Generally, acanthocephalans that have a short neck do not deeply penetrate into the host’s intestinal wall with their praesoma, i.e., they do not create lesions reaching as deep as the muscular layers of the intestinal wall (Acanthocephala, Fig. 4). In contrast, many acanthocephalans possess a long neck which may comprise a bulbus as an inflated part of the neck (Figs. 1 and 2). The bulbus functions as a dowel enabling the worm to occupy a permanent point of attachment at one site. Long-necked species perforate the tunica muscularis or the whole intestinal wall of the hosts with their praesoma (Fig. 1). In small hosts with thin intestinal wall parts of the metasoma (Fig. 3) or entire worms may be found in extraintestinal positions. The perforation of the intestinal wall may be supported by proteolytic enzymes.