THE DIFFERENTIAL EFFECT OF n-3
HUFA AND ARACHIDONIC ACID (20:4n-6) ON THE CORTISOL RESPONSE AND
SURVIVAL OF SEABASS (Dicentrarchus labrax) LARVAE
EXPOSED TO RAPID SALINITY CHANGE AND AIR EXPOSURE
W. Koven, S. Lutzky, O. Nixon, R. van Anholt, I.
Ben-Atia, M. Torten, A. Tandler
The effect of dietary n-3 HUFA
and ArA on survival and cortisol levels of seabass larvae exposed
to rapid salinity change or air exposure was tested. Larvae from 24-33 DAH
in twenty-five
27 1 aquaria (250 larvae/aquaria) were fed five Artemia treatments (5 aquaria/treatment)
where three treatments had low, medium and high levels of arachidonic acid
but contained moderate amounts of n-3 HUFA while two treatments had low and
high levels of n-3 HUFA and contained low levels of ArA. On 34 DAH, larvae
from each aquaria were transferred to 250 ml plastic cups containing 8, 25 or
40 %o seawater where the mortality was
monitored over 2 h and remaining larvae analyzed for whole body cortisol.
Separately, same-age larvae from each aquaria were exposed to air for
60 sec and then transferred to 250 ml plastic cups (ambient 25 %o
seawater)
where larval mortality was monitored over 2 h and the
remaining larvae analyzed for whole body cortisol. Seabass larvae did not
exhibit significant stress-related mortality in any of the
treatments. On the other hand, cortisol levels in air-exposed larvae
clearly correlated with increasing dietary ArA. However, cortisol levels in
air-exposed larvae fed enhanced n-3 HUFA decreased. The implications for
aquaculture are discussed.
(Israel
Oceanographic and Limnological Research, The National Center for
Mariculture, P.O. Box 1212, Eilat 88112, Israel)