#phylliroe

Phylliroe is a genus of nudibranch that actually swims to catch its prey: jellyfish-like hydromedusae. It grows 5cm long, and different species are found in the tropical Atlantic and Pacific oceans, and the Mediterranean sea. If you think it looks like a fish, you're not alone; this nudibranch is considered an example of convergent evolution, evolving similar swimming mechanisms to fish - which you can watch in this video. One more quirk of this genus: it glows (bioluminesces)!

Phylliroe sp. (P. atlantica & P. bucephalum)

Taxonomy: Animalia, Mollusca, Gastropoda, Nudibranchia, Dendronotida, Tritonioidea, Phylliroidae, Phylliroe, Phylliroe sp.

Description: Phylliroe are laterally compressed nudibranchs, with prominent rhinophores and transparent bodies. They posess bioluminescent markings on their bodies. The lateral compression, whisker-like rhinophores and formation of a tail like structure gives these nudibranchs the appearance of a fish, which makes them iconic amongst other nudibranch species.

Lifestyle: Phylliroe live in the Atlantic, Pacific, and Medeterranean: P. atlantica in the first two and P. bucephalum in the latter. These nudibranchs live in deep water, hence the unusual presence of bioluminescence. Both species have a parasitic life cycle; the larval forms attach themselves to the bells of Zanclea costata with their foot, where they feed on the tissues of the bell. As the nudibranch reaches its maximum size of 550mm, the jellyfish shrinks in size, resulting in the adult nudibranch outgrowing the jellyfish after 10 days. Phylliroe then eats the tentacles of the host and departs to live independently. Much of the remaining life cycle of this genus is unknown.

Images from seaslugs, Fabien Michenet and sea slugs of Hawai’i