Acanthella

The name acanthella (Figs. 1, 2) has been attributed to the Acanthocephalan stage between the acanthor and the larva that is infective to the final (or paratenic) host ( Cystacanth, Acanthocephala). Its growth begins under the serosa of the intermediate host and continues in its body cavity. The morphological changes from the acanthor that has survived the enclosure by the intermediate host’s haemocytes and detached itself from the intestinal wall, to the late acanthella and the “cystacanth” are considerable, e.g., organogenesis occurs as well as a rotation of the worm’s axis through 90 degrees, while the tegument of the acanthor becomes stretched to form the acanthella’s tegument. First, the central nuclear mass begins to split into different bodies which become the primordia of the organs.

Figure 1

Transmission electron micrograph of the outer part of a young acanthella and the surrounding spongy envelope (SE) of microvilli-like outgrowths of the larva’s surface. This envelope has...