Britannica
Sources used in this answer
Which animals commonly use external fertilization?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
Reproduction
Fungi produce billions of spores that give rise to new generations of fungi.
External fertilization is a reproductive strategy common among many animals that breed in aquatic environments. In this process, males and females shed their gametes—sperm and eggs—directly into the water, where fertilization occurs outside the female's body.12
Animals that commonly use external fertilization include:
- Most Bony Fishes: The majority of bony fishes (superclass Osteichthyes) are oviparous and release their eggs into the water, where they are fertilized by the male's milt. This is particularly common in pelagic, shore, and freshwater species.2
- Many Invertebrates: Various aquatic invertebrates, including many hydrozoans (such as certain jellyfishes and colonial organisms), utilize external fertilization by shedding eggs directly into the water.3
- Many Amphibians: While reproductive strategies among amphibians are diverse, many anurans (frogs and toads) rely on external fertilization.45
Because the eggs are exposed to the environment, they often face a high mortality rate. To increase the chances of offspring survival, many of these species have evolved behavioral adaptations, such as migration to optimal environments or various forms of parental care. Conversely, terrestrial breeders typically utilize internal fertilization to prevent the desiccation of gametes and embryos.214