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A pseudo-penis is any structure found on an animal that, while superficially appearing to be a
penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...
, is derived from a different developmental path.


Mammals

In mammals, all intact developmentally typical males have a penis, but the
clitoris The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion – the glans – is at the front junction of the labia minora (inner lips), above the op ...
in the females of the following species is sufficiently enlarged that it is usually termed a pseudo-penis:
spotted hyena The spotted hyena (''Crocuta crocuta''), also known as the laughing hyena, is a hyena species, currently classed as the sole extant member of the genus ''Crocuta'', native to sub-Saharan Africa. It is listed as being of least concern by the IUC ...
, juvenile fossa,
binturong The binturong (''Arctictis binturong'') (, ), also known as the bearcat, is a viverrid native to South and Southeast Asia. It is uncommon in much of its range, and has been assessed as Vulnerable on the IUCN Red List because of a declining pop ...
,
lemur Lemurs ( ) (from Latin ''lemures'' – ghosts or spirits) are wet-nosed primates of the superfamily Lemuroidea (), divided into 8 families and consisting of 15 genera and around 100 existing species. They are endemic to the island of Madagas ...
; ; . and
spider monkey Spider monkeys are New World monkeys belonging to the genus ''Ateles'', part of the subfamily Atelinae, family Atelidae. Like other atelines, they are found in tropical forests of Central and South America, from southern Mexico to Brazil. The ...
. The enlarged clitoris in the fossa is supported by an
os clitoridis The os clitoridis (also called the os clitoris or baubellum) is a bone inside the clitoris of many mammalian taxa. It is absent from the human clitoris, but present in clitoris#Non-human primates, the clitoris of some primates, such as the ring-tail ...
, a bone similar to the
os penis The baculum (also penis bone, penile bone, or ''os penis'', ''os genitale'' or ''os priapi'') is a bone found in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some primates, such as the ...
found in most mammals. However, the fossa's os clitoridis and pseudo-penis shrink as the juvenile female grows, unlike that of other pseudo-penis species. The mammalian pseudo-penis appears to be simply for display, though the spotted hyena is an exception: the female spotted hyena additionally uses her pseudo-penis for urination, sexual intercourse, and to give birth. In addition, this makes it difficult for males to mate without the full co-operation of females, which means that mating preferences of the female are predominant. Spotted hyenas are a matriarchal society, where adult female hyenas dominate the adult male hyenas. Female spotted hyena are also more aggressive than the male spotted hyena. When a male hyena leaves its natal clan, it behaves submissively to all newly encountered hyenas; as a result, when a male hyena settles down with a new clan as a breeding male, it is submissive to all natal clan members. As a result of the submissive behavior in males, it was hypothesized that the male hyena erected its penis as a show of submissiveness. During greetings, hyenas would stand parallel to each other and sniff or lick the erect penis or anal scent gland. There are severe reproductive costs as a result of the female spotted hyena's pseudo-penis. Nearly all female spotted hyena’s first-born cubs are stillborn, as the placenta is not long enough for the extended penile birth canal. In addition, the first birthing process is time-consuming, as it requires the
meatus In anatomy, a meatus (, ),'' OED'' 2nd edition, 1989, as . plural "meatus" or "meatuses",
of the pseudo-penis to tear, allowing the fetus to pass through; as a result, the first-born often die of hypoxia. Female
spider monkey Spider monkeys are New World monkeys belonging to the genus ''Ateles'', part of the subfamily Atelinae, family Atelidae. Like other atelines, they are found in tropical forests of Central and South America, from southern Mexico to Brazil. The ...
s have a clitoris that is referred to as a pseudo-penis because it is especially developed and has a shallow perineal groove that retains and distributes urine droplets as the female moves around. The clitoris of female Geoffroy's spider monkeys is large and protrudes, looking like a penis. This organ, called a pendulous clitoris because of the way it dangles externally, is actually larger than the male flaccid penis. As a result, females are sometimes mistaken for males by human observers. The enlarged clitoris is believed to aid males in determining sexual receptiveness, allowing them to touch the clitoris and smell their fingers to pick up chemical or olfactory cues to the female's reproductive status.


