Which animals commonly have both male and female reproductive organs?

In biology, animals that possess both male and female reproductive organs are known as hermaphrodites. This condition is common among many invertebrates, particularly those that are sessile (attached to a surface) or lead a more sluggish lifestyle.12

Examples of animals that are typically hermaphroditic include:

• Annelids: Earthworms and leeches are monoecious, meaning both male and female reproductive organs are present in the same individual.3
• Mollusks: Many gastropods, such as slugs and land snails, are hermaphroditic.1
• Crustaceans: Barnacles are a notable example of hermaphroditic crustaceans.4
• Other Invertebrates: Flatworms and tapeworms are also double-sexed individuals.1

While these animals possess both ovaries and testes, they generally engage in cross-fertilization rather than self-fertilization. Additionally, some species, such as oysters and certain shrimps, exhibit consecutive sexuality, where they change their functional sex during different stages of their life cycle or in response to environmental factors. In vertebrates, true hermaphroditism is generally considered not to exist above the level of amphibians.135