MEPS 568:101-110 (2017)  -  DOI: https://doi.org/10.3354/meps12059

ABSTRACT: Understanding the factors that control predation in pelagic communities can inform predictions of community structure in marine ecosystems. Ubiquitous and selective predators such as cnidarian hydromedusae rely on their nematocysts to capture and retain prey but it is not clear how the density and spatial distribution of these cells relate to predation mode. We examined the relationship between prey capture and nematocyst distribution in the tentacles of Aglantha digitale and Proboscidactyla flavicirrata, which are considered ambush predators, and Clytia gregaria and Mitrocoma cellularia, which are considered feeding-current predators. First, we analyzed video of predator-prey interactions to compare capture locations of Artemia nauplii relative to the bell margin of each species. Second, tentacles of the same 4 species plus Sarsia tubulosa and Aequorea victoria were analyzed using microscopy to determine nematocyst distribution along their lengths. By analyzing behavior and morphology simultaneously, we found that the ambush predators A. digitale and P. flavicirrata have higher nematocyst density far from the bell and tend to capture more prey in the same region. In contrast, the feeding-current predators C. gregaria and M. cellularia capture most of their prey close to the bell, where they also show a slight increase in nematocyst densities. The presence of high nematocyst densities in regions where prey are likely to contact feeding structures serves to increase capture efficiencies. Quantifying the relationship between prey capture and nematocyst locations for different foraging strategies will strengthen the ability of researchers to predict feeding behavior based on morphological features.

KEY WORDS: Feeding behavior · Functional morphology · Predation · Zooplankton · Aequorea victoria · Aglantha digitale · Clytia gregaria · Mitrocoma cellularia · Proboscidactyla flavicirrata · Sarsia tubulosa