The gross anatomy and histology of the nervous system of the metacestode of Hymenolepis microstoma

Abstract

The central nervous system of the metacestode of Hymenolepis microstoma consists of three levels of ganglia. The bilateral cerebral ganglia, joined by a broad transverse commissure, are situated posteriad to the outer rostellar capsule. The bilateral rostellar ganglia, joined by a medial transverse commissure and a dorsal and a ventral circular commissure, are situated between the inner and outer rostellar capsules. The single rostral ganglion is found within the inner rostellar capsule. Numerous nerves and connectives are given off from the various ganglia; the nerves innervate the tissues and organs of the scolex and presumptive neck of the metacestode. Histologically, the ganglia and large commissures consist of a rind of nerve cell bodies surrounding a compact core of neuropile. A delimiting sheath or capsule is not present. Glial tissue is absent. Muscle cells, tegumental cells, and flame cells may interdigitate with the nerve cells. The nerve cell bodies give off numerous neurites that pursue a tortuous course through the neuropile.