Can Seahorses Change Their Gender?

5 min read

Seahorses are unique in many ways. Their shapes do not resemble those of typical fishes. They swim upward, unlike the majority of other fishes. But the most crucial feature that distinguishes them is the fact that the male seahorse is the one that carries fertilized eggs throughout gestation and delivers the young fingerlings.


So, do male seahorses suddenly change to female after fertilization?

Seahorses do not change gender. The female produces the egg, and the male fertilizes it. But after fertilization, the male is responsible for carrying the fertilized egg throughout the gestation period. That is switching roles, not changing gender. Each of the couples still maintains its gender.

So, why are male seahorses responsible for carrying fertilized eggs?

Is this action in line with popular theories of reproduction in animals? We will discuss this in detail, but first, let’s look at the reproductive behavior of seahorses.

How Seahorses Reproduce

Most species of seahorses are monogamous, at least throughout a reproductive season. Once a male and female pair, they stay together. Before copulation takes place, they usually have an extensive courtship.

The courtship behavior can last up to three days. During this time, they will dance side by side. Their body colors will also change.

When they eventually have sex, the male will fertilize the eggs while the eggs are still in the female. But after fertilization, the female will deposit the egg into a pouch in the male.

Once the eggs are deposited inside the male, he will send the female away. However, the female will continue visiting the male every morning till the eggs are hatched. This is to increase the bond between the pair.

The male seahorse will carry the fertilized eggs throughout the gestation period until the eggs develop into fingerlings inside his pouch. This may take up to 45 days.

Once the eggs are hatched, the male will release them and will be ready to immediately mate again. Seahorses can reproduce two broods per month.

The question now is, why do female seahorses transfer the responsibility of carrying the egg to the male partner?

Why Male Seahorses Are Responsible for Carrying Fertilized Eggs

The primary reason the male seahorses carry the fertilized egg is to increase the rate of reproduction. Generally, the mortality rate among fish is very high. That is why fishes usually bear lots of eggs. But in seahorses, it is even worse. Seahorses have one of the highest mortality among fish.

A female seahorse may deposit up to 1500 eggs into the male pouch, but once the eggs are hatched, the fingerlings are left to care for themselves.

Most of them will eventually become food for other marine organisms. Out of the 1500 eggs produced, those that will ultimately develop to the adult stage and reproduce may be less than 10.

Even adult seahorses are not safe. The fish has no means of fighting against predators. It is also among the slowest swimmers among all fish.

The only way it protects itself is by camouflaging. It can change color to match the color of its surroundings. It can also blend perfectly with its environment, hence, deceiving the enemy.


However, many species of seahorses are endangered, and their only way of avoiding being extinct is to reproduce at the highest possible rate. To ensure this, the male and the female adapt to sharing reproductive responsibility.

The moment the female transfers the eggs to the male, she can start producing another set of eggs while the male is busy carrying the eggs.

This ensures there is no gap between the reproductive cycles. The female can be ready to deposit another set of eggs as soon as one set of eggs is hatched. But is this arrangement in line with popular reproductive behavior?

What Experts Say About Reproduction in Seahorses

Many experts have investigated this behavior of seahorses to check if it goes against the popular belief that the gender that contributes the least to reproduction is usually the more aggressive gender.

In most species of organisms, the females typically contribute more energy to reproduction while the males are the more aggressive. The male seahorses are also the more aggressive gender, but do they contribute less to reproduction?

The males will fertilize the eggs, and they will also carry and protect them. This makes it look like they are expending more energy.

However, while different methods were used to determine the energy needed to produce the eggs and the energy needed to fertilize and carry them, it was discovered that the female seahorses still contribute more than the males to fertilization.

It requires way more energy to produce eggs than to carry them. Seahorse behavior does not contradict the reproductive behavior theory.

Other Survival Features of Seahorses

Apart from sharing the reproductive duty to increase the reproductive rate, seahorses also have some other features to keep them alive and increase their natality rate.

One of the significant adaptative features of this fish is its ability to camouflage. When a seahorse sees a predator, it can change its color to match that of its environment.

It can also blend with its surrounding. Fortunately for the seahorse, the visions of most aquatic organisms are not well developed.

Therefore, many predators will not be able to distinguish a camouflaged seahorse from its environment. The predator will pass by it and leave the area.

Another feature is the ability to focus on two different places at the same time. Like many other animals, seahorses have two eyes, but the eyes can work independently of each other.

The fish can focus on the front and the back at the same time. This enables it to detect predators as early as possible.

It also has a long tail that it can use to attach itself to seagrasses to prevent being carried away by the moving water.

During pregnancy, the male seahorse becomes very big. This enlargement can frighten predators and hence protect the fish and the eggs in its pouch.


Seahorses do not change gender, but after fertilization, the female will deposit the eggs into a pouch on the male’s body. The male will carry the fertilized eggs throughout the gestation period until they are hatched.

This enables the female to start producing more eggs as soon as possible. By the time the male delivered the fingerlings, the female is usually ready to deposit another set of eggs.

With this arrangement, the couple can continue making young ones without gaps.

Seahorses are typically monogamous, and they can reproduce throughout their lifetime.

Despite the male fertilizing the eggs and carrying the eggs till they are hatched, the energy used by the female to produce the eggs is still more than the energy used by the male. Therefore, the female seahorse remains the higher contributor to reproduction.

Apart from the male seahorse getting pregnant, other unique features of seahorses include blending with their environment. This helps the fish to avoid predation.

The fish also has a pair of eyes that can focus in a different direction at the same time. This increases its view range.

A seahorse has a tail that can ideally hook to seaweeds. This enables it to remain afloat even when a heavy water wave tries to take it away.

Unfortunately, despite all these surviving features, many species of seahorses are still endangered.

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Pet Aquariums

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