The statocysts of cephalopods
Williamson, R. (1995). The statocysts of cephalopods, in: Abbott, N.J. et al. (Ed.) Cephalopod neurobiology: neuroscience studies in squid, octopus and cuttlefish. pp. 503-520
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| Abstract |
The statocysts of most cephalopods are sense organs of great sophistication with macula/statolith systems that respond to gravity and crista/cupula systems that operate as angular velocity transducers. These systems show strong parallels with their vertebrate counterparts in the vestibular organ of the inner ear, both in terms of their afferent response characteristics and in the mechano-electric transduction mechanism of the sensory hair cells. The cephalopod statocysts, unlike those of most other invertebrates, have both primary and secondary sensory hair cells. These hair cells have a unidirectional morphological and physiological polarization. The primary afferent neurones of the secondary sensory hair cells have their somata in the statocyst sensory epithelium. The statocyst sensory epithelia receive a very large efferent innervation from the brain that can excite or inhibit the afferent activity. These two efferent effects appear to use separate neurotransmitters, acetylcholine for the inhibition and a catecholamine for excitation. Within the central nervous system, the sensory input from the statocysts is integrated into a variety of behaviours, including locomotion, posture, control of eye movements, and control of body colour pattern. The morphological and physiological basis of these processes are beginning to be understood. The sensory solutions to the problems of balance and orientation that cephalopods and vertebrates have evolved show close parallels. It is anticipated that a comparison of these two systems will give a greater understanding of the basic mechanisms that are important for the operation of all such sensory systems. |
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