Predation on scyphozoan polyps and selective nematocyst incorporation dynamics in the aeolid, Caloria militaris

Abstract

Aeolid nudibranchs are known to prey on various cnidarians and incorporate nematocysts from their prey into their cerata (dorsal appendages) for self-defense. Nematocyst incorporation is selective, and is based on species, diet, prey availability, and predation pressure. This study investigated the interactions between two nudibranch species, Caloria militaris and Flabellina affinis, and scyphozoan polyps from common eastern Mediterranean jellyfish species, including Rhopilema nomadica, Cassiopea andromeda, Phyllorhiza punctata, and Aurelia sp. Laboratory experiments were used to assess whether these nudibranchs feed on scyphozoan polyps, and if they incorporate the prey nematocysts into the cerata. Results indicate that while F. affinis avoids scyphozoan polyps, C. militaris consumes all tested species, and can subsist on them for extended durations (up to 255 days). Predation rates varied among prey species tested, ranging from a mean of 8 to 43.3 polyps day-1. However, C. militaris does not store scyphozoan nematocysts. These findings contribute to understanding nudibranch feeding ecology and the potential roles these predators play in regulating jellyfish blooms. Identification of scyphozoan nematocysts in the cerata of predator aeolid nudibranchs is discussed as a means to locate cryptic scyphozoan polyps in the marine environment.