New data on the nervous system of Cercaria parvicaudata Stunkard & Shaw, 1931 (Trematoda: Renicolidae): revisiting old hypotheses.

Data on the interposition of the immunoreactive nerve cords in Cercaria parvicaudata Stunkard & Shaw, 1931 (Trematoda: Renicolidae) and its chaetotaxy were obtained. The nervous system of C. parvicaudata was described using immunostaining of 5-hydroxytryptamine and FMRFamide immunoreactive nerve elements. The morphology and distribution of sensory receptors were analysed using scanning electron microscopy and the silver nitrate impregnation technique. Our integrated approach to the study of the nervous system revealed a clear colocalization of surface papillae with nerve cords and commissures in C. parvicaudata. The structure of the nervous system in C. parvicaudata differs partly from the classical model that defines the entire nomenclature of chaetotaxy.