Freshwater mussels in Brazil: past, present and future, at least, we hope they have one

摘要

The unionids (order Unionoida Stoliczka, 1871) comprise a highly specialized and diverse group among the Bivalvia, containing six families: Unionidae, Margaritiferidae, Hyriidae, Mycetopodidae, Iridinidae and Etheriidae. Since the Permian/ Triassic Period (± 250 million years) they have become adapted exclusively to the freshwater environment. Besides this aspect they are interesting for other characteristics, perhaps the most fascinating is the occurrence in the life cycle of a unique larval stage known as glochidium or lasidium that typically parasitizes aquatic vertebrates, usually fishes.