Luidia magellanica is a large and aggressive specialist predator of other
echinoderms. Its diet includes
brittle stars such as
Ophiactis,
sea urchins such as
Tetrapygus niger and starfish such as
Patiria. In the subtidal zone of temperate Chile it feeds on eight different species of echinoderm, and with
Meyenaster gelatinosus is the dominant predator. Many of the starfish in this zone have missing or regenerating arms, and this is likely to be as a result of a near-lethal encounter with either
L. magellanica or
M. gelatinosus. Both of these species also exhibit
cannibalism. When attacked by
M. gelatinosus or by a larger member of its own species,
L. magellanica tends to
autotomise some of a single arm. In a study off the coast of Chile, between 50 and 70% of individual
L. magellanica were found to have regenerating arms. Other species of starfish recorded in the same zone in the cold waters off Peru are
Patiria chilensis,
Stichaster striatus and
Meyenaster gelatinosus.
L. magellanica plays an important role in the control of grazing echinoids, and such factors as
El Niño events can alter the population dynamics. If fewer
L. magellanica are recruited because of temperature and other factors, more grazers such as
Tetrapygus niger survive, and barren areas occur. Alternatively, when more of the starfish are present, fewer grazers cause less damage and the kelp flourishes unchecked. ==References==