Rotationssinn nach dem Bogengangsprinzip bei Crustaceen

Summary

Blinded crabs (Carcinus maenas andMaja verrucosa) show compensatory eye stalk movements on rotation about a vertical axis, in water and in air. On a sudden arrest of the turntable typical after-effects are observed, which show a striking resemblance to those known from vertebrates. All these reactions are abolished after bilateral elimination of the so-called thread hairs within the statocysts (experiments onMaja). In fresh preparations these hairs can be seen to follow the slightest movements of the surrounding fluid, swaying around their point of attachment.

Elimination of the thread hairs does not diminish, but does markedly delay the compensatory eye stalk movements of a blinded crab on rotation about horizontal axes. The latter reactions are abolished if in addition the hook hairs (i.e. the sense hairs of the statolith-bearing type) are destroyed.

It is concluded that the statocyst of crabs is a staticdynamic sense organ: the hook hairs are position receptors, the thread hairs react to angular displacements about all three main body axes; the group hairs may have no sensory function at all.

Rotation sense may be expected to occur in other Crustacea possessing thread hairs or similar receptors in their statocysts as well.