Two unusual unionid hermaphrodites.

In a survey of the gonads of 97 species of North American freshwater mussels representing 59 genera, only four species were found to be hermaphroditic (monoecious). Among several other "occasional" hermaphrodites, two were unique in that the same follicles in the gonads produced eggs and sperm simultaneously. Evidently the control mechanism failed to function normally in these species [Actinonaias ellipsiformis and villosa (formely micromya) iris (Lea)]. This simultaneous production of eggs ans sperm is apparently quite unusual among mollusks.