Statocyst

The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves,[1] cnidarians,[2] ctenophorans,[3] echinoderms,[4] cephalopods,[5][6] crustaceans,[7] and gastropods,[8] A similar structure is also found in Xenoturbella.

[9] The statocyst consists of a sac-like structure containing a mineralised mass (statolith) and numerous innervated sensory hairs (setae).

Deflection of setae by the statolith in response to gravity activates neurons, providing feedback to the animal on change in orientation and allowing balance to be maintained.

[citation needed] In cephalopods like squids, statocysts provide a cochlea-like mechanism to hear.

[10][11] As a result, the longfin inshore squid for instance can hear low-frequency sounds between 30 and 500 Hz when the water temperature is above 8 °C (46 °F).