Mating plug explained

A mating plug, also known as a copulation plug,^[1] sperm plug, vaginal plug, or sphragis (Latin, from Greek σφραγίς sphragis, "a seal"), is a gelatinous secretion used in the mating of some species. It is deposited by a male into a female genital tract, such as the vagina, and later hardens into a plug or glues the tract together.^{[2] [3]} While females can expel the plugs afterwards, the male's sperm still gets a time advantage in getting to the egg, which is often the deciding factor in fertilization.

The mating plug plays an important role in sperm competition and may serve as an alternative and more advantageous strategy to active mate guarding.^[4] In some species, such a passive mate-guarding strategy may reduce selection on large male size.^[5] Such a strategy may be advantageous because it would allow a male to increase reproductive success by spending more time pursuing new female mates rather than active mate guarding.

Composition

The mating plug of the Bombus terrestris was chemically analyzed and found to consist of palmitic acid, linoleic acid, oleic acid, stearic acid, and cycloprolylproline.^[6] It was found that the acids (without cycloprolylproline) were sufficient by themselves to create the plug. Researchers hypothesize that cycloprolylproline reduces female receptivity to further breeding.

Occurrence in nature

Mating plugs are used by many species, including several primates,^{[7] [8]} kangaroos,^{[9] [10] [11]} bees,^[12] reptiles,^[13] rodents,^{[14] [15] [16]} scorpions,^[17] bats,^[18] and spiders.^[19]

Use of a mating plug as a strategy for reproductive success can also be seen in a few taxa of Lepidoptera and other insects and is often associated with pupal mating.^[20] For example, to protect their paternity, male variable checkerspot butterflies pass a mating plug into the genital opening of females to prevent them from remating.^[21]

The Heliconius charithonia butterfly uses a mating plug in the form of a spermatophore that provides predatory defense chemicals and protein sources for developing eggs.^[22] It also acts as an anaphrodisiac that prevents other males from mating with the female.^[23] Similarly in Parnassius smintheus butterflies, the male deposits a waxy genital plug on the tip of the female's abdomen to prevent the female from mating again.^[24] It contains sperm and important nutrients for the female,^[25] and ensures that the male is the only one to fertilize the female's eggs.

Most species of stingless bees, like Plebeia remota, are only mated once, and thus make use of mating plugs to store all the sperm they collect for future use.

Another species of insect that uses a copulatory plug is Drosophila mettleri, a Sonoran Desert Fly species from the Diptera family. These plugs serve as a means of male-female control during mating interactions.^[26]

A peculiar example of mate plugging occurs in Leucauge mariana spiders. Both male and female participation is required to create a mate plug. The male alone cannot create a functional plug. Female participation in creating a mating plugs, and her presumed benefit from them, have led to multiple studies of sexual selection on the sexual behavior of L. mariana.^[27]

In Thamnophis sirtalis parietalis, commonly known as red-sided garter snakes, males deposit a gelatinous copulatory plug to seal female snake's cloacal opening to prevent re-mating, leakage of the deposited sperm, and alters female pheromonal cues that attract mates. ^[28]

Some cetaceans have folds in the vagina that do not occur in other mammals. The function of these folds is unknown, but it is possible that they form vaginal plugs or retain sperm after copulation.^[29]

