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(1) An auditory vesicle, the organ of equilibration in invertebrates. Statocysts are in the form of a pit or a vesicle embedded under the outer skin covering. They may also be in the form of a flask-shaped protrusion (for example, in medusae and sea urchins). A statocyst contains one or more solid formations, which are known as statoliths, or otoliths. When the body position is changed, the otoliths move, thus stimulating the sensory cells of the statocyst. The nerve impulse is transmitted from the sensory cells along the nerve fibers to the central nervous system, causing a response that leads to restoration of equilibrium.
(2) A plant cell in which tiny, mobile starch granules, known as statoliths, are formed. Statocysts are found in the rootcaps, the apices of cereal coleoptiles, and other growing parts.