The CNS (including the circumesophageal
ganglion complex and the pair of buccal ganglia) and peripheral tissue pieces (head region with tentacles and lips, lateral foot, heart, and salivary gland) were quickly dissected from older juveniles and adult snails, pinned out in Sylgardcoated petri dishes, and then covered with fixative.
The overlying connective tissue was carefully dissected to expose the circumesophageal
ganglia, specifically the supraesophageal ganglion, and the Petri dish holding the preparation was moved to a second plastic chamber (filled with FSW) mounted under a dissecting microscope.
Five photoreceptors, subdivided into types A and B, are located around the eye in the circumesophageal
nervous system in the body cavity just beneath a tentacle in Hermissenda (Stensaas et al., 1969).
Lesioning the circumesophageal
connectives, including the cheliceral ganglion, did not block the efferent activity, nor did lesions of the protocerebrum posterior to the central body and of the dorsal portion (~10%) of the central body.
Cellular distributions and functions of histamine, octopamine, and serotonin in the peripheral visual system, brain, and circumesophageal
ring of the horseshoe crab, Limulus polyphemus.
The CNS consists of a cerebral ganglion, or "brain," linked by paired circumesophageal connectives to a posterior ganglion.
Neurites from surrounding somata project into the median protocerebral neuropils [ILLUSTRATION FOR FIGURES 3B, C OMITTED] and longitudinal fibers that extend from the posterior regions of these neuropils contribute to the circumesophageal connectives [ILLUSTRATION FOR FIGURE 5 OMITTED].
Posterior projections from the median protocerebral neuropils contribute to the circumesophageal connectives and travel in bundles distinct from those associated with the median protocerebral neuropil [ILLUSTRATION FOR FIGURE 5 OMITTED].
There is no trace of a sub-esophageal ganglion; the circumesophageal connectives join a ventral ganglionic mass that is sometimes referred to as the thoracic ganglion.
Occasionally, prominent beaded axons originating from the supra-esophageal ganglion were seen in the circumesophageal connectives [ILLUSTRATION FOR FIGURE