Jellyfish: Scyphozoa

Physical characteristics: The swimming bell of sea nettles can reach 10 inches (25 centimeters) in diameter, but most sea nettles are much smaller. The edges of the swimming bell are petal shaped. One large tentacle emerges from between the petals, and twice as many small tentacles arise from beneath the petals. Eight sense structures are present in alternate spaces between the petals. The narrow oral arms are long and filmy. The colors of medusae range from milky white to white with radiating purplish red stripes on the bell.

Geographic range: Sea nettles live on both sides of the Atlantic Ocean, in the Indian Ocean, and in the eastern part of the Pacific Ocean.

Habitat: Sea nettle medusae live in estuaries (EHS-chew-AIR-eez), the areas where rivers meet the sea.

Diet: Sea nettle medusae eat small crustaceans, comb jellies, and fish eggs and larvae. The polyps eat oyster larvae.

The edges of the swimming bell of sea nettles are petal shaped. (© Gregory G. Dimijian/Photo Researchers, Inc.)

Behavior and reproduction: Sea nettle medusae swim constantly in slow circles. They feed continuously. The life cycle of sea nettles has both a polyp and a medusa stage. The release of eggs and sperm takes place around dawn.

Sea nettles and people: Sea nettles have an irritating sting.

Conservation status: Sea nettles are not threatened or endangered. ∎