each brittle star can produce 15 new individuals during the course of a year. Life span Brittle stars generally sexually mature in two to three years, become full grown in three to four years, and live up to five years. Members of Euryalina, such as Gorgonocephalus, may live much longer. Regeneration Ophiuroids can readily regenerate lost arms or arm segments unless all arms are lost. Ophiuroids use this ability to escape predators, in a way similar to lizards which deliberately shed the distal part of their tails to confuse pursuers. Moreover, the Amphiuridae can regenerate gut and gonad fragments lost along with the arms. Discarded arms have not been shown to have the ability to regenerate. Locomotion Brittle stars use their arms for locomotion. Brittle stars move fairly rapidly by wriggling their arms which are highly flexible and enable the animals to make either snake-like or rowing movements. However, they tend to attach themselves to the sea floor or to sponges or cnidarians, such as coral. They move as if they were bilaterally symmetrical, with an arbitrary leg selected as the symmetry axis and the other four used in propulsion. The axial leg may be facing or trailing the direction of motion, and due to the radially symmetrical nervous system, can be changed whenever a change in direction is necessary. Bioluminescence Over 60 species of brittle stars are known to be bioluminescent. Most of these produce light in the green wavelengths, although a few blue-emitting species have also been discovered. Both shallow-water and deep-sea species of brittle stars are known to produce light. Presumably, this light is used to deter predators. Ecology Brittle stars live in areas from the low-tide level downwards. Six families live at least 2 m deep; the genera Ophiura, Amphiophiura, and Ophiacantha range below 4 m. Shallow species live among sponges, stones, or coral, or under the sand or mud, with only their arms protruding. Two of the best-known shallow species are the green brittle star (Ophioderma brevispina), found from Massachusetts to Brazil, and the common European brittle star (Ophiothrix fragilis). Deep-water species tend to live in or on the sea floor or adhere to coral, urchins, or xenophyophores. The most widespread species is the long-armed brittle star (Amphipholis squamata), a grayish or bluish, strongly luminescent species. Parasites The main parasite to enter the digestive tract or genitals are protozoans. Crustaceans, nematodes, trematodes, and polychaete annelids