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.

Hymenolepis nana: the fine structure of the adult nervous system

“…Thus, the ganglia, commissures, nerve cords and main nerve tracts in the scolex and neck region of H. nana consist of a cortex of nerve cell bodies and a core of nerve fibres as do those of invertebrates generally. The absence of a delimiting sheath or capsule around the main nervous structures is typical of cestodes (Morseth, 1967;Sakamoto & Sugimura, 1969;Webb & Davey, 1975a;Webb, 1977 ;Specian&Lumsden, 1980). Consequently, there is no clear demarcation between the nervous system and the surrounding tissues, and the nervous structures appear to be loosely embedded within them.…”

“…Surprisingly few observations have been made on the fine structure of cestode nervous tissue (Morseth, 1967;Sakamoto & Sugimura, 1969;Golubev & Kashapova, 1975;Webb & Davey, 1975aWebb, 1976Webb, , 1977Specian & Lumsden, 1980;Gustafsson & Wikgren, 1981). To date there has been no detailed study of the fine structure of the nervous system of an adult worm; the only comparable study involved the cysticercoid larva of another cyclophyllidean species, Hymenolepis microstoma (Webb, 1976;Webb & Davey, 1975a). The present investigation was undertaken to fill this gap, although it is limited to the main concentration of nervous tissue in the scolex and neck region of Hymenolepis nana.…”

The brain structure of selected trypanorhynch tapeworms

“…It has generally been assumed that with the adoption of a parasitic mode of life, the nervous system of cestodes underwent a reduction or secondary simplification; the sedentary life style of the adult cestodes does not require an elaborate or well‐organized nervous system (Beklemishev, 1964). However, detailed studies of the tapeworm histology, ultrastructure, and immunocytochemistry (Biserova, 1991, 1997; Biserova et al, 2000; Biserova, Gustafsson, Reuter, & Terenina, 1996; Coil, 1991; Fairweather & Threadgold, 1983; Gustafsson, 1984, 1990; Gustafsson & Wikgren, 1981; Halton & Gustafsson, 1996; Halton & Maule, 2004; Rees, 1946, 1961, 1966; Webb & Davey, 1975) have revealed a complex accumulation of neurons and neuropils, which correspond to the brain of bilateria according to the definition of a neuroanatomy glossary (Biserova, 2016; Richter et al, 2010). The cestode brain is located in the anterior part of the body referred to as a scolex.…”

Localization of a sodium-dependent high-affinity serotonin transporter and recruitment of exogenous serotonin by the cestodeHymenolepis diminuta: an autoradiographic and immunohistochemical study

“…Vesicles of this type were seen in nervous tissue of Hymenolepis spp. (for example, see Webb and Davey 1974), and it was deduced that they are serotonin stores in M. vogae (Terenina et al 1995). Collectively these observations suggest that in cestodes, as in other animals, serotonin is localized in dense-core vesicles.…”