lutzky¹*, William Koven¹, Rogier Van Anholt², Isashar Ben-Atia¹, Ruth Weiss¹, Amos Tandler¹

1 Israel Oceanographic and Limnological Research, The National Center for Mariculture, P.O.Box 1212, Eilat 88112, Israel
2 Department of Animal Physiology, University of Nijmegen, Toernooiveld, 6525 ED, Nijmegen, The Netherlands


Abstract

This paper summarizes the effects of dietary arachidonic acid (20:4n-6, ArA) on survival in gilt-head seabream larvae exposed to handling, water turbulence, air exposure, crowding, temperature increase and salinity increase, and the possible metabolic pathways of ArA that are involved.

Initial studies demonstrated that dietary ArA markedly (p<0.05) improved survival of seabream larvae following handling stress, provided this essential fatty acid was fed prior to handling. Dietary ArA also promoted better survival of larvae stocked in aquaria at different densities (3, 6 and 12 larvae/l). Another feeding trial tested the effect of dietary ArA on the acute (handling) and chronic (daily fluctuating salinity) stress response of larvae during metamorphosis and postmetamorphosis. Results showed a clear correlation between dietary ArA, cortisol level and survival in larvae exposed to handling while a high level of dietary ArA fed to chronically stressed larvae led to increased mortality and markedly higher levels of cortisol. The data suggest that metamorphosing larvae are more sensitive to the effects of dietary ArA than postlarvae. This hypothesis was reinforced in further studies which investigated the effect of dietary ArA in larvae at different stages of development that were rapidly exposed to salinity increase, temperature increase, air exposure or water turbulence.

Accumulated results led to the hypothesis that the prostaglandin PGE2, derived from ArA, was involved in regulating cortisol synthesis through the hypothalamus-pituitary-interrenal (HPI) axis during a stress event. However, recent findings also suggest that free ArA may directly mediate the stress response as well.

*Corresponding author. Fax: 972-8-6375761, e-mail: gali@ocean.org.il

home