New Zealand mudsnails are dioecious. Populations in New Zealand consist of sexual males and both sexual and asexual females, whereas introduced populations are comprised entirely of asexual females.
In their native range, individuals that reproduce sexually are promiscuous. During copulation, the male is found on top of the shell of a female, and the apertures of the two snails are in contact. Females can either maintain their position and proceed with mating or move in a manner that displaces the males. The duration of copulation is typically between 20 minutes and 1.5 hours. Males do not discriminate between sexual females and asexual or parasitically-castrated females, although their genes will not be passed to the offspring of the latter two types of females.
Populations found in the United States consist of triploid females that reproduce asexually by way of parthenogenesis. This type of asexual reproduction is also observed in their native range and leads to populations of genetically identical females or clones in both their native and introduced habitats.
Mating System: polygynandrous (promiscuous)
In New Zealand, reproduction typically occurs every three months. In the western United Staes, reproduction occurs throughout the year, with seasonal peaks during the months of March and October. Females reach sexual maturity at a shell length of 3 mm and produce approximately 230 young per year. Larger females produce more offspring than smaller females, and asexual females produce double the number of female offspring produced by sexual females. This species is ovoviviparous, carrying as many as 10 to 120 eggs at a time for development and giving birth to live snails. Developing embryos are sometimes present within the reproductive system of asexual females at the time of birth.
Breeding interval: In New Zealand, every 3 months.
Breeding season: Year-round
Range number of offspring: 10 to 120.
Average number of offspring: 21.6.
Range age at sexual or reproductive maturity (female): 3 to 6 months.
Key Reproductive Features: seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); parthenogenic ; sexual ; asexual ; fertilization (Internal ); ovoviviparous
This author found no published information on parental investment by New Zealand mudsnails.
Although females retain their eggs until they hatch, it's not known whether the embryos are nourished in anyway other than via the yolk created when each egg is produced.
Parental Investment: female parental care ; pre-fertilization (Provisioning); pre-hatching/birth (Protecting: Female)