Essential fatty acids for
larval mud crab Scylla serrata: implications of lack of the ability
to bioconvert C18 unsaturated fatty acids to highly unsaturated fatty acids
M. Agus Suprayudi, T. Takeuchi, K. Hamasaki-2004
Aquaculture, 231(1-4): 403-416
Abstract:
This study was conducted to examine the effect of
essential fatty acids (EFA) on the survival, development and bioconversion
of fatty acids in mud crab Scylla serrata larvae. Mud crab larvae
held in 1-l plastic beakers (30 ind/l) were fed rotifers that had been
enriched with oleic acid (18:1n-9, OA), linoleic acid (18:2n-6,
LA), linolenic acid (18:3n-3, LNA), eicosapentaenoic acid (20:5n-3,
EPA) and docosahexaenoic acid (22:6n-3, DHA) ethyl ester oil during
the zoea (Z)1 and Z2 stage. Upon reaching the Z3 stage, rotifers were
shifted to unenriched Artemia or Artemia enriched with either
EPA or DHA ethyl ester. Further in order to allow comparison of the effect
of the enriched rotifers on the fatty acid composition of the Z2 stage
larvae, larvae fed enriched rotifers were harvested upon reaching the Z2
stage for fatty acid analysis.
The survival of mud crab larvae was more strongly
affected by the EFA contained in the Artemia compared to rotifers.
Mud crab larvae fed unenriched Artemia showed EFA deficiency signs
such as lower survival, longer intermolt period, and a narrower carapace
width at the first crab stage, indicating that DHA was superior to that of
EPA and followed by LNA and LA. The fatty acid composition of the whole body
of Z2 larvae fed rotifers enriched with OA, LA or LNA revealed that the
content (g/100 g larvae) of EPA decreased from 1.2 to 0.4–0.8 and DHA
decreased from 0.5 to 0.1–0.2, respectively. Moreover, the contents of
monoenes increased from 1.4 to 2.5–3.2, indicating dietary EFA deficiency.
We conclude that mud crab larvae have a limited or negligible capability to
convert C18 unsaturated fatty acids to highly unsaturated fatty acids.
(Department of Aquatic Biosciences, Faculty of
Fisheries, Tokyo University of Fisheries, 4-5-7 Konan, Minato, Tokyo
108-8477, Japan, e-mail of T. Takeuchi: take@tokyo-u-fish.ac.jp)