What Is a Clasper?

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Lemon Shark male, showing claspers.
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Claspers are organs that found on male elasmobranchs (sharks, skates, and rays) and Holocephalans (chimaeras). These parts of the animal are vital for the reproduction process.

How Does a Clasper Work?

Each male has two claspers, and they are located along the inner side of the shark or ray's pelvic fin. These play a critical role in helping the animal reproduce. When it mates, the male deposits his sperm into the female's cloaca (the opening that serves as the entrance to the uterus, intestine and urinary tract) via grooves that lie in the upper side of the claspers. The clasper is similar to the penis of a human being. They differ from the human penis, however, because they are not an independent appendage, but rather a deeply grooved cartilaginous extension of the shark's pelvic fins. Plus, sharks have two while humans only have one.

According to some research, sharks use just one clasper during their mating process. It's a hard process to observe, but it often involves using the clasper on the opposite side of the body that is alongside the female.  

Because the sperm is transferred into the female, these animals mate via internal fertilization. This differs from other marine life, who release their sperm and eggs into the water where they join to make new creatures. While most sharks give live birth like humans, others do release eggs that hatch later. The spiny dogfish shark has a gestation period of two years, meaning that it takes two years for the baby shark to develop inside the mother.

If you see a shark or ray up close, you can determine its gender by the presence or absence of claspers. Quite simply, a male will have them and a female will not. It's an easy well to discern the sex of a shark.

Mating is rarely observed in sharks, but in some, the male will nip the female, giving her "love bites" (in some species, females have thicker skin than males). He may turn her over on her side, curl around her or mate parallel to her. Then he inserts a clasper, which may attach to the female via a spur or hook. Muscles push the sperm into the female. From there, the young animals develop in a variety of ways. Some sharks lay eggs while some give birth to live young.

Fun fact:  There is a type of fish that has a similar appendage but it is not part of the pelvic fin as is the case with sharks. Known as a gonopodium, this clasper-like body part is part of the anal fin. These creatures only have one gonopodium, while sharks have the two claspers.

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