Observations on the reproductive period of the freshwater mussel Potomida littoralis (Unionidae)

Data on the occurrence of gravid Potomida littoralis are presented from museum collections, field samplings and published literature. Gravid animals and released glochidia are recorded to occur between March and October. The smallest gravid animals were four or five years old. The length of the brooding period apparently follows a latitudinal cline. Potomida littoralis is most likely a tachytictic consecutive brooder with unsynchronised broods.