Definition: External fertilization is the process of fertilizing an egg outside of a female’s body. This is done by injecting sperm into the water surrounding an egg that has been removed from a female fish or by inserting a needle directly into the egg.

This type of fertilization is often used in aquaculture to increase the number of eggs that are produced. External fertilization can be observed in amphibians, fish, and some invertebrates.

In amphibians, external fertilization occurs when the male deposits sperm on the skin of the female. The sperm then enters her body through her pores.

External fertilization also occurs in fish when the male releases sperm into the water and it is drawn into the female’s body through her reproductive tract.

In some invertebrates, such as sea urchins and starfish, the male inserts his sperm into the female’s body directly.

Disadvantages of External Fertilization

• There is a greater chance of fertilization failure due to the sperm being exposed to the environment.
• There is a greater risk of infection for both the male and female fish.
• The eggs are more likely to be damaged or destroyed outside of the body.
• The predators or scavengers in the environment may eat the eggs.
• The gametes (sperm and eggs) may not meet if the water is turbulent.
• Survival rates of the fertilized eggs are generally lower than those produced through internal fertilization.

Conclusion

Hence, external fertilization generally has poorer success rates than internal fertilization. This is one of the reasons why it is not commonly used in animals that reproduce sexually.

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