Adults are viviparous ectoparasites on freshwater fishes. After fertilization, the zygote exhibits serial polyembryony; in its developing uterus a second embryo is already developing, within the uterus of the second embryo a third is developing, and within the uterus of the third embryo a fourth may be developing. After birth, the parasites begins feeding and growing on its host. It soon gives birth to the embryo in its uterus, and then can mate and produce additional offspring. Populations can build up quickly on an infected host. There is no free-living stage, so transfer between hosts requires direct or close contact.