post-hatching. Although larval fatty acid profiles reflected the enrichment treatments, there were Ž
. no marked differences P 0.05 in survival and growth in 5–19 day old larvae at the end of
rotifer feeding. However, the larvae fed the AA enriched rotifers prior to the handling stress of Ž
. transfer to the aquaria demonstrated daily and significantly
P - 0.05 lower accumulated
Ž .
mortality after transfer and during Artemia feeding than larvae fed the AA-deficient DHA-PL and ALGA-enriched rotifers. As larvae fed the ALGA, rotifers partially retroconverted DPA to
Ž .
Ž .
AA in their tissues, the final survival 31.0 in these larvae was markedly better P - 0.05 than Ž
. Ž
. larvae fed the DHA rotifers 17.5 , but significantly
P - 0.05 lower than larvae ingesting Ž
. AADHA rotifers 42.9 . Conversely, the high-accumulated mortality in larvae fed the AA-defi-
cient rotifers could not be corrected during the post-handling phase by feeding AA supplemented Artemia. The results suggest that dietary AA fed prior to handling stress improved survival more
effectively than when fed following handling stress. These findings imply, as well, the importance of early larval nutrition on later larval and juvenile survival during crowding, grading and other
handling stressors. q 2001 Elsevier Science B.V. All rights reserved.
Keywords: Stress resistance; Essential fatty acid; Arachidonic acid; Docosahexaenoic acid; Marine fish larvae; Eicosanoids; Survival
1. Introduction
The essential dietary requirement in many marine teleosts for the long chain Ž
. Ž
. polyunsaturated fatty acids
PUFA , docosahexaenoic acid DHA, 22:6 n y 3
and Ž
. Ž
eicosapentaenoic acid EPA, 20:5n y 3 has long been established Kitajima et al., 1980a,b; Watanabe et al., 1983a,b; Kanazawa, 1985; Izquierdo et al., 1989, Koven et al.,
. 1989, 1990, 1992a; Izquierdo, 1996 . These fatty acids, as components of phospholipids,
function as critical structural and physiological components of the cell membranes of Ž
. most tissues Gurr and Harwood, 1991; Sargent et al., 1993a . DHA, in particular, has
high biological value during larval development and is selectively incorporated into the neural tissues contributing to pigmentation, visual acuity and presumably prey hunting
Ž success Koven et al., 1992b; Kanazawa, 1993; Sargent et al., 1993b; Watanabe, 1993;
. Bell et al., 1995 . A dietary deficiency in DHA in larvae of farmed marine teleosts has
been correlated with poor growth, high mortality and susceptibility to stress and disease Ž
. Waagboe et al., 1993; Kiron et al., 1995; Lingenfelser et al., 1995 . In general, and
unlike their freshwater counterparts, marine fish larvae lack D
5
desaturase rendering them unable to synthesize DHA and EPA from the shorter PUFA precursor linolenic
Ž .
acid 18:3n y 3 . As a consequence, commercial preparations routinely used to enrich Ž
. the live food rotifers and Artemia nauplii of the larval stages of cultured marine
teleosts, contain abundant amounts of DHA, together with relatively lower levels of EPA.
However, little attention has been given to the PUFA of the n y 6 series, despite broad hints in the literature attesting to its potential importance. Quantitatively, these
fatty acids are much less represented in the tissues of marine fish where lipids can Ž
. typically have an n y 3rn y 6 ratio of 10–15:1 Ackman, 1980 . Despite this discrep-
ancy in cellular membrane levels, studies have suggested that the long chain n y 6 Ž
. PUFA, arachidonic acid AA, 20:4 n y 6 , is also essential for certain marine fish
Ž .
Ostrowski and Divakaran, 1990; Castell et al., 1994; Bessonart et al., 1999 . Workers have reported that AA was preferentially retained in various species together with DHA
during starvation, suggesting a metabolic priority for conservation of certain fatty acids Ž
. Ostrowski and Divakaran, 1990; Rainuzzo et al., 1994; Izquierdo, 1996 . In turbot,
Ž dietary deficiencies in AA have resulted in high mortality and obvious pathology Bell
. Ž
. et al., 1985a , while Castell et al. 1994 reported a positive effect of AA on survival
Ž .
from levels ranging from 0.5–1.0. Bessonart et al. 1999 found that AA was more effective in improving survival of gilthead seabream larvae if provided in the presence
of a high dietary DHArEPA ratio. On the other hand, AA supplementation may also have adverse affects. Other studies on turbot and halibut found an increased incidence of
malpigmentation correlated with brain AA, whereas higher EPArAA dietary levels
Ž .
improved pigmentation McEvoy et al., 1998 . The above findings suggest that AA contributes to survival in larvae of a variety of
marine teleosts. However, the question remains whether AA is equally effective throughout larval development. Moreover, due to the possible effect of AA-based
eicosanoids on cortisol production during stress, the dietary AA effect on survival may be related to stress resistance. Consequently, the aim of the present study on the larvae
of the gilthead seabream was twofold. Firstly, to test the effect of dietary AA on growth and survival in early and late larval development. Secondly, to determine the influence
of dietary AA on larval growth and survival, prior to andror following handling stress.
2. Methods and materials
