Mycosporine-like amino acids prevent UVB-induced abnormalities during early development of the green sea urchin Strongylocentrotus droebachiensis

Experiments were performed to determine how ultraviolet radiation (UVR) in the environmentally relevant range affects development of the sea urchin St rongylocentrotus droebachiensis (Muller) and whether mycosporine-like amino acids (MAAs), present in the early life stages, reduce UV-induced damage. Eggs, embryos, and larvae contained five MAAs having absorption maxima rang ing from 320 to 334 nm. Eggs contained principally shinorine and porphyra-3 34, which absorb maximally at 334 nm and half-maximally at 312 and 348 nm, spanning much of the environmental range of biologically effective UVR. Con centrations of MAAs remained constant in unirradiated embryos through the g astrula stage, but decreased significantly in two-armed pluteus larvae. Dai ly exposure to combined photosynthetically active radiation (PAR, 400-700 n m) and UVR did not affect the concentration of MAAs in these embryos up to the two-armed pluteus stage. Prism larvae of sea urchins and the sand dolla r Echinarachnius pal mn (Lamarck) did not accumulate shinorine from the sur rounding seawater. Daily exposure of embryos to UVA (320-400 nm) and UVB (2 95-320 nm) radiation in the presence of PAR induced delays and abnormalitie s during development, and removing UVB eliminated this effect. Abnormalitie s in embryos included thickening of the blastoderm wall, filling of the bla stocoel by abnormal cells, exogastrulation, and formation of abnormal spicu les. The percentage of embryos that developed normally was lower in batches of embryos exposed to PAR + UVA + UVB, except in embryos from urchins main tained on MAA-rich diets. In all cases, the percentage of PAR + UVA + UVB-e xposed embryos that developed normally was positively related to the concen tration of MAAs in eggs from which the embryos developed. Thus, the MAAs fo und in S. droebachiensis embryos protect them against UVB-induced abnormali ties during their development to at least the four-armed pluteus larval sta ge.