Thimble jellyfish Thimble jellyfish The thimble jellyfish ("Linuche unguiculata") is a species of cnidarian found in the neotropical Atlantic Ocean. It is a tiny jellyfish with a straight-sided, flat-topped bell. This jellyfish is the most common cause of seabather's eruption, a reaction caused by the injection of juvenile jellyfish nematocysts into human skin. The medusa of the thimble jellyfish has straight sides with sixteen grooves, and a flat top. The coronal groove between the top and sides provides flexibility. The margin of the bell has sixteen lappets (folds), the niches between these bearing alternately rhopalia (sense organs) and short tentacles (eight of
Jellyfish the presence of a named and cited example indicates that at least that species within its group has been called a jellyfish. The subphylum Medusozoa includes all cnidarians with a medusa stage in their life cycle. The basic cycle is egg, planula larva, polyp, medusa, with the medusa being the sexual stage. The polyp stage is sometimes secondarily lost. The subphylum include the major taxa, Scyphozoa (large jellyfish), Cubozoa (box jellyfish) and Hydrozoa (small jellyfish), and excludes Anthozoa (corals and sea anemones). This suggests that the medusa form evolved after the polyps. Medusozoans have tetramerous symmetry, with parts in fours