Internal fertilization

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Internal fertilization is the union of an egg and sperm cell during sexual reproduction inside the female body. Internal fertilization, unlike its counterpart, external fertilization, brings more control to the female with reproduction. [1] For internal fertilization to happen there needs to be a method for the male to introduce the sperm into the female's reproductive tract.

Contents

Most taxa that reproduce by internal fertilization are gonochoric. [2] : 124–125  In mammals, reptiles, and certain other groups of animals, this is done by copulation, an intromittent organ being introduced into the vagina or cloaca. [3] [4] In most birds, the cloacal kiss is used, the two animals pressing their cloacas together while transferring sperm. [5] Salamanders, spiders, some insects and some molluscs undertake internal fertilization by transferring a spermatophore, a bundle of sperm, from the male to the female. Following fertilization, the embryos are laid as eggs in oviparous organisms, or continue to develop inside the reproductive tract of the mother to be born later as live young in viviparous organisms.

Evolution of internal fertilization

Internal fertilization evolved many times in animals. [2] : 2  According to David B. Dusenbery all the features with internal fertilization were most likely a result from oogamy. [6] It has been argued that internal fertilization evolve because of sexual selection through sperm competition. [7]

In amphibians, internal fertilization evolved from external fertilization. [8]

Methods of internal fertilization

Fertilization which takes place inside the female body is called internal fertilization in animals is done through the following different ways: [9] [10] [11]

Expulsion

At some point, the growing egg or offspring must be expelled. There are several possible modes of reproduction. These are traditionally classified as follows:

Advantages to internal fertilization

Internal fertilization allows for:

Disadvantages to internal fertilization

Fish

Some species of fish like guppies have the ability to internally fertilize, this process happens by the male inserting a tubular fin into the female's reproductive opening and then will deposit sperm into her reproductive tract. There are other species of fish that are mouthbrooders which means that one fish puts the eggs in its mouth for incubation. A certain type of fish that is a mouthbrooder is called cichlids and many of them are maternal mouthbrooders. The process for this is the female would lay the egg and pick it up in her mouth. Then the males will encourage the female to open her mouth so they can fertilize the eggs while it is in the female's mouth. [25] Internal fertilization in cartilaginous fishes contains the same evolutionary origin as reptiles, birds, and mammals that internally fertilize. Also in these internally fertilizing fish while the sperm is transferred to the reproductive tract there is no noticeable change in tonality. [26]

Amphibians

Most amphibians have external fertilization but there is an exception to some like salamanders which mostly have internal fertilization. Salamanders do not use intercourse for sexual reproduction due to their lack of external penis. Rather, the male salamander produces an encased capsule of sperm and nutrients called a spermatophore. The male deposits a spermatophore on the ground and the female will pick it up with her cloaca (a combined urinary and genital opening) and fertilize her eggs with it. [25] Over time amphibians have been found evolving to increasing internal fertilization.[ citation needed ] Within amphibians, it is common for high vertebrates to internally fertilize because of the transition from water to land during vertebrate evolution. There is an advantage for the amphibians who are internally fertilizing allowing for the selection of a time and place for reproduction. [20]

Birds

Most birds do not have penises, but achieve internal fertilization via cloacal contact (or “cloaca kiss”). In these birds, males and females contact their cloacas together, typically briefly, and transfer sperm to the female. However, water fowls such as ducks and geese have penises and are able to use them for internal fertilization. [25] While birds have internal fertilization, most species no longer have phallus structures. This makes them the only vertebrate taxon to fall into both categories of lacking the phallus but participating in internal fertilization. [27]

See also

Related Research Articles

<span class="mw-page-title-main">Sex</span> Trait that determines an organisms sexually reproductive function

Sex is the trait that determines whether a sexually reproducing organism produces male or female gametes. During sexual reproduction, a male and a female gamete fuse to form a zygote, which develops into an offspring that inherits traits from each parent. By convention, organisms that produce smaller, more mobile gametes are called male, while organisms that produce produce larger, non-mobile gametes are called female. An organism that produces both types of gamete is hermaphrodite.

<span class="mw-page-title-main">Sex organ</span> Biological part involved in sexual reproduction

A sex organ, also known as a reproductive organ, is a part of an organism that is involved in sexual reproduction. Sex organs constitute the primary sex characteristics of an organism. Sex organs are responsible for producing and transporting gametes, as well as facilitating fertilization and supporting the development and birth of offspring. Sex organs are found in many species of animals and plants, with their features varying depending on the species.

<span class="mw-page-title-main">Mating</span> Process of pairing in biology

In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. Fertilization is the fusion of two gametes. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization. Mating may also lead to external fertilization, as seen in amphibians, fishes and plants. For most species, mating is between two individuals of opposite sexes. However, for some hermaphroditic species, copulation is not required because the parent organism is capable of self-fertilization (autogamy); for example, banana slugs.

