Effects of salinity and dietary n-3 highly unsaturated fatty acids on the survival,development, and morphogenesis of the larvae of laboratory-reared mud crab <Emphasis Type="Italic">Scylla serrata</Emphasis> (Decapoda,Portunidae) |
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| Authors: | Shigeki Dan Katsuyuki Hamasaki |
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| Institution: | (1) Tamano Station, National Center for Stock Enhancement, Fisheries Research Agency, Tamano, Okayama 706-0002, Japan;(2) Department of Marine Biosciences, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan; |
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| Abstract: | We investigated the effects of feeding rotifers containing various levels of n-3 highly unsaturated fatty acids (n-3HUFA)
to Scylla
serrata larvae at different developmental stages on their survival, development, and morphogenesis when they were cultured at six
salinity levels. The first-, third-, and fifth (last)-stage zoeae and megalopae were reared to first-stage crabs at salinities
of 10, 15, 20, 25, 30, and 35‰, with three different feeding regimes of rotifers containing different levels of n-3HUFA. The
larvae successfully developed to the subsequent stages at 20–35‰ salinity. The highest survival rates to first-stage crabs
were recorded at 20–25‰ salinity. The morphological features of the megalopa observed in the last-stage zoeae, represented
by the ratio of the chela length to carapace length, tended to advance with increasing salinity, indicating higher assimilation
efficiency at higher salinities. The megalopal features of the last-stage zoeae were enhanced when the larvae were fed rotifers
containing higher amounts of docosahexaenoic acid (DHA). As reported previously, final-stage zoeal larvae with advanced megalopal
features often experienced moult death syndrome (MDS). These results show that when larvae are fed rotifers with high DHA
under high-salinity conditions, morphogenesis is accelerated, resulting in MDS. Therefore, to evaluate the effects of salinity
on larval survival, it is necessary to examine larval morphogenesis in terms of MDS. In conclusion, we recommend that not
only survival but also larval morphogenesis should be examined when evaluating the results of rearing experiments with S. serrata larvae. |
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