The dual functions of sea urchin gonads are reflected in the temporal variations of their biochemistry
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Fatty acid analyses are emerging as a powerful technique to probe trophic interactions between organisms. In this paper, the application of both this procedure and gonad index (GI) determination on two populations (intertidal and subtidal) of the echinoid Psammechinus miliaris is reported. The investigation spanned the 3-month spawning period of Scottish west coast populations. In both populations a progressive decrease in the GI was found, coupled with an increasing maturity stage (from mature to spent). Sexual maturation and decrease in GI was synchronous between the two populations. In conjunction, there were distinct changes in gonad biochemistry. Differences in the fatty acid composition of the gonad reflected the changes in sexual maturation. Mature males and females had significant differences in the fatty acid composition of their gonads, whereas post-spawned individuals showed no gender differences. Male urchins had higher levels of polyunsaturated fatty acids (PUFAs) compared to females, and there was a dramatic reduction in the fatty acids 22:6(n−3) and 20:5(n−3) with increasing maturity stage. Using multivariate statistical techniques, these changes in the fatty acid composition of the sea urchin gonad were linked to habitat related diet differences combined with gender differences. These changes in the fatty acid signatures clearly reflect the dual function of the gonad as both a nutrient store and a reproductive organ.
KeywordsFatty Acid Composition Maturity Stage Fatty Acid Analysis Female Gonad Gonadal Index
The authors would like to thank Dr. E. Cook for her help and Miss H. Muir for her technical support with the fatty acid analysis. They would also like to thank M.V. Bell for his helpful comments on an earlier draft of this manuscript. We would also like to acknowledge the Leonardo da Vinci scholarship for facilitating the visit of AIC to SAMS. This research was funded through the NERC Ph.D. studentship NER/S/A/2002/1055.
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