Effects of capture surface morphology on feeding success of scyphomedusae : a comparative study

Abstract

Predation by feeding-current foraging medusae can have detrimental effects on prey populations. Understanding the mechanics that control prey selection and ingestion rates with different types of prey enables us to better predict the predatory impact of these medusae. We quantified the outcomes of each post-entrainment stage of the feeding process in multiple scyphozoan jellyfish species to understand how post-entrainment feeding events influence feeding patterns. Using 3-dimensional video, we observed and quantified the fate of both passive and actively swimming prey that were entrained in the feeding current of 5 different scyphomedusan species belonging to the orders Semaeostomeae and Rhizostomeae. Less than 65% of entrained prey contacted the capture surfaces (termed contact efficiency) of the semaeostome medusae, while the rhizostome medusae came into contact with less than 35% of the prey entrained in the feeding current. However, when contacted, prey were very likely to be ingested (>90%) by all species examined. These results suggest that prey capture by oblate medusae appears to be largely limited by the probability that prey entrained in the feeding current will contact a capture surface. As a passive process, this contact stage of the feeding process is directly affected by the morphology of the contact surfaces. The importance of the contact stage of the feeding process suggests that differences in prey selection patterns observed among oblate medusan taxa are likely dominated by the morphology of contact surfaces as opposed to traits which influence the other stages of the feeding process, i.e. bell shape and nematocysts.