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Aquaculture 184 2000 155–166 www.elsevier.nlrlocateraqua-online
The use of larval fatty acids as an index of growth in Mytilus edulis L. larvae
Nikos Leonardos , Ian A.N. Lucas
1 School of Ocean Sciences, Menai Bridge LL59 5EY, N. Wales, UK
Accepted 16 September 1999
Abstract
Continuous cultures of Chaetoceros muelleri, Skeletonema costatum and Rhinomonas reticu- lata of controlled biochemical compositions were fed to Mytilus edulis larvae over a 2-week
period and the larval growth was assessed. The eggs as well as the larvae which subsequently developed were analyzed for their relative fatty acid profile and content; 27 fatty acids were
identified by means of GCrMS. Larval 15:0 and saturated fatty acids, in general, were found to be negatively correlated with larval growth, while polyunsaturated and n y 3 fatty acids were
positively correlated with growth. It is therefore proposed that the proportions of certain fatty acids and groups of fatty acids may be used as indices of growth and condition in M. edulis
larvae. q 2000 Elsevier Science B.V. All rights reserved.
Keywords: Fatty acids; Growth — larvae; Mytilus edulis; Skeletonema costatum; Rhinomonas reticulata
1. Introduction
In various bivalve larvae nutritional studies, larvae have been used to bioassay the Ž
nutritional value of algal, bacteria, yeast or artificial diets Laing, 1987; Brown et al., .
1996; Thompson et al., 1996 . However, different larval batches may have had inher- ently different survival or growth characteristics depending on broodstock origin.
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Variation in genetic composition Del Rio-Portilla, 1996 and broodstock nutrition,
Corresponding author. Vochtingstr 1-7, D-72076 Tubingen, Germany. E-mail:
¨ ¨
nikos.leonardostuebingen.mpg.de
1
Also corresponding
author. Tel.:
q44-1248-382871; fax:
q44-1248-382871; e-mail:
oss066bangor.ac.uk. 0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved.
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conditioning and stage of the gonadal cycle may thus make comparisons of algal nutritional value assayed in this manner difficult to interpret.
Growth and survival of bivalve larvae is strongly influenced by broodstock condition- ing in a number of ways. Seasonal variation in environmental conditions, with resulting
variation in the stage of gonadal development, will in turn influence the subsequent Ž
. gamete viability Lannan et al., 1980 . The correlation of broodstock conditioning and
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larval survival and growth was shown by Gallager and Mann 1986 to be characterized by the lipid content of the eggs. They found that variations in the broodstock condition-
ing protocol could produce large fluctuations in the lipid content of the eggs, thus providing the link between broodstock conditioning and larval survival and growth.
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Wilson et al. 1996 suggested that broodstock nutrition was also important for the Ž
. viability of the larvae of Ostrea chilensis, while Berntsson et al. 1997 have demon-
strated the effect of broodstock diet on fatty acid composition, survival and growth rates in larvae of O. edulis. They found that the larval growth rate was significantly correlated
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with the content of the total polyunsaturated fatty acids PUFAs and especially the 22:6 n y 3 representative. It has been suggested that lipid can be used as an index of
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growth and viability in the larvae of three species of bivalve Gallager et al., 1986 and has been proposed more widely as a condition index for fish and crustacean larvae
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Fraser, 1989 . Despite these reports, there is little conclusive evidence to suggest a correlation between larval fatty acids and growth.
In the present report, three microalgal species were grown under controlled condi- tions to produce cells of known biochemical composition. These diets were then
supplied to Mytilus edulis larvae for a 14-day feeding period. The fatty acid content of the larvae was assessed, as was their final length. These data were examined to
investigate if groups of larval fatty acids could be correlated with growth in M. edulis larvae. To insure that the resulting fatty acid variation was a result of the different
feeding diets and not due to the inherent biochemical variability of the larval batches, the corresponding egg batches were also analyzed for their fatty acid content. The larval
fatty acid results from the various trials were pooled for statistical analysis, provided there was agreement in the composition of the original eggs.
2. Materials and methods
