User:AvatarFR/Clitoris animal

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Other animals[edit]

General[edit]

Although the clitoris exists in all mammal species,[1] few detailed studies of the anatomy of the clitoris in non-humans exist.[2] The clitoris is especially developed in fossas,[3] apes, lemurs, and, like the penis, often contains a small bone, the os clitoridis.[4] The clitoris exists in turtles,[5] ostriches,[6] crocodiles,[5] and in species of birds in which the male counterpart has a penis.[5] The clitoris erects in squirrel monkeys during dominance displays, which indirectly influences the squirrel monkeys' reproductive success.[7] In female galagos (bush babies), the clitoris is long and pendulous with a urethra extending through the tip for urination.[8][9] Some intersex female bears mate and give birth through the tip of the clitoris; these species are grizzly bears, brown bears, American black bears and polar bears. Although the bears have been described as having "a birth canal that runs through the clitoris rather than forming a separate vagina" (a feature that is estimated to make up 10 to 20 percent of the bears' population),[10] scientists state that female spotted hyenas are the only non-hermaphroditic female mammals devoid of an external vaginal opening, and whose sexual anatomy is distinct from usual intersex cases.[11] There are also several mole species with a peniform clitoris.[12][13]

Spider monkeys and bonobos[edit]

In spider monkeys, the clitoris is especially developed and has an interior passage, or urethra, that makes it almost identical to the penis, and it retains and distributes urine droplets as the female spider monkey moves around. Scholar Alan F. Dixson stated that this urine "is voided at the bases of the clitoris, flows down the shallow groove on its perineal surface, and is held by the skin folds on each side of the groove".[14] Because spider monkeys of South America have pendulous and erectile clitorises long enough to be mistaken for a penis, researchers and observers of the species look for a scrotum to determine the animal's sex; a similar approach is to identify scent-marking glands that may also be present on the clitoris.[9]

The clitoris of bonobos is larger and more externalized than in most mammals;[15] Natalie Angier said that a young adolescent "female bonobo is maybe half the weight of a human teenager, but her clitoris is three times bigger than the human equivalent, and visible enough to waggle unmistakably as she walks".[16] Female bonobos often engage in the practice of genital-genital (GG) rubbing, which is the non-human form of tribadism that human females engage in. Ethologist Jonathan Balcombe stated that female bonobos rub their clitorises together rapidly for ten to twenty seconds, and this behavior, "which may be repeated in rapid succession, is usually accompanied by grinding, shrieking, and clitoral engorgement"; he added that, on average, they engage in this practice "about once every two hours", and as bonobos sometimes mate face-to-face, "evolutionary biologist Marlene Zuk has suggested that the position of the clitoris in bonobos and some other primates has evolved to maximize stimulation during sexual intercourse".[15]

Spotted hyenas[edit]

With a urogenital system in which the female urinates, mates and gives birth via an enlarged, erectile clitoris, female spotted hyenas are the only female mammalian species devoid of an external vaginal opening.[11]

While female spotted hyenas are sometimes referred to as hermaphrodites or as intersex,[9] and scientists of ancient and later historical times believed that they were hermaphrodites,[9][11][17] modern scientists do not refer to them as such.[11][18] That designation is typically reserved for those who simultaneously exhibit features of both sexes;[18] the genetic makeup of female spotted hyenas "are clearly distinct" from male spotted hyenas.[11][18]

Female spotted hyenas have a clitoris 90 percent as long and the same diameter as a male penis (171 millimeters long and 22 millimeters in diameter),[9] and this pseudo-penis's formation seems largely androgen-independent because it appears in the female fetus before differentiation of the fetal ovary and adrenal gland.[11] The spotted hyenas have a highly erectile clitoris, complete with a false scrotum; author John C. Wingfield stated that "the resemblance to male genitalia is so close that sex can be determined with confidence only by palpation of the scrotum".[7] The pseudo-penis can also be distinguished from the males' genitalia by its greater thickness and more rounded glans.[11] The female possesses no external vagina, as the labia are fused to form a pseudo-scrotum. In the females, this scrotum consists of soft adipose tissue.[7][11][19] Like male spotted hyenas with regard to their penises, the female spotted hyenas have small penile spines on the head of their clitorises, which scholar Catherine Blackledge said makes "the clitoris tip feel like soft sandpaper". She added that the clitoris "extends away from the body in a sleek and slender arc, measuring, on average, over 17 cm from root to tip. Just like a penis, [it] is fully erectile, raising its head in hyena greeting ceremonies, social displays, games of rough and tumble or when sniffing out peers".[20]

Male and female reproductive systems of the spotted hyena, from Schmotzer & Zimmerman, Anatomischer Anzeiger (1922). Abb. 1 (Fig. 1.) Male reproductive anatomy. Abb. 2 (Fig. 2.) Female reproductive anatomy.[21] Principal abbreviations (from Schmotzer & Zimmerman) are: T, testis; Vd, vas deferens; BU, urethral bulb; Ur, urethra; R, rectum; P, penis; S, scrotum; O, ovary; FT, tuba Fallopii; RL, ligament uteri; Ut, uterus; CC, Corpus clitoris. Remaining abbreviations, in alphabetical order, are: AG, parotid analis; B, vesica urinaria; CG, parotid Cowperi; CP, Corpus penis; CS, corpus spongiosum; GC, glans; GP, glans penis; LA, levator ani muscle; Pr, prepuce; RC, musculus retractor clitoris; RP, Musculus retractor penis; UCG, Canalis urogenital.

