GROSS-ANATOMY OF THE MUSCLE SYSTEMS OF FASCIOLA-HEPATICA AS VISUALIZED BY PHALLOIDIN-FLUORESCENCE AND CONFOCAL MICROSCOPY

Neuropeptides, biogenic amines and acetylcholine are expressed abundan tly within the nervous systems of parasitic flatworms, and are particu larly evident in the innervation of the musculature. Such associations have implicated the nervous system in locomotion, host attachment and reproductive co-ordination. Information on the muscle systems of para sitic flatworms is generally sparse, in particular those muscles assoc iated with the reproductive system, intestinal tract and attachment ap paratus. Also, the use of sectioned material has left description of t he 3-dimensional organization of the musculature largely unrecorded. U sing fluorescein isothiocyanate (FITC)-labelled phalloidin as a site-s pecific probe for filamentous actin, applied to whole-mount preparatio ns of adult Fasciola hepatica and examined by confocal scanning laser microscopy, the present work reports on the organization of the major muscle systems in this trematode parasite. A highly regular array of o uter circular, intermediate longitudinal and inner diagonal fibres dis tinguishes the body wall musculature, which is also involved in the de velopment of both ventral and oral suckers. Circular fibres dominate t he duct walls of the male and female reproductive systems, whereas the muscles of the intestinal tract have a somewhat diffuse arrangement o f fibres. An understanding of the structural complexity of the muscle systems of parasitic flatworms is considered as fundamental to the int erpretation of results from physiological experiments.