Penile spines

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Not to be confused with Baculum.
File:Penisstacheln.jpg
Penile spines of a domestic cat

Many mammalian species have developed keratinized penile spines along the glans or shaft, which may be involved in sexual selection. These spines have been described as being simple, single-pointed structures (macaques) or complex with two or three points per spine (strepsirrhines).[1] Penile spine morphology may be related to mating system.[2][3]

Non-human mammals

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Further information: Spotted hyena § Female genitalia, Fossa (animal) § External genitalia, and Cat § Reproduction

Felines, especially domestic cats, are well known for having penile spines. Upon withdrawal of a cat's penis, the spines rake the walls of the female's vagina, which may serve as a trigger for ovulation.[4][5] Many other felid species have penile spines, but they are relatively small in jaguars and pumas, and do not occur in margays.[6]

Penile spines in chimpanzees and mice are small surface projections made by the piling up of keratinized cell layers in the outermost skin surface.[7][8] They occur in wombats,[9] koalas,[10] spotted hyenas,[11][12] fossas,[13] echidnas,[14] primates,[15][16][17] bats,[18] and several rodent species.[19]

Penile spines are often found in primate species that form copulatory plugs after mating.[20] In galagos, penile spines may form a "genital lock" during copulation.[21]

Humans

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In contrast to chimpanzees, a common morphological variant found in humans called hirsuties coronae glandis, or pearly penile papules, are substantially larger, appear to be an outpocketing of both surface and underlying connective tissue layers, and lack the rich innervation seen in other animals.[22][23] These are sometimes described as vestigial remnants of penile spines.[7] However, the relationship between the structures is still uncertain.[24]

When the hominin lineage split into the genera Homo and Pan, a regulatory DNA sequence associated with the formation of small keratinized penile spines was lost in the Homo lineage. This simplification of penis anatomy may be associated with the sexual habits of humans.[25] In some species which retain full expression, penile spines contribute to increased sexual sensation and quicker orgasms.[26] An hCONDEL (highly conserved region of DNA that contains deletions in humans) located near the locus of the androgen receptor gene may be responsible for the loss of penile spines in humans.[25]

Birds

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The penises of some bird species feature spines and brush-like filaments.[27]

See also

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References

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  1. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  2. ^ Orr, Teri J., and Patricia LR Brennan. "All Features Great and Small—the Potential Roles of the Baculum and Penile Spines in Mammals." Integrative and Comparative Biology (2016): icw057.
  3. ^ Stockley, P. "Sperm competition risk and male genital anatomy: comparative evidence for reduced duration of female sexual receptivity in primates with penile spines. Archived 2017-02-06 at the Wayback Machine" Evolutionary Ecology 16.2 (2002): 123-137.
  4. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  5. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  6. ^ Swanson, W. F., et al. "Reproductive status of endemic felid species in Latin American zoos and implications for ex situ conservation." Zoo Biology 22.5 (2003): 421-441.
  7. ^ a b Hill, W.C.O. Note on the male external genitalia of the chimpanzee. Proc.Zool.Soc. Lond. 116, 129–132 (1946)
  8. ^ Murakami, R. A histological study of the development of the penis of wild-type and androgen-insensitive mice. J. Anat. 153, 223–231 (1987)
  9. ^ Hogan, Lindsay A., Tina Janssen, and Stephen D. Johnston. "Wombat reproduction (Marsupialia; Vombatidae): an update and future directions for the development of artificial breeding technology." Reproduction 145.6 (2013): R157-R173.
  10. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  11. ^ Drea, C. M., et al. "Exposure to naturally circulating androgens during foetal life incurs direct reproductive costs in female spotted hyenas, but is prerequisite for male mating." Proceedings of the Royal Society of London B: Biological Sciences 269.1504 (2002): 1981-1987.
  12. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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  14. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  15. ^ Harcourt, A. H., and J. Gardiner. "Sexual selection and genital anatomy of male primates." Proc. R. Soc. Lond. B 255.1342 (1994): 47-53.
  16. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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  18. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  19. ^ Dewsbury, Donald A. "On the function of the multiple-intromission, multiple-ejaculation copulatory patterns of rodents." Bulletin of the Psychonomic Society 18.4 (1981): 221-223.
  20. ^ Dunham, A. E., and V. H. W. Rudolf. "Evolution of sexual size monomorphism: the influence of passive mate guarding." Journal of evolutionary biology 22.7 (2009): 1376-1386.
  21. ^ Dixson, A. F. "Sexual selection, genital morphology, and copulatory behavior in male galagos." International Journal of Primatology 10.1 (1989): 47-55.
  22. ^ Glicksman, JM and Freeman, RG. Pearly penile papules. A statistical study of incidence. Arch. Dermatol. 93:56-59 (1966)
  23. ^ Agrawal, SK et al. Pearly penile papules: a review. Int. J. Dermatology 43:199-201 (2004)
  24. ^ Penile spines versus pearly penile papules in humans
  25. ^ a b Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
  26. ^ Paleoanthropology, Genetics, and Evolution
  27. ^ Lua error in Module:Citation/CS1/Configuration at line 2172: attempt to index field '?' (a nil value).
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  • Error creating thumbnail: File missing Media related to Lua error in Module:Commons_link at line 62: attempt to index field 'wikibase' (a nil value). at Wikimedia Commons
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