Fine structure of the nervous system and specialized nerve endings in the miracidium of Fasciola hepatica

Abstract

The fine structure and organization of the nervous system of the miracidium is described. The central ganglion consists of a mass of nerve fibres with peripherally situated cell bodies. Tracts of fibres run outward from the central mass to the muscles of the body wall and to specialized endings. The individual fibres contain several types of inclusions and synapses are common in the neuropile.Excluding the eyespots, four kinds of specialized nerve endings are described. Two of these types terminate at the body surface and bear ‘cilia’. The other two terminate internally, one type within the body wall and the other type laterally, slightly anterior to the central ganglion. It is suggested that the function of three of the types of ending might be sensory, detecting chemical and mechanical stimuli, and the direction of gravity. The function of the fourth type of ending is problematical but might be secretory.I am most grateful to Dr A. Robards for use of electron microscope facilities and to Mrs J. Denison for technical assistance.