Two Strategies of Acanthocephalan Interrelations with Paratenic Hosts

Resumo

Data available on the peculiarities of the tegument structure and encapsulation of the acanthocephalans Corynosoma strumosum (Palaeacanthocephala, Polymorphidae) and Sphaerirostris picae (Palaeacanthocephala, Centrorhynchidae) in paratenic hosts are summarized. Corynosomes are shown to have a capsule structure varying from fibroblastic to leukocytal depending on the species of the paratenic host (sea fish). The characteristic thick glycocalix layer may or may not develop on the tegument surface of corynosomes surrounded by the leukocytal capsule in the hosts of different species. The acanthocephalan S. picae in a paratenic host (lizard) is also surrounded by a leukocytal capsule; however, no characteristic glycocalyx layer is formed on its tegument surface. Such a glycocalyx supposedly represents a protective reaction of the parasite to cellular encapsulation, but in the case of its absence the protective mechanism remains unclear. Based on these results, a hypothesis about two strategies of interrelations between acanthocephalans and paratenic hosts is advanced. According to the first strategy, the acanthocephalan (C. strumosum in the fish of the majority of the species studied), regardless of the structure of the capsule formed around it, is covered with a thick layer of glycocalyx, while the cells of the inner part of the capsule are destroyed. When invading paratenic hosts of other species (C. strumosum in flatfishes, as well as in experimentally infested aquarium fish and lizards, S. picae in lizards), the second strategy is realized: the acanthocephalan is surrounded by a leukocytal capsule; however, a thick layer of glycocalyx on its surface is not formed and the capsule’s cells are not destroyed.