The occurrence of precociously developed metacercariae among digenetic trematodes has been noted by numerous investigators both here and abroad. Included in the literature are references to species representing more than a dozen families which have been recorded as exhibiting this phenomenon. Among many groups it manifests itself in progenetic development, i. e., the attainment of sexual maturity by metacercariae (or cercariae occasionally) while still within the first intermediate host, with resultant egg production, and at times the appearance of viable miracidia within such metacercariae. Buttner (1950, 1951) in an intensive study of progenesis among digenetic trematodes provides experimental evidence indicating that some life cycles may be considerably shortened through such progenetic development of metacercariae. Other families of digenetic trematodes, among them the Echinostomatidae, include species in which encystment of metacercariae within rediae is of common occurrence, even though such metacercariae do not exhibit sexual maturity.
Proceedings of the Iowa Academy of Science
©1954 Iowa Academy of Science, Inc.
Ulmer, Martin J.
"Precociously Developed Brachylaimid Metacercariae within Sporocysts,"
Proceedings of the Iowa Academy of Science, 61(1), 631-635.
Available at: https://scholarworks.uni.edu/pias/vol61/iss1/82