Catecholaminergic and peptidergic nervous systems of a mermithid nematode, Romanomermis culicivorax, Ross and Smith, 1976

Jagdale, Ganpati Baburao (1993) Catecholaminergic and peptidergic nervous systems of a mermithid nematode, Romanomermis culicivorax, Ross and Smith, 1976. Masters thesis, Memorial University of Newfoundland.

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Abstract

The nervous system of the mermithid nematode, Romanomermis culicivorax, was investigated at different developmental stages for the distribution of catecholamine(s) and the neuropeptide FMRF-amide. A glyoxylic acid-induced fluorescence method was used to locate catecholamines, while FMRF-amide was detected by immunohistochemistry. -- The distribution of sense organs was elucidated by scanning electron microscope studies. Six cephalic sensory papillae (two lateral, two dorso-lateral and two ventro-lateral) and two amphids were found in the head tips of adult nematodes. In males, each lateral papilla contained two pores and each of the dorso-lateral and ventro-lateral cephalic papillae contained three pores. Three pores were present in each of the six cephalic papillae of females. Several caudal sensory papillae were present in the tails of males, each of which contained one pore. Caudal sensory papillae were absent in the tail of females. -- The catecholaminergic and peptidergic nervous systems increased in complexity during development. In the adult nematode, catecholamine(s) occurred in the nerve ring, ganglia of the nerve ring, cephalic nerves, ventral and dorsal nerve cords and mid-body region ganglia. The distribution of catecholaminergic ganglia in the tail region was different for each sex. The tail region of males contained 16-20 catecholaminergic ganglia, whereas the tail of females contained only two ganglia. The catecholamine widely distributed throughout the nervous system of R. culicivorax is not dopamine, since immunoreactivity to dopamine was observed only in the amphids. -- The role of the catecholamine(s) in reproduction was studied by measuring the fluorescence intensity of catecholamine(s) in the nervous systems of males and females under different rearing conditions. A significantly greater concentration of catecholamine was recorded in the nervous system of adult males and females than in post-parasitic juveniles. A significantly higher concentration of catecholamines was observed in adults that were reared in physical contact with the opposite sex than in those reared in isolation. Adult males that were reared with females in the same water rearing medium, but physically separated by a barrier, displayed a significantly greater concentration of catecholamines in their nervous systems than did males reared in isolation, but the catecholamine staining intensity of such males was less than in males that were allowed physical contact with females. In adult males, the fluorescence intensity of catecholamines declined progressively during and after copulation. However, in adult females, the intensity of catecholamines remained constant before, during and after copulation. It is suggested that the catecholamine(s) may play a role in regulating copulatory behaviour, egg production and/or oviposition. -- In adults, FMRF-amide-like peptide was present in the nerve ring, cephalic papillary ganglia, cephalic nerves, amphids, ganglia posterior to the nerve ring, longitudinal nerve cords and several mid-body region ganglia. The distribution of peptidergic ganglia in the tail region was different for each sex. Four clusters of ganglia were present in the tail of females, whereas such ganglia were absent in the tail of males. -- The results suggest that catecholamines and FMRF amide like peptides are widely distributed within the nervous system of R. culicivorax. These substances might function as neurohormones and neurotransmitters in controlling physiological and developmental processes.

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