Birds

Only 3% of avian species have a phallus. The most common genital among birds is the cloaca; a direct tract for elimination and reproduction in both of the sexes. Certain bird species, such as the ratites, screamers, waterfowl, and cracids (a family of arboreal galliformes) exhibit a phallus in males. A notable example of a bird with a pseudo-penis is the red-billed buffalo weaver, which do not use their pseudo-penis for direct insertion during copulation; however it does play a part in successful mating and stimulation. Similarly to the red-billed buffalo weaver, the cassowary, a ratite, exhibits a pseudo-penis in both males and females. The male's pseudo-phallus is used to "invaginate", or to push the female’s pseudo-phallus inside-out, and then ejaculates from the cloaca to ensure a successful mating.


Insects

One of the more known examples of a pseudo-penis to occur in the insects is found in the
barklouse Psocoptera are a paraphyletic group of insects that are commonly known as booklice, barklice or barkflies. The name Psocoptera has been replaced with Psocodea in recent literature, with the inclusion of the former order Phthiraptera into Psocode ...
genus ''
Neotrogla ''Neotrogla'' is a genus of barklice noted for its reversed sex roles and organs, traits shared by all species of the genus. Habitat ''Neotrogla'' are found in dry cave systems throughout Brazil. They feed primarily on bat guano. Description ...
''. In this genus, the pseudo-penis plays a part in their rarely-seen sexual reversal. In this case, the male has a vagina-like structure while the female has a pseudo-penis. Some may be confused, wondering why the individuals with a vagina-like structure are considered male while the ones with the pseudo-penis are considered female. This is because even though they have visible outer structures of the opposite sex, their inner structures are consistent to their sex. More important, the males produce sperm and the females produce eggs. Females have a penis-like structure, called the gynosome that has a tube leading into their body to where their genitalia are located. ''Neotrogla'' males have a structure resembling that of a vagina. However, on the inside of their body, they have male genitalia. When the female inserts her organ into the male, the tip of the pseudo penis inflates. When this tip inflates, species specific ridges and spines flare up that match up with the walls of the male's genital chamber. This serves two functions, to stimulate the male's reproductive organs, and to keep the male and female locked together. After they have been locked together, the only way to get the two to part would be to rip off the abdomen of the male. During the lengthy, 40- to 70-hour copulation process, these male genitalia structures ejaculate inside of the male's body. The sperm is then deposited into the female's structure and then travels through a spermathecal duct to where it can fertilize the eggs.


Possible role of androstenedione

Androstenedione Androstenedione, or 4-androstenedione (abbreviated as A4 or Δ4-dione), also known as androst-4-ene-3,17-dione, is an endogenous weak androgen steroid hormone and intermediate in the biosynthesis of estrone and of testosterone from dehy ...
is a hormone that is converted to
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristi ...
by enzymatic activity. It is theorized that the dominance and morphological phenotype of a pseudo-penis observed in female hyenas is due to the presence of prenatal and postnatal androstenedione levels. Prenatal
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This in ...
levels dictate genitalia differences between male and female. Higher levels of
androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This in ...
are observed in the second half of gestation which is theorized to cause masculinization in terms of dominance and aggression in hyenas. Large amounts of androstenedione are produced in hyena ovarian tissues with little aromatase activity allowing the placenta to convert androstenedione to
testosterone Testosterone is the primary sex hormone and anabolic steroid in males. In humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristi ...
. High concentrations of androgens is theorized to virilize the female hyena genitalia and kill ovarian follicles. Postnatal androgen levels dictate growth in genitalia during puberty. Postnatal androgen levels are higher in females than males when they are younger; especially in infancy. These high levels of androstenedione contribute to aggression and dominance and the masculinization of genitalia during puberty.


See also

* Pseudohermaphroditism * Sexual mimicry *
Clitoromegaly Clitoromegaly (or macroclitoris) is an abnormal enlargement of the clitoris that is mostly congenital or acquired, though deliberately induced clitoris enlargement as a form of genital body modification is achieved through various uses of anaboli ...


References

{{reflist Penis Clitoris