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Snails are mollusks of class Gastropoda, a large and varied invertebrate class. Snails of different species have different anatomies, behaviors and habitats. Some snails are hermaphrodites, some reproduce sexually and some freshwater pond species reproduce asexually. A few species, including the New Zealand mud snail (Potamopyrgus antipodarum), can reproduce both sexually and asexually.
Asexual reproduction requires no fertilization. No sexual activity takes place, nor does fusion of male and female gametes. During a process called parthenogenesis, cell division allows the unfertilized female gamete to develop without auto- or sexual fertilization. This results in a clone, or an exact replica, of the parent snail.
Hermaphrodite snails are often mistaken as asexual. Their internal genital equipment includes male and female organs, as well as hermaphroditic organs. The hermaphroditic gonad generates both egg cells and sperm cells, enabling self-fertilization through the fusion of male and female gametes. Different from asexual reproduction, this is a type of fertilization, although only one animal is providing both the male and the female cells.
Advantages and Disadvantages of Asexual Reproduction
Asexual reproduction is an efficient process, quickly producing an abundance of offspring while using few energy resources. Asexual reproduction can quickly increase a species' numbers in an underpopulated habitat. Each baby snail is genetically the same as the parent. This means that any harmful mutations carried by the parent are passed on to the offspring, possibly endangering the species. Sexually reproduced offspring carry half as many harmful mutations as asexually reproduced descendants. Asexual snails don't evolve in response to environmental changes.
Continuing Studies of Snail Reproduction
The diversity of snail reproduction contains many mysteries ripe for scientific study. Some hermaphrodite species may self-fertilize at times and sexually fertilize eggs at other times. Hermaphrodites are able to change sex as needed. Some snail species reproduce only through male and female sexual activity, while others reproduce only asexually, or asexually when needed and sexually at other times.
- The Living World of Mollusks: The Reproduction of Gastropods
- Newswise: Sex and the Single Snail
- What-When-How.com: Reproduction, Development, and Life History
- Encyclopedia.com: Reproduction, Asexual and Sexual
- Washington State Recreation and Conservation Office: New Zealand Mud Snail
- U.S. Geological Home Page: Nonindigenous Aquatic Species
- Comstock/Comstock/Getty Images