In biology

Biology

Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, a clasper is a male

Male

Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...

 anatomical structure found some groups of animals, used in mating

Mating

In biology, mating is the pairing of opposite-sex or hermaphroditic organisms for copulation. In social animals, it also includes the raising of their offspring. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization...

.

Male cartilaginous fish have claspers formed from the posterior portion of their pelvic fin which serve as intromittent organ

Intromittent organ

An intromittent organ is a general term for an external organ of a male organism that is specialized to deliver sperm during copulation. Intromittent organs are found most often in terrestrial species, as most aquatic species fertilize their eggs externally, although there are...

s used to channel semen

Semen

Semen is an organic fluid, also known as seminal fluid, that may contain spermatozoa. It is secreted by the gonads and other sexual organs of male or hermaphroditic animals and can fertilize female ova...

 into the female's cloaca

Cloaca

In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...

 during mating. The act of mating in some fish including shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s usually includes one of the claspers raised to allow water into the siphon

Siphon (biology)

The term siphon is used for a number of biological structures, either because flowing liquids are involved, or because the object is shaped like a siphon...

 through a specific orifice

Orifice

An orifice is any opening, mouth, hole or vent, as of a pipe, plate, or a body.* Body orifice* Orifice plate* Calibrated orifice* Nozzle* Back Orifice-See also:* Choked flow* Needle valve* Venturi effect* Flow measurement...

. The clasper is then inserted into the vagina

Vagina

The vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...

, where it opens like an umbrella to anchor its position. The siphon then begins to contract exerting water and sperm. Male chimaera

Chimaera

Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, ratfish , spookfish , or rabbitfishes...

s have cephalic claspers on their heads, which are thought to aid in holding the female during mating.

In entomology

Entomology

Entomology is the scientific study of insects, a branch of arthropodology...

, it is a structure in male insects that is used to hold the female during copulation.