Studies on the host–parasite interface of strigeoid trematodes

Abstract

The ultrastructure of the lappets of Apatemon gracilis minor Yamaguti, 1933, has been described. The tegument covering the lappets is characterized by the presence of long seta-like structures and unicellular gland cells which exhibit a holocrine type of secretion. The setae contain extensions of the tegument cytoplasm and are supported by a bundle of fibrils. The unicellular gland cells are pear-shaped with the tapering neck supported by a ring of 50–60 microtubules. The secretion consists of relatively large, membrane bounded bodies containing a fine granular material.The lappets are regarded as representing a specialized host–parasite interface in which adaptation exists for attachment to the host tissue and the discharge of secretion from the parasite at this region. The concept of the specialized host–parasite interface is discussed and extended to include Apatemon gracilis minor.The author wishes to acknowledge the research grant provided by the S.R.C. for the purchase of a vacuum coating unit and an AEI EM 6 electron microscope. The progress of this study was greatly facilitated by the excellent assistance of Mr T. Davies and Miss C. Green. The stereoscan micrograph (P1. 1, fig. 2) is published by permission of the Cambridge Instrument Company.