Due to their higher levels of androgen exposure, the female hyenas are significantly more muscular and aggressive than their male counterparts; social-wise, they are of higher rank than the males, being dominant or dominant and alpha, and the females who have been exposed to higher levels of androgen than average become higher-ranking than their female peers. Subordinate females lick the clitorises of higher-ranked females as a sign of submission and obedience, but females also lick each other's clitorises as a greeting or to strengthen social bonds; in contrast, while all males lick the clitorises of dominant females, the females will not lick the penises of males because males are considered to be of lowest rank.[19][22]

The urethra and vagina of the female spotted hyena exit through the clitoris, allowing the females to urinate, copulate and give birth through this organ.[7][11][20][23] This trait makes mating more laborious for the male than in other mammals, and also makes attempts to sexually coerce (physically force sexual activity on) females futile.[19] Joan Roughgarden, an ecologist and evolutionary biologist, said that because the hyena's clitoris is higher on the belly than the vagina in most mammals, the male hyena "must slide his rear under the female when mating so that his penis lines up with [her clitoris]". In an action similar to pushing up a shirtsleeve, the "female retracts the [pseudo-penis] on itself, and creates an opening into which the male inserts his own penis".[9] The male must practice this act, which can take a couple of months to successfully perform.[22] Female spotted hyenas exposed to larger doses of androgen have significantly damaged ovaries, making it difficult to conceive.[22] After giving birth, the pseudo-penis is stretched and loses much of its original aspects; it becomes a slack-walled and reduced prepuce with an enlarged orifice with split lips.[24] Approximately 15% of the females die during their first time giving birth, and over 60% of their species' firstborn young die.[9]

A 2006 Baskin et al. study concluded, "The basic anatomical structures of the corporeal bodies in both sexes of humans and spotted hyenas were similar. As in humans, the dorsal nerve distribution was unique in being devoid of nerves at the 12 o'clock position in the penis and clitoris of the spotted hyena" and that "[d]orsal nerves of the penis/clitoris in humans and male spotted hyenas tracked along both sides of the corporeal body to the corpus spongiosum at the 5 and 7 o'clock positions. The dorsal nerves penetrated the corporeal body and distally the glans in the hyena" and, in female hyenas, "the dorsal nerves fanned out laterally on the clitoral body. Glans morphology was different in appearance in both sexes, being wide and blunt in the female and tapered in the male".[23]

Cats, sheep and mice[edit]

Researchers studying the peripheral and central afferent pathways from the feline clitoris concluded that "afferent neurons projecting to the clitoris of the cat were identified by WGA-HRP tracing in the S1 and S2 dorsal root ganglia. An average of 433 cells were identified on each side of the animal. 85 percent and 15 percent of the labeled cells were located in the S1 and S2 dorsal root ganglia, respectively. The average cross sectional area of clitoral afferent neuron profiles was 1.479±627 μm2." They also stated that light "constant pressure on the clitoris produced an initial burst of single unit firing (maximum frequencies 170–255 Hz) followed by rapid adaptation and a sustained firing (maximum 40 Hz), which was maintained during the stimulation" and that further examination of tonic firing "indicate that the clitoris is innervated by mechano-sensitive myelinated afferent fibers in the pudental nerve which project centrally to the region of the dorsal commissure in the L7-S1 spinal cord".[25]

The external phenotype and reproductive behavior of 21 freemartin sheep and two male pseudohermaphrodite sheep were recorded with the aim of identifying any characteristics that could predict a failure to breed. The vagina's length and the size and shape of the vulva and clitoris were among the aspects analyzed. While the study reported that "a number of physical and behavioural abnormalities were detected," it also concluded that "the only consistent finding in all 23 animals was a short vagina which varied in length from 3.1 to 7.0 cm, compared with 10 to 14 cm in normal animals."[26]

In a study concerning the clitoral structure of mice, the mouse perineal urethra was documented as being surrounded by erectile tissue forming the bulbs of the clitoris.[2] The researchers stated, "In the mouse, as in human females, tissue organization in the corpora cavernosa of the clitoris is essentially similar to that of the penis except for the absence of a subalbugineal layer interposed between the tunica albuginea and the erectile tissue."[2]

  1. ^ Cite error: The named reference Balcombe was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference Martin-Alguacil was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference Hawkins was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Angier_Hall_Goodman was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Fishbeck was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Kotpal was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference Wingfield 2006 p2023 was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference Bagemihl was invoked but never defined (see the help page).
  9. ^ a b c d e f g Cite error: The named reference Roughgarden 2004 pp37-40 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Girshick_Roughgarden was invoked but never defined (see the help page).
  11. ^ a b c d e f g h i Cite error: The named reference Glickman was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Sinclair was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Rubenstein was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Dixson was invoked but never defined (see the help page).
  15. ^ a b Cite error: The named reference Balcombe 2011 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Angier was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Rosenzweig was invoked but never defined (see the help page).
  18. ^ a b c Cite error: The named reference Blumberg was invoked but never defined (see the help page).
  19. ^ a b c Cite error: The named reference Szykman was invoked but never defined (see the help page).
  20. ^ a b Cite error: The named reference Blackledge 2003 p90 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Schmotzer was invoked but never defined (see the help page).
  22. ^ a b c Cite error: The named reference Carey was invoked but never defined (see the help page).
  23. ^ a b Cite error: The named reference Baskin was invoked but never defined (see the help page).
  24. ^ Cite error: The named reference Rosevear 1974 pp357–358 was invoked but never defined (see the help page).
  25. ^ Cite error: The named reference Kawatani was invoked but never defined (see the help page).
  26. ^ Cite error: The named reference Smith was invoked but never defined (see the help page).
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