Nikki L. Adams

Mycosporine-like Amino Acids Provide Protection Against Ultraviolet Radiation in Eggs of the Green Sea Urchin Strongylocentrotus droebachiensis

A photoprotective role of ultraviolet radiation‐absorbing mycosporine‐like amino acids (MAAs) in eggs of the green sea urchin Strongylocentrotus droebachiensis was demonstrated by comparing UV‐induced delays in the first division of embryos having either high or low concentrations of MAAs. Embryos from adult urchins fed Laminaria saccharina (no MAAs) had low concentrations of MAAs and experienced a significantly longer UV‐induced delay in cleavage (25.1%) than MAA‐rich embryos from adults fed Mastocarpus stellatus (12.8% delay) or a combination diet of both macroalgae (12.3% delay). Collectively, these embryos displayed a significant inverse logarithmic relationship between MAA concentration and percentage cleavage delay, so that the greater the MAA concentration in the eggs, the less they were affected by UV radiation. This is the first study to examine such MAA manipulation of cellular MAA concentrations with no prior UV exposure of the experimental subjects. Concentrations of MAAs were also measured in unfertilized eggs, blastulae, gastrulae and early pluteus larvae, providing the first documentation of changes in MAAs during embryological and larval development. The concentration of shinorine (the principal MAA in the eggs) did not change during short‐term UV exposure in vivo or long‐term exposure in vitro; such photostability is a useful attribute of a natural sunscreen.

Echinoderm eggs and embryos: Procurement and culture

The protocols outlined here hopefully will provide researchers with healthy, beautiful echinoderm oocytes, eggs, and embryos for experimental use. The large size of echinoderm oocytes and eggs, the ease with which they can be manipulated, and (in many species) their optical clarity, make them an ideal model system for studying not only the events specific to oocyte maturation and fertilization, but also for investigating more general questions regarding cell cycle regulation in an in vivo system. The quick rate at which development proceeds after fertilization to produce transparent embryos and larva makes the echinoderm an advantageous organism for studying deuterostome embryogenesis. Continued use of the echinoderms as model systems will undoubtedly uncover exciting answers to questions regarding fertilization, cell cycle regulation, morphogenesis, and how developmental events are controlled.

Proteomic responses of sea urchin embryos to stressful ultraviolet radiation.

Solar ultraviolet radiation (UVR, 290-400 nm) penetrates into seawater and can harm shallow-dwelling and planktonic marine organisms. Studies dating back to the 1930s revealed that echinoids, especially sea urchin embryos, are powerful models for deciphering the effects of UVR on embryonic development and how embryos defend themselves against UV-induced damage. In addition to providing a large number of synchronously developing embryos amenable to cellular, biochemical, molecular, and single-cell analyses, the purple sea urchin, Strongylocentrotus purpuratus, also offers an annotated genome. Together, these aspects allow for the in-depth study of molecular and biochemical signatures of UVR stress. Here, we review the effects of UVR on embryonic development, focusing on the early-cleavage stages, and begin to integrate data regarding single-protein responses with comprehensive proteomic assessments. Proteomic studies reveal changes in levels of post-translational modifications to proteins that respond to UVR, and identify proteins that can then be interrogated as putative targets or components of stress-response pathways. These responsive proteins are distributed among systems upon which targeted studies can now begin to be mapped. Post-transcriptional and translational controls may provide early embryos with a rapid, fine-tuned response to stress during early stages, especially during pre-blastula stages that rely primarily on maternally derived defenses rather than on responses through zygotic gene transcription.