Sea Walnut

Mnemiopsis have a lobed body that is oval-shaped and transparent, with four rows of ciliated combs that run along the body vertically and glow blue-green when disturbed. They have several feeding tentacles. Unlike cnidarians, Mnemiopsis doesn't sting. Their body contains 97% water. They are small organisms, having a maximum body length of roughly 7–12 centimetres (3–5 in) and a diameter of 2.5 centimetres (1 in).

It is euryoecious, tolerating a wide range of salinity (2 to 38 psu), temperature (2–32 °C or 36–90 °F), and water quality.

Mnemiopsis is a carnivore that consumes zooplankton including crustaceans,[3] other comb jellies, and eggs and larvae of fish; it is sometimes known to eat smaller individuals of its own kind. It also has several other predators. Many are vertebrates, including species of birds and fish. Some predators include other members of gelatinous zooplankton such as Beroe ctenophores and various Scyphozoa (jellyfish).

This comb jelly has the capacity for self-fertilization, as they are hermaphroditic. They have gonads that contain the ovary and spermatophore bunches in their gastrodermis. This animal carries 150 eggs along each meridional canal. Eggs and sperm are released into the water column where external fertilization takes place. The spawning commences at late evening or at 1:00 or 2:00 a.m. The spawning eggs develop a thick outer layer within 1 minute after touching the seawater. As many as 10,000 eggs can be produced from large specimens in areas with good prey abundance. Egg production can start when the animals reach about 15 mm in length. Egg production increases with ctenophore size, and it is unclear when senescence occurs.

The species is blind, has no brain and moves so slowly that it is referred to as "sea walnut".
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