4.2 Wednesday, Jan. 4 Gases for the masses: ecological interactions promote rapid embryonic development of a marine gastropod MORAN, AL*; PHILLIPS, NE; Clemson University, SC; Victoria University of Wellingon, NZ email@example.com
Oxygen is a limiting resource to embryos developing in protected environments. Among marine invertebrates, embryos of many taxa are enclosed in egg capsules or masses. While these provide physical protection, they also result in hypoxia-driven developmental stasis or even embryonic death when egg masses are too large, embryos are densely packed, or metabolic demand is high. The intertidal pulmonate limpet Siphonaria australis lays large, gelatinous egg masses that experience high embryo mortality from UV, desiccation, and temperature stress in nature, suggesting rapid development is advantageous. We first demonstrated that O2 levels varied from hypoxic to >2x saturation in tide pools containing Siphonaria egg masses, and that central O2 concentrations in masses also varied from zero to hyperoxic. To isolate the role that tide pool photosynthesizers (macroalgae) played in egg mass O2 dynamics and embryonic development, we kept masses in the lab on a natural light/dark cycle both with and without algae throughout development and monitored external O2, O2 in the center of masses, and development. As in tide pools, the presence of algae in lab dishes raised external O2 to >2x saturation under lighted conditions and lowered O2 to below saturation in the dark. Egg mass centers contained measurable O2 only under lighted conditions with algae, and when masses were very young. Masses kept with algae throughout development had significantly less asynchrony in development and had a higher percentage of hatching-stage embryos than masses kept without algae, suggesting that fitness of S. australis parents is likely to be higher when masses are laid in pools with abundant O2 production from macroalgae.