Tegument and external Features of Schistosoma (with particular reference to ultrastructure)

The integument (hereafter tegument) of adult and larval schistosomes has attracted substantial interest from the schistosomiasis research community. This thin layer, approximately 1-5 μm thick, is the primary physical delineating interface of the parasite, with other borders being the lining of the internal digestive canal (Wilson and Xiaohong Li, Chapter 11), the excretory system (Kusel, Chapter 16) and the reproductive system (Jones et al., Chapter 13). This syncytial layer provokes interest because it is considered a primary target for drug and vaccine studies (Loukas et al. 2007). Further, the interest arises from the intense remodeling of the layer that occurs as the parasite invades a new host (Hockley and McLaren 1973), because of multifaceted functions (Skelly and Wilson 2006) and exquisite structure. In this chapter, we will examine each of these relevant facets and will build on the strong structural knowledge that commenced during the 1960’s and 1970’s corresponding with the expansion of electron microscopy techniques for biological applications. The tegument has been the subject of numerous reviews (Hockley 1973; Hockley and McLaren 1973; Jones et al. 2004; Kusel et al. 2007; Loukas et al. 2007; Skelly and Wilson 2006; Wilson 2012a, 2012b) among many others) and the reader is referred to these others for further details and structural and functional aspects of the tissue.