Ambulacral system

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Water vascular system of the starfish (scheme)

The ambulacral (or water vascular system ), also called water vascular system is a typical feature for the root of echinoderms ( echinoderms , z. B. starfish and sea urchins ). It consists of a system of channels inside the animals, which is filled with a special liquid and, as a ring channel, encompasses the animal's throat, from which five radial channels arise. The name water vascular system is a bit misleading, since the liquid is not seawater, but protein-containing coelom liquid . On the outside of the animal, the ambulacral system is visible on the small tentacle-like feet.

The ambulacral system is a hydraulic system . With the help of the liquid and small, muscular ampoules inside, the echinodermates are able to move their little feet in a targeted manner. For a long time, suction cups on the feet of starfish and other Echinodermata were suspected to be the primary adhesion mechanisms. However, recent studies show that adhesion to the substrate is most likely exclusively via the secretion of an adhesive material.

Functioning of an ambulacral foot with an associated ampoule

Another component of the ambulacral system is the madrepora plate (also called sieve plate), which is clearly visible on the top of starfish and sea urchins. This small, porous structure serves to equalize pressure. An exchange of sea water takes place via the pore openings of the Madreporenplatte.

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  Close-up of the Madreporenplatte (sieve plate)

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  Beach sea ​​urchins ( Psammechinus miliaris ) - the ambulacral feet that are pushed out far over the spines are easily recognizable

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  Starfish, underside (Asteroidea)

Individual evidence

1. ^ D Nichols: Functional morphology of the water vascular system. In: Physiology of echinodermata (ed. RA Boolootian), Interscience Publishers, New York 1966, pp. 219-244.
2. ^ Elise Hennebert: Adhesion Mechanisms Developed by Sea Stars: A Review of the Ultrastructure and Composition of Tube Feet and Their Secretion. in Biological Adhesive Systems (ed. Janey v. Byern and Ingo Grunwald), Springer Vienna 2010, p. 99.
3. ^ John C. Ferguson: Rate of Water Admission Through the Madreporite of a Starfish. Journal of Experimental Biology 1989, vol. 145 pp. 147-156.