Helmet jellyfish
| Helmet jellyfish | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Cnidaria |
| Class: | Scyphozoa |
| Order: | Coronatae |
| Family: | Periphyllidae |
| Genus: | Periphylla F. Müller, 1861 |
| Species: | P. periphylla
|
| Binomial name | |
| Periphylla periphylla | |
| Synonyms | |
| |
The helmet jellyfish (Periphylla periphylla), sometimes called the merchant-cap, is a luminescent, red-colored jellyfish of the deep sea, belonging to the order Coronatae of the phylum Cnidaria. It is the only species in the monotypic genus Periphylla and a rare example of a scyphozoan with a polyp-less life cycle, occurring exclusively as a medusa.
Periphylla is intensely photophobic, and thus only seldom leaves the bathypelagic zone (likely only on particularly dark nights).