Penis fencing

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Two flatworms of the species Pseudobiceros bedfordi preparing for penis fencing. P. bedfordi is exceptional in that it applies sperm onto the partner's skin rather than injecting it. Mating Pseudobiceros bedfordi.png
Two flatworms of the species Pseudobiceros bedfordi preparing for penis fencing. P. bedfordi is exceptional in that it applies sperm onto the partner's skin rather than injecting it.

Penis fencing is a mating behavior engaged in by many species of flatworm, such as Pseudobiceros hancockanus . Species which engage in the practice are hermaphroditic; each individual has both egg-producing ovaries and sperm-producing testes. [1]

Contents

The flatworms "fence" using extendable two-headed dagger-like stylets. These stylets are pointed (and in some species hooked) in order to pierce their mate's epidermis and inject sperm into the haemocoel in an act known as intradermal hypodermic insemination, or traumatic insemination. Pairs can either compete, with only one individual transferring sperm to the other, or the pair can transfer sperm bilaterally. Both forms of sperm transfer can occur in the same species, depending on various factors. [2]

Unilateral sperm transfer

One organism will inseminate the other, with the inseminating individual acting as the "father". The sperm is absorbed through pores or sometimes wounds in the skin from the partner's stylet, causing fertilization in the other, who becomes the "mother". [3] [4] [5] The battle may last for up to an hour in some species. [6]

Parturition, while necessary for successful offspring production, requires a considerable parental investment in time and energy, and according to Bateman's principle, almost always burdens the "mother". Thus, from an optimality model it is usually preferable for an organism to inseminate than to be inseminated. However, in many species that engage in this form of copulatory competition, each "father" will continue to fence with other partners until it is inseminated. In Alderia modesta , individuals will store sperm from several "fencing matches" before laying their eggs, and smaller individuals will more often inseminate a larger partner, with larger individuals spending more energy on laying eggs when paired with a smaller partner on the occasion that they transfer sperm unilaterally. [7]

In the absence of potential mates, some species such as Neobenedenia melleni are capable of reproducing through self-insemination. [8]

Bilateral sperm transfer

Commonly, many hermaphroditic species mutually inseminate, or trade sperm, rather than compete, Chelidonura sandrana as an example. [4] [9] The tiger flatworm, Maritigrella crozieri, also transfers sperm bilaterally. [10] In many species that engage in bilateral insemination, sperm trading is conditional. If one partner "cheats", and does not transfer sperm, the other partner will either prematurely abandon the partner, or will engage in typical mating behavior without transferring sperm. [9] [11] Other species will alternate which partner transfers sperm, engaging in multiple bouts of fencing with the same partner over time. In A. modesta, bilateral sperm transfer is the most common, especially in similarly sized mate pairs. [7]

Other uses

The term is also applied, usually informally, to homosexual activity between two males among bonobos; same-sex genital-genital rubbing is used in bonobo society to cement bonds, reduce conflict, and express communal excitement over food. [12] Several whale species also engage in penis fencing. [13]

See also

Related Research Articles

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<span class="mw-page-title-main">Pseudocerotidae</span> Family of flatworms

Pseudocerotidae is a family of flatworms which includes the Bedford's flatworm. Pseudocerotidae are simple organisms categorized by their oval bodies and tentacles and bright colors. They use the cilia to glide along surfaces. Most commonly referred to as marine flatworms, closely related to the orders Macrostomorpha and Lecithoepitheliata. These organisms have very complex reproductive systems, no blood systems or organs for gas exchange, a simple brain and are hermaphroditic.

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<i>Pseudobiceros</i> Genus of flatworms

Pseudobiceros is a genus of flatworms. Like all flatworms, Pseudobiceros are hermaphrodites. This particular genus engages in penis fencing. When the "winner" touches its penis to the "skin" of the other, insemination occurs, and the "loser" has to bear the burden of motherhood.

<i>Pseudobiceros hancockanus</i> Species of flatworm

Pseudobiceros hancockanus is a species of hermaphroditic marine flatworm in the family Pseudocerotidae. It is also known as Hancock's Flatworm.

<span class="mw-page-title-main">Love dart</span> Darts that some snails shoot into each other during mating

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Pseudobiceros bedfordi is a species of flatworm in the family Pseudocerotidae.

