Do Shrimp Have Testicles?

Shrimp are fascinating creatures that have some unique reproductive biology. Specifically, many shrimp species are protandrous hermaphrodites, meaning they start life as males and then transition to become females later on. This brings up an interesting question – do shrimp have testicles if they start as males? Let’s take a closer look at shrimp reproduction and anatomy to understand more.

Shrimp as Protandrous Hermaphrodites

Many shrimp species, such as Northern shrimp and Caribbean coral shrimp, are born male and have male gonads called testes. They mate with female shrimp and function reproductively as males. However, after a period of time, usually around 2-3 years after hatching, the testes undergo a change. They transition from testes to ovaries, becoming female gonads.

At this point, the shrimp stops functioning as a male and starts functioning reproductively as a female. It can now produce eggs and mate with male shrimp. So shrimp do have testicles when they are in the initial male phase of their lives. But the testicles convert to ovaries later on.

Why Do Shrimp Change Sex?

This interesting ability of sex change in shrimp is an evolutionary adaptation. For species where the females are larger than the males, it allows the shrimp to mate when young and small as a male. Then they can become female later on when they are larger, producing more eggs.

Becoming female essentially increases their reproductive success. Larger females can produce many more eggs than smaller males can produce sperm. Therefore, transitioning from male to female maximizes the number of offspring a shrimp can have in its lifetime.

Shrimp Testes Location and Structure

In young male shrimp the testes are located inside the cephalothorax which is the head section of the shrimp body. There is a pair of testes, one on each side of the body. The testes are elongated organs that run longitudinally partway down the cephalothorax region.

The testes contain many small lobules where sperm are produced. The sperm mature and are then stored in a part of the testis called the vas deferens. From there, sperm can be released through openings on the underside of the shrimp’s body to fertilize female shrimp eggs.

The Sex Change Process

When male shrimp reach a certain age, size, or social status, their testes begin transforming into ovaries in a process influenced by hormones. The testicular lobules and sperm-producing tissue break down and are replaced by ova-producing ovarian tissue.

This process occurs progressively in phases until the entire testis consists of ovarian tissue. Now the shrimp has completely transitioned from a reproductive male to a reproductive female.

Mating and Spawning

Mature male shrimp use their first pair of pleopods (swimmerets) to transfer sperm packets to females during mating. The females store the sperm internally until they are ready to spawn their eggs.

Spawning typically occurs offshore for many shrimp species. The female releases her eggs, which get fertilized by stored sperm as they pass through her oviduct. The eggs hatch into free-floating planktonic larvae that eventually mature into juvenile shrimp.

Why Don’t All Shrimp Change Sex?

While many shrimp species exhibit protandrous hermaphroditism as described above, not all do. Some shrimp remain one sex their entire lives, including certain shrimp farmed for human consumption like Whiteleg shrimp.

For rarer shrimp species, changing sex likely provides a reproductive advantage. But for abundant species, staying one sex maximizes reproductive success since they can easily find mates.