Copulatory organ

(anatomy) An organ employed by certain male animals for insemination.

An organ utilized by certain male vertebrates for insemination, that is, to deposit spermatozoa directly into the female reproductive tract. In fish, internal fertilization is restricted to certain groups. The pelvic fin of male elasmobranchs and holocephalians is modified for the transmission of sperm and is known as the clasper or clasping organ. A pair of anterior claspers (illus. a) and a frontal clasper which protrudes from the head occur among holocephalians in addition to the modified pelvic clasper of elasmobranchs. The anal fin of teleosts, in which copulation occurs, may be elongated to form a gonopodium.

dogfish (Squalus). Glans penis of (b) opossum, (c) ram, (d) bull, (e) short-tailed shrew, (f) man, (g) Echidna.">
Vertebrate copulatory organs. (a) Clasper of dogfish (Squalus). Glans penis of (b) opossum, (c) ram, (d) bull, (e) short-tailed shrew, (f) man, (g) Echidna.

Hemipenes which can be everted during copulation are common to both snakes and lizards; however, these structures lack erectile tissue. Turtles and crocodiles possess a single penis with associated erectile tissue, the corpora cavernosa, which becomes distended with blood. A few species of birds have a penis; among these are the ostriches and anseriforms. The penis is present in all mammals.

The copulatory organ (illus. b–g) is variously modified morphologically. Among certain mammals such as rodents, bats, whales, some carnivores, and lower primates, a penis bone, the os priapi or baculum, occurs, increasing the rigidity of the penis. See also Penis.