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Thysanozoon nigropapillosum is a species of polyclad flatworms belonging to the family Pseudocerotidae. Some common names include gold-speckled flatworm, marine flatworm, yellow papillae flatworm, yellow-spotted flatworm, and yellow-spotted polyclad flatworm.

<span class="mw-page-title-main">Mating of gastropods</span>

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<i>Alderia modesta</i> Species of gastropod

Alderia modesta is a species of sea slug, a marine gastropod mollusc in the family Limapontiidae. It is found in estuarine habitats and saltmarshes on either side of the North Atlantic and the North Pacific Oceans.

<i>Phestilla minor</i> Species of gastropod

Phestilla minor is a species of sea slug in the Trichechidae family. It is a type of aeolid nudibranch under the Aeolidina suborder. Phestilla minor is a benthic sea slug that is a very small, slow-moving organism found in marine habitats all over the world.

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<span class="mw-page-title-main">Self-insemination</span> Mating behavior

Self-insemination is a mating behavior engaged in by individuals of multiple flatworm species, such as the free-living Macrostomum hystrix. Species that engage in this method of reproduction are hermaphroditic, meaning they possess both male and female reproductive organs. Selfing is referred to as a conditional reproductive strategy in this species, which means that there is a preference to reproduce with a mate.

References

  1. ↑ Leslie Newman. "Fighting to mate: flatworm penis fencing". PBS.
  2. ↑ Schmitt, Valerie; Anthes, Nils; Michiels, Nico K (2007-07-04). "Mating behaviour in the sea slug Elysia timida (Opisthobranchia, Sacoglossa): hypodermic injection, sperm transfer and balanced reciprocity". Frontiers in Zoology. 4: 17. doi: 10.1186/1742-9994-4-17 . ISSN   1742-9994. PMC   1934903 . PMID   17610714.
  3. ↑ Michiels, N.K.; Newman, L.J. (1998). "Sex and violence in hermaphrodites". Nature. 391 (6668): 647. Bibcode:1998Natur.391..647M. doi: 10.1038/35527 .
  4. 1 2 Hermaphrodites duel for manhood, Science News Online. Accessed 14 March 2009. Archived March 26, 2008, at the Wayback Machine
  5. ↑ Sonne, L., Coyote, P., Newman, L. (2001). The shape of life (rm) (Television production). PBS . Retrieved 15 February 2010.
  6. ↑ "World's Weirdest: Flatworm Penis Fencing". National Geographic. Archived from the original on March 12, 2014. Retrieved 14 June 2014.
  7. 1 2 Angeloni, Lisa (21 October 2002). "Sexual selection in a simultaneous hermaphrodite with hypodermic insemination: body size, allocation to sexual roles and paternity" (PDF). Animal Behaviour. 66 (3): 417–426. doi:10.1006/anbe.2003.2255. S2CID   27845838 . Retrieved 1 December 2015.
  8. ↑ Kearn, G., Whittington, I. (2014). Sperm transfer in monogenean (platyhelminth) parasites. Acta Parasitologica, 60(4), 567-600. DOI: 10.1515/ap-2015-0082
  9. 1 2 Dall, SR; Wedell, N (2005-10-11). "Evolutionary Conflict: Sperm Wars, Phantom Inseminations". Current Biology. 15 (19): R801–R803. doi:10.1016/j.cub.2005.09.019. PMID   16213811.
  10. ↑ Danh, Nguyen. "What is the geometric probability of mating success in flatworms, Platyhelminthes?". dspace.nelson.usf.edu. Archived from the original on 2015-12-08. Retrieved 2015-12-02.
  11. ↑ Anthes, Nils; Putz, Annika; Michiels, Nico K. (2005-10-11). "Gender trading in a hermaphrodite". Current Biology. 15 (19): R792–R793. doi: 10.1016/j.cub.2005.09.035 . PMID   16213807.
  12. ↑ De Waal, Frans B.M. (June 1, 2006). "Bonobo Sex and Society". Scientific American. Retrieved 27 October 2018.
  13. ↑ Bruce Bagemihl, Biological Exuberance: Animal Homosexuality and Natural Diversity, St. Martin's Press, 1999; ISBN   978-0312253776
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