The Main Types of Trematode Life Cycles

Abstract

One of the general features of the trematodes is the surprising diversity of their life cycles. This striking polymorphism may be caused by two reasons. On the one hand the effect of the extraordinary diversity is formed by a wide set of various morphological and biological adaptations, existing at different stages of development of digeneans, i.e., a great variety of animal hosts (both invertebrates and vertebrates) and, a broad range of biotopes and ecosystems, utilized by these parasites. Despite the great diversity of the variants, they all manifest a well-expressed biological flexibility of trematodes and, with rare exceptions, do not affect the general scheme of the life cycle, which invariably includes parthenogenetic and hermaphroditic generationsⁱ.