Aspects Of The Oculomotor System Of Callinectes Sapidus

An isolated perfused preparation was developed for the study of several aspects of the oculomotor system of the blue crab, Callinectes sapidus. The system for eyestalk rotation was investigated on an extracellular level. Two antagonistic pairs of muscles under visual and statocyst control were found to be responsible for stabilization and rotation of the eyestalk. The primary sensory input to the muscles appears to be from the statocysts, with both static position sense and dynamic acceleration components influencing the motor response. Two sensory feedback systems from mechanoreceptive hairs were found which influence the response of the eye stalks to statocyst input. The function of one system appears to be to allow· the animal to differentiate between statocyst stimulation caused by whole body movement and that caused by movement of the basal segment of the antennule in which the statocyst is lodged. The second negative feedback system appears to have a multiple function. It is believed to function to null out the tonic excitatory position sense input from the statocysts when it is necessary for the eye to make a movement which is contrary to the position sense input as, for example, when the animal is following a visual target whose direction is opposite to that of the statocyst drive. It also produces reciprocal inhibition of the antagonist muscle. In addition, this system may be responsible for the incomplete compensation seen in compensatory eye movements made in response to pitch of the body. A preliminary survey of the oculomotor neurons and interneurons in the cerebral ganglion established the potential of this ganglion for intracellular recording from components of the oculomotor system. Recordings were made from both motorneurons and interneurons. The recording from interneurone of the oculomotor system was particularly good. Eye movements could be elicted in response to visual and tactile stimuli while recording from the ganglion. The preparation appears ·to be an excellent system in which to undertake an extensive analysis of intracellular events in the neuronal network underlying stereotyped eye movements and could lead to an understanding of the neuronal basis for such movements. In the course of the above work on the oculomotor system, same observations were made on the cor frontale which controls the blood pressure to the cerebral system. The cor frontale had been thought to function as a heart regulating blood flow to the cerebral ganglion. It appears from this work that the cor frontale may not function as a heart but rather as a resistive mechanism for regulation of the blood pressure, more like the vertebrate arteriole. Furthermore, the function of this organ may not be to protect the flow to the cerebral ganglion but rather to insure the constancy of the pressure in the peripheral sensory, integrative and oculomotor apparatus of the eyecup