Meeting Abstract

33.1  Jan. 5  Does spawning behaviour minimize exposure to environmental stressors for encapsulated embryos on rocky shores? PRZESLAWSKI, Rachel A; Stony Brook University rachel@bio.life.sunysb.edu

Organisms in intertidal environments are often exposed to a range of potential stressors. Whereas adults are able to seek shelter to avoid stress associated with low tides, embryos within egg masses are effectively sessile for the duration of their encapsulation. Here, I surveyed molluscan egg masses on two rocky shores in SE Australia over two years to test the hypothesis that eggs are deposited in order to minimize exposure to environmental stress. I predicted that egg masses are predominantly deposited in shaded habitats not prone to environmental extremes. Furthermore, I anticipated that egg masses deposited in habitats exposed to UVR, desiccation, and/or extremes in temperature and salinity will occur less frequently in these habitats during seasons of high environmental stress. Egg masses from 34 taxa were unambiguously identified, and only four of these spawned on rock platforms in full sun (Bembicium nanum, Nerita atramentosa, Siphonaria zelandica and S. denticulata). As anticipated, summer had the highest UVR index, water temperature, and air temperature as well as the lowest daytime tides. Univariate and multivariate analyses confirm that egg mass abundance was highest during this season with no change in egg mass size. Therefore, those species spawning on the upper surfaces of rocky reefs do not modify their spawning behaviour to confer protection to their encapsulated offspring by avoidance of physiologically stressful conditions, particularly UVR. Reasons for this potentially risky spawning behaviour may include food availability, juvenile or adult welfare, or response to predation.