Meeting Abstract
Desiccation is a potential problem for all life stages of intertidal animals, particularly early stages that are not capable of moving around a habitat. A common benthic reproductive strategy is to encase eggs in gelatinous masses during development. Because egg masses vary hugely in shape, size, and attachment method, they vary in desiccation resistance. The opisthobranch gastropod Haminoea vesicula attaches its flat, ribbon-shaped egg masses to a variety of benthic substrata. In False Bay, San Juan Island, Washington, USA, H. vesicula has a behavioral adaptation to prevent benthic egg masses from desiccation: adults preferentially lay egg masses on seagrass or other substrata in tide pools. However, individual masses and clumps of masses can detach and drift due to current movements. In False Bay, the worst-case scenario for desiccation involves a single egg ribbon stranded on a dry sand bar between tide pools, where it is exposed to full sun and wind for the duration of low tide (approximately 6 hours, maximum sediment temperature of 35°C in summer). Regardless of location, the egg mass will eventually be rehydrated by the incoming tide. I deployed egg masses of different ages under these field conditions. After rehydration, older embryos (spinning stages) showed higher rates of survival than newly-laid embryos (<24 hours old), but for both stages the survival rates were frequently over 25%. In the laboratory, up to 25% of embryos survived in egg masses that had lost approximately 70% of their weight after desiccation under lamps. Although many surviving embryos in both experiments appeared unhealthy, these data show that egg mass stranding is not necessarily fatal to embryos. The embryos may be able to survive a far greater range of conditions than they normally encounter, compensating for their lack of ability to move.
