Effects of ultraviolet radiation and visible light on the development of encapsulated molluscan embryos

Abstract

Benthic egg masses laid in intertidal habitats are exposed to numerous environmental stresses including potentially damaging ultraviolet radiation (UVR). We sought to determine the developmental effects of UVR and visible light on molluscan embryos within egg masses from habi- tats with differential UVR exposure. Capsular and gelatinous egg masses from 23 marine gastropod species were collected from 3 intertidal habitats: (1) full sun, (2) partial shade, and (3) full shade. Egg masses were then divided among 4 spectral treatments: full spectrum, no UV-B, no UV, and dark. An ANOVA confirmed that a significant interaction between original habitat and spectral treatment affected mortality. Egg masses from full shade habitats showed significant vulnerability to UVR and visible light and had a higher overall mortality than other egg masses. Egg masses that were origi- nally partially shaded did not show any significant mortality differences among spectral treatments, but highest mortalities occurred in full spectrum treatments while lowest mortalities occurred in dark treatments. Egg masses from full sun habitats showed no significant mortality differences between spectral treatments, which is consistent with protection against the harmful effects of UVR. In addi- tion, the encapsulation period of egg masses in the dark was longer than the other 3 light treatments irrespective of habitat.