Cholinergic and aminergic nervous systems in developing cercariae and metacercariae of Diplostomum pseudospathaceum Niewiadomska, 1984 (Digenea).

Comparative studies on the cholinergic (ChNS) and aminergic (ANS) nervous systems were carried out in developing cercariae and metacercariae of Diplostomum pseudospathaceum. A method for the localization of cholinesterase and nonspecific esterase activities, and the method for the histofluorescence of biogenic amines were used. The first traces of the ChNS were found in the cercarial embryo, and during growth of the cercaria, the brain ganglia and commissure, as well as anterior and posterior nerve trunks joined by commissures, were progressively developed. The fully developed ChNS was observed in the emerged cercaria. Further development in metacercariae leads to an orthogon-like structure. Histofluorescence of catecholamines appeared in the brain ganglia and the proximal part of the ventral trunks only in young cercaria (having furcae, tail stem and body of the same size). The emerged cercaria had an ANS different from the ChNS (in part of the nervous system there was no fluorescence). The differences disappeared during the development of the metacercaria. The evolutionary and functional interpretation of the various developmental rates of the ChNS and ANS were discussed.