Meeting Abstract
Essentially all surfaces of marine plants and animals host epibionts. Epibionts may harm their hosts in a number of ways, including impeding gas exchange or increasing the costs of locomotion. Epibionts can also be beneficial. For example, epibionts may camouflage their hosts, and photosynthetic epibionts can produce oxygen. In general, the costs of epibionts appear to vastly outweigh their benefits. Many organisms, therefore, shed epibionts by grooming or molting or keep them from attaching initially by using surface waxes and cuticular structures. In this study, we examined how epibionts affect local oxygen supply to temperate and Antarctic species of pycnogonids (sea spiders). We also tested the effectiveness of different methods that pycnogonids use to control epibionts (grooming, cuticle wettability, and cuticular waxes). In two temperate species, epibionts consisted primarily of algae and diatoms, formed layers approximately 0.25 mm thick and colonized at least 75% of available surface area. We used microelectrodes to measure oxygen levels in and under the layers of epibionts. In bright light, the epibionts produced high levels of oxygen. In the dark, the epibionts had no negative effect on local oxygen supply. We tested mechanisms of epibiont control by pycnogonids in three ways: disabling their ovigers to prevent grooming, extracting wax layers from their cuticle, and measuring the wettability of their cuticle; however, none of these mechanisms decreased epibiont coverage. These findings indicate that in temperate environments, pycnogonid epibionts are not costly and, in some circumstances, may be beneficial. We will carry out parallel tests on much larger Antarctic species around McMurdo station in the fall of 2015. NSF PLR- 1341485.
