Synthetic sea water as a medium for raising crab larvae
© Biologischen Anstalt Helgoland 1973
1. Larvae of the xanthid crabRhithropanopeus harrisii (Gould), were raised from hatching through the megalopa in natural sea water, and in two commercially available synthetic sea salts. Groups of larvae from the same hatch were raised at two salinities for each medium.
2. Hatching occurred successfully in all six media-salinity combinations tested.
3. Survival was high through the four zoea stages in all six test solutions. Statistical tests on cumulative zoea mortality showed no significant differences due either to salinity or to medium, and no interaction between them.
4. Survival dropped during the megalopa in all test solutions. Megalopa mortality was significantly higher in 3 ‰ than in 11 ‰. Although differences in mortality among the three media were apparent, statistical tests showed only marginal significance. No interaction between salinity and medium was evident.
5. Rate of development through the zoea stages was affected by both salinity and medium although no interaction between these factors was evident. The following relationships among the six test solutions were demonstrated (from longest to shortest development): IO, 3‰=7-S, 3‰≧7-S, 11 ‰ nsw, 3 ‰=nsw11‰ = IO, 11‰
6. Differences among the three media in rate of megalopa development at 11 ‰ were only marginally significant (only one individual survived at 3 ‰).
7. It is concluded that either of the two synthetic media used is suitable for raising larvae ofRhithropanopeus harrisii.
8. The following criteria should be considered in choice of medium for raising larvae: influence on rate of development and survival, cost, specific ion composition, purity, and ease of preparation.