Echinoderms are usually intricate parts of their ecosystems. Many asteroids are keystone species. Sea urchins, if not controlled by predators, may overgraze their habitat. Asteroids have several commensals, including polychaetes that feed on leftovers from the sea star's prey items.
Echinoderms in general are most vulnerable in their larval stage. As adults, asteroids have an anti-predator adaptation where they can lose an arm to a predator and the arm is later regenerated. Holothurians discharge sticky tubules, known as Cuvierian tubules , at a potential predator. Otters prey mainly on sea urchins.
Echinodermata is prey of: Pycnopodia Merluccius bilinearis Urophycis tenuis Gadidae Melanogrammus aeglefinus Hemitripterus americanus Myoxocephalus octodecemspinosus Leucoraja erinacea Leucoraja ocellata Amblyraja radiata Macrozoarces americanus Anarhichas Tautogolabrus adspersus Pleuronectes americanus Hippoglossoides platessoides Mustelus canis Lophius americanus Caretta caretta Corvus caurinus Enhydra lutris
Based on studies in: USA: Washington, Cape Flattery (Littoral, Rocky shore) USA, Northeastern US contintental shelf (Coastal)
This list may not be complete but is based on published studies.
R. T. Paine, Food webs: linkage, interaction strength and community infrastructure, J. Anim. Ecol. 49:667-685, from p. 670 (1980).
Link J (2002) Does food web theory work for marine ecosystems? Mar Ecol Prog Ser 230:19
Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org
The non-centralized nervous system allows echinoderms to sense their environment from all sides. Adult pheromones may attract larvae, which tend to settle near conspecific adults. Metamorphosis in some species is triggered by adult pheromones.
Echinoderms are deuterostomes. The larvae, which are planktotrophic or lecithotrophic, have 3-part paired coeloms. Embryonic coelomic structures have specific fates as the bilaterally symmetrical larvae metamorphose into radially symmetric adults. Adult pheromones may attract larvae, which tend to settle near conspecific adults. Metamorphosis in some species is triggered by adult pheromones.
Echinoderms are mainly gonochoristic (having separate sexes), with exceptions among the asteroids, holothurians and ophuroids. Holothurians possess a single gonad, crinoids lack distinct gonads, while asteroids and echinoids have multiple gonads. Echinoderm reproductive strategies vary from free spawning and indirect development to brooding and direct development. Spawning is probably a noctural event.
Parental investment ranges from no care after the release of eggs for free spawning to brooding the young. Brooding is found in polar and boreal echinoderms and some deep sea echinoderms, where environments are more difficult for the larvae.
"Their [echinoderms'] bodies work by unique exploitation of hydrostatic principles. Feet, each a thin tube ending in a sucker and kept firm by the pressure of water within, wave and curl in rows along the arms. The water for this system circulates quite separately from that in the body cavity. It is drawn through a pore into a channel surrounding the mouth and circulated throughout the body and into the myriads of tube feet. When a drifting particle of food touches an arm, tube feet fasten on to it and pass it on from one to another until it reaches the gutter that runs down the upper surface of the arm to the mouth at the centre." (Attenborough 1979:49) Learn more about this functional adaptation.
Attenborough, David. 1979. Life on Earth. Boston, MA: Little, Brown and Company. 319 p.