See also

• Bulbus glandis

Notes and References

1. Book: Feldhamer, George A. . Mammalogy: Adaptation, Diversity, Ecology . 2007-09-07 . JHU Press . 978-0-8018-8695-9 . en.
2. Book: Leonard . Janet . The Evolution of Primary Sexual Characters in Animals . Cordoba-Aguilar . Alex . 2010-07-16 . Oxford University Press . 978-0-19-971703-3 . en.
3. Book: David Quammen. The Flight of the Iguana: A Sidelong View of Science and Nature. 16 October 2012. Simon and Schuster. 978-1-4767-2873-5.
4. Book: Birkhead, Tim . Promiscuity: An Evolutionary History of Sperm Competition . 2000 . Harvard University Press . 978-0-674-00666-9 . en.
5. Dunham . A. E. . Rudolf . V. H. W. . Evolution of sexual size monomorphism: the influence of passive mate guarding . Journal of Evolutionary Biology . July 2009 . 22 . 7 . 1376–1386 . 10.1111/j.1420-9101.2009.01768.x . 19486235 . 10.1.1.714.2656 . 13617914 .
6. Baer . Boris . Maile . Roland . Schmid-Hempel . Paul . Morgan . E. David . Jones . Graeme R. . Chemistry of a Mating Plug in Bumblebees . Journal of Chemical Ecology . 2000 . 26 . 8 . 1869–1875 . 10.1023/A:1005596707591 . 25735506 .
7. Book: Alan F. Dixson. Primate Sexuality: Comparative Studies of the Prosimians, Monkeys, Apes, and Humans. 26 January 2012. OUP Oxford. 978-0-19-954464-6.
8. Sauther . Michelle L. . Reproductive behavior of free-ranging Lemur catta at Beza Mahafaly Special Reserve, Madagascar . American Journal of Physical Anthropology . April 1991 . 84 . 4 . 463–477 . 10.1002/ajpa.1330840409 .
9. Book: Larry Vogelnest. Rupert Woods. Medicine of Australian Mammals. 18 August 2008. Csiro Publishing. 978-0-643-09928-9.
10. Book: Hugh Tyndale-Biscoe. Marilyn Renfree. Reproductive Physiology of Marsupials. 30 January 1987. Cambridge University Press. 978-0-521-33792-2.
11. Book: Terence Dawson . Kangaroos . 13 July 2013 . 16 April 2012 . Csiro Publishing . 978-0-643-10627-7.
12. Strassmann . J. . The rarity of multiple mating by females in the social Hymenoptera . Insectes Sociaux . March 2001 . 48 . 1 . 1–13 . 10.1007/PL00001737 . 20893433 .
13. King . Richard B. . Jadin . Robert C. . Grue . Michael . Walley . Harlan D. . Behavioural correlates with hemipenis morphology in New World natricine snakes . Biological Journal of the Linnean Society . 25 August 2009 . 98 . 1 . 110–120 . 10.1111/j.1095-8312.2009.01270.x . free .
14. Book: Knobil, Ernst . Knobil and Neill's Physiology of Reproduction . 2006 . Gulf Professional Publishing . 978-0-12-515401-7 . en.
15. Voss . Robert . Male accessory glands and the evolution of copulatory plugs in rodents . Occasional Papers . The Museum of Zoology University of Michigan . June 7, 1979 . 2027.42/57125 .
16. Ittner . Lars M . Götz . Jürgen . 10 May 2007 . Pronuclear injection for the production of transgenic mice . Nature Protocols . 2 . 5 . 1206–1215 . 10.1038/nprot.2007.145 . 17546016 . free.
17. Contreras-Garduno . Jorge . Peretti . Alfredo V. . Cordoba-Aguilar . Alex . Evidence that Mating Plug is Related to Null Female Mating Activity in the Scorpion Vaejovis punctatus . Ethology . February 2006 . 112 . 2 . 152–163 . 10.1111/j.1439-0310.2006.01149.x . 2006Ethol.112..152C .
18. Book: Elizabeth G. Crichton. Philip H. Krutzsch. Reproductive Biology of Bats. 12 June 2000. Academic Press. 978-0-08-054053-5.
19. Knoflach . Barbara . van Harten . Antonius . Tidarren argo sp. nov. (Araneae: Theridiidae) and its exceptional copulatory behaviour: emasculation, male palpal organ as a mating plug and sexual cannibalism . Journal of Zoology . August 2001 . 254 . 4 . 449–459 . 10.1017/S0952836901000954 .
20. The encyclopedia of land invertebrate behaviour By Rod Preston-Mafham, Ken Preston-Mafham. Pg 113.
21. Dickinson . Janis L. . Rutowski . Ronald L. . The function of the mating plug in the chalcedon checkerspot butterfly . Animal Behaviour . July 1989 . 38 . 1 . 154–162 . 10.1016/s0003-3472(89)80074-0 . 53175858 .
22. Cardoso . Márcio Zikán . Gilbert . Lawrence E. . A male gift to its partner? Cyanogenic glycosides in the spermatophore of longwing butterflies (Heliconius) . Naturwissenschaften . 7 September 2006 . 94 . 1 . 39–42 . 10.1007/s00114-006-0154-6 . 16957921 . 39830226 .
23. Estrada . Catalina . Schulz . Stefan . Yildizhan . Selma . Gilbert . Lawrence E. . Sexual Selection Drives The Evolution Of Antiaphrodisiac Pheromones in Butterflies . Evolution . October 2011 . 65 . 10 . 2843–2854 . 10.1111/j.1558-5646.2011.01352.x . 21967426 . 37752151 . free .
24. Book: Shepard . Jon . Guppy . Crispin . Butterflies of British Columbia: Including Western Alberta, Southern Yukon, the Alaska Panhandle, Washington, Northern Oregon, Northern Idaho, and Northwestern Montana . 2011 . UBC Press . 978-0-7748-4437-6 . 13 November 2017 . butterflybook . en.
25. Web site: parnassius smintheus . imnh.isu.edu . 13 November 2017.
26. Alonso-Pimentel H, Tolbert LP, Heed WB. March 1994. Ultrastructural examination of the insemination reaction in Drosophila. Cell and Tissue Research. 275. 3. 467–79. 10.1007/BF00318816. 8137397. 29013736.
27. Hernández. Linda. Aisenberg. Anita. Molina. Jorge. 2018. Hebets. E.. Mating plugs and sexual cannibalism in the Colombian orb-web spider Leucauge mariana. Ethology. en. 124. 1. 1–13. 10.1111/eth.12697. 2018Ethol.124....1H .
28. Crews . David, and William R. Garstka . The Ecological Physiology of a Garter Snake . Scientific American . 1982 . 247 . 5 . 158-71 . JSTOR. 10.1038/scientificamerican1182-158 . 1982SciAm.247e.158C .
29. Book: Perrin . William F. . Encyclopedia of Marine Mammals . Würsig . Bernd . Thewissen . J. G. M. . 2009-02-26 . Academic Press . 978-0-08-091993-5 . en.