Crabs have angular acceleration detectors similar in size and construction to the analogous vertebrate semicircular canals. They have a row of slender thread instead of a gelatinous cupula embedded on a bed of hair cells. These thread hairs are hinged to their bases on one side and linked via a cuticular rod or chorda to two bipolar sensory neurones contained in a specialized chordotonal organ. Linear accelerations affect the angular acceleration receptors in crabs as in vertebrates, so tilt in a gravitational field influences resting nerve spike frequencies and the relative sensitivity of different directional classes of angular acceleration afferents. A recent discovery is that the angular acceleration afferents in crabs are modulated by small changes in hydrostatic pressure allowing these organs to function as depth receptors. Using a comparative approach, this discovery prompted a similar finding for the isolated semicircular canal system of a shark. Crabs also have a brain with a small number of large identified cells. A small set of equilibrium interneurones with direct input from the statocyst are known and their activity under gravity may be sampled using implanted Teflon coated electrodes for long periods including during oscillation and freefall in Parabolic flight.
|Number of pages||1|
|Journal||The Journal of Physiological Sciences|
|Issue number||Suppl. 1|
|Publication status||Published - 2009|