Defenses Against Solar Ultraviolet Radiation-induced Photooxidative Stress in Sea Urchins: Dietary Accumulation and Functions of Mycosporine-like Amino Acids

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The regulation of defenses against solar ultraviolet radiation- induced photooxidative stress in sea urchins will be studied. Like other marine organisms, sea urchins contain mycosporine-like amino acids (MAAs), which absorb environmentally relevant wavelengths of UV (310-360 nm). MAAs are presumably algal, bacterial or fungal products, animals not being known to synthesize them, so their provenance in sea urchins is uncertain. Various seaweeds are rich in MAAs, and preliminary chromatographic analyses indicate concordance between the MAA complements in seaweeds and in sea urchin tissues, especially ovaries. Maintenance of sea urchins on controlled diets of seaweeds lacking or rich in MAAs, subsequent analysis of gut contents and tissues, testing the ability of gut tissues to absorb MAAs should confirm whether MAAs are so obtained. Dietary fortification of sea urchin ovaries should confer a greater resistance to UV in eggs and larvae, and UV effects on fertilization, development, and larval survival will be assessed in MAA-rich and deficient specimens. It is also planned to discern the particular membrane fractions. Possible radical scavenging functions of gadusol (structurally similar to MAAs) present in eggs will be assessed in parallel experiments, since some UV effects are mediated by oxyradicals. The results will have implications for the mechanism of accumulation of photooxidative defenses in marine food chains, a genuine concern as the protective ozone layer deteriorates.