. Animal Ecology. Animal ecology. OPHIOTAmA PEIf6P/CUA LIFE CYCUe. FIG. 12-2 Life cycle of a snake tapeworm. The eggs are voided into the water with the feces of the snake, where they are ingested by the copepod Cyclops (lower right). A procercoid (middle right) develops in the copepod, from the egg. If the copepod is eaten by a fish, the procercoid changes into a plerocercoid (upper right) and becomes encysted in the liver or mesenteries. When the fish is eaten by a water snake, the mature tapeworm develops (upper left). Other intermediary hosts are tadpoles and frogs (Thomas 1944). Host spec
. Animal Ecology. Animal ecology. OPHIOTAmA PEIf6P/CUA LIFE CYCUe. FIG. 12-2 Life cycle of a snake tapeworm. The eggs are voided into the water with the feces of the snake, where they are ingested by the copepod Cyclops (lower right). A procercoid (middle right) develops in the copepod, from the egg. If the copepod is eaten by a fish, the procercoid changes into a plerocercoid (upper right) and becomes encysted in the liver or mesenteries. When the fish is eaten by a water snake, the mature tapeworm develops (upper left). Other intermediary hosts are tadpoles and frogs (Thomas 1944). Host specificity Copepods are of all parasites the most ubiqui- tous in their host relationships, being reported from various invertebrate groups and from fish. Most par- asitic genera, however, are adapted to hosts of one phylum only. The acanthocephalans Gracilisentis and Tanarhamphns are. yet more specific, normally found only in the gizzards of shad fish; Octospinifer is found only in catostomids; Eocollis, only in cen- trarchids. Each order of birds possesses its own particular species of tapeworms; this is true even when several orders of birds live in the same habi- tats, as do, for instance, grebes, loons, herons, ducks, waders, flamingoes, and cormorants (Baer 1951). Species of flagellate protozoans that occur in termite alimentary tracts are largely host-specific (Kirby 1937). However, considerable caution needs to be exercised in assigning host specificity to protozoans. Many species have invaded more than one taxonomic host group: and often several species of a single genus of Protozoa frequent the same host species. Some species of gall wasps attack only one species of oak. Where a single species parasitizes two or more host species, the shape and structure of the gall formed around the egg and larva on both hosts is essentially similar. When several insects are found on the same oak, each kind of parasite produces its own characteristic gall form. Apparently the charac- te
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