Using the filamentous actin marker, FITC-conjugated phalloidin, the major muscle systems of adult male and female
schistosomes have been examined. The body wall musculature comprises an outer sheath of circular fibres, within which
there is a compact layer of short, spindle-shaped longitudinal fibres and a lattice-like arrangement of inner diagonal fibres.
Within the oral sucker and acetabulum 3 fibre types, circular, radial and longitudinal can be distinguished. The wall of
the oesophagus is lined by a grid-like array of circular and longitudinal fibres, whereas the walls of the intestinal caeca
contain only comparably broad circular fibres. Within the female reproductive system, only circular fibres are present in
the oviduct, vitelline duct and uterus. In contrast, the wall of the ootype displays closely arranged circular and longitudinal
muscle fibres. Antisera to previously identified myoactive compounds (serotonin [5-hydroxytryptamine, 5-HT], neuropeptide
F [Moniezia expansa] and GYIRFamide [Bdelloura candida, Dugesia tigrina]) were used as neuronal markers in
a preliminary study of the spatial inter-relationships of specific nerve fibres and various muscle systems. Serotoninergic
fibres innervate both suckers and also constitute a subtegumental nerve net. In males they provide innervation to the
dorso-ventral muscle fibres of the gynaecophoric canal, and in females they innervate the circular and longitudinal muscle
fibres of the ootype. Neuropeptide F and the FMRFamide-related peptide, GYIRFamide are both localized within nerve
plexuses associated with the dorso-ventral fibres of the gynaecophoric canal, and are evident in the innervation of the
ventral and oral sucker.