<span class="mw-page-title-main">Cloaca</span> Posterior opening in zoology

A cloaca, pl.: cloacae, is the rear orifice that serves as the only opening for the digestive, reproductive, and urinary tracts of many vertebrate animals. All amphibians, reptiles, birds, and a few mammals, have this orifice, from which they excrete both urine and feces; this is in contrast to most placental mammals, which have two or three separate orifices for evacuation and reproduction. Excretory openings with analogous purpose in some invertebrates are also sometimes called cloacae. Mating through the cloaca is called cloacal copulation and cloacal kissing.

<span class="mw-page-title-main">Common mudpuppy</span> Species of salamander

The common mudpuppy is a species of salamander in the family Proteidae. It lives an entirely aquatic lifestyle in parts of North America in lakes, rivers, and ponds. It goes through paedomorphosis and retains it external gills. Because skin and lung respiration alone is not sufficient for gas exchange, the common mudpuppy must rely on external gills as its primary means of gas exchange. It is usually a rusty brown color and can grow to an average total length of 13 in (330 mm). It is a nocturnal creature, and is active during the day only if the water in which it lives is murky. Its diet consists of almost anything it can get into its mouth, including insects, mollusks, and earthworms. Once a female common mudpuppy reaches sexual maturity at six years of age, she can lay an average of 60 eggs. In the wild, the average lifespan of a common mudpuppy is 11 years.

External fertilization is a mode of reproduction in which a male organism's sperm fertilizes a female organism's egg outside of the female's body. It is contrasted with internal fertilization, in which sperm are introduced via insemination and then combine with an egg inside the body of a female organism. External fertilization typically occurs in water or a moist area to facilitate the movement of sperm to the egg. The release of eggs and sperm into the water is known as spawning. In motile species, spawning females often travel to a suitable location to release their eggs.

<span class="mw-page-title-main">Fish reproduction</span> Reproductive physiology of fishes

Fish reproductive organs include testes and ovaries. In most species, gonads are paired organs of similar size, which can be partially or totally fused. There may also be a range of secondary organs that increase reproductive fitness. The genital papilla is a small, fleshy tube behind the anus in some fishes, from which the sperm or eggs are released; the sex of a fish can often be determined by the shape of its papilla.

<span class="mw-page-title-main">Oviparity</span> Animals that lay their eggs, with little or no other embryonic development within the mother

Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings known as hatchlings with little or no embryonic development within the mother. This is the reproductive method used by most animal species, as opposed to viviparous animals that develop the embryos internally and metabolically dependent on the maternal circulation, until the mother gives birth to live juveniles.

<span class="mw-page-title-main">Hemipenis</span> Male sex organ in squamate reptiles

A hemipenis is one of a pair of intromittent organs of male squamates. Hemipenes are usually held inverted within the body, and are everted for reproduction via erectile tissue, much like that in the human penis. They come in a variety of shapes, depending on species, with ornamentation such as spikes.

<span class="mw-page-title-main">Ocoee salamander</span> Species of amphibian

The ocoee salamander is a species of salamander in the family Plethodontidae. This salamander has a variety of colors and patterns, and got its name from Tennessee state wildflower. Its natural habitats are temperate forests, rivers, intermittent rivers, freshwater springs and wet rocks in mountainous areas of the Southeastern United States. It was first described by Nicholls in 1949. They are territorial and feed on small invertebrates. It is widely distributed in the southeastern United States and is listed as "Least Concern" by the International Union for Conservation of Nature.

<span class="mw-page-title-main">Spawn (biology)</span> Process of aquatic animals releasing sperm and eggs into water

Spawn is the eggs and sperm released or deposited into water by aquatic animals. As a verb, to spawn refers to the process of freely releasing eggs and sperm into a body of water ; the physical act is known as spawning. The vast majority of non-mammalian, non-avian and non-reptilian aquatic and/or amphibious lifeforms reproduce through this process, including the:

The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.

<span class="mw-page-title-main">Sexual reproduction</span> Biological process

Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes.

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

The reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals. Their reproductive strategies also vary greatly.

An intromittent organ is any external organ of a male organism that is specialized to deliver sperm during copulation. Intromittent organs are found most often in terrestrial species, as most non-mammalian aquatic species fertilize their eggs externally, although there are exceptions. For many species in the animal kingdom, the male intromittent organ is a hallmark characteristic of internal fertilization.

<span class="mw-page-title-main">Female sperm storage</span>

Female sperm storage is a biological process and often a type of sexual selection in which sperm cells transferred to a female during mating are temporarily retained within a specific part of the reproductive tract before the oocyte, or egg, is fertilized. This process takes place in some species of animals, but not in humans. The site of storage is variable among different animal taxa and ranges from structures that appear to function solely for sperm retention, such as insect spermatheca and bird sperm storage tubules, to more general regions of the reproductive tract enriched with receptors to which sperm associate before fertilization, such as the caudal portion of the cow oviduct containing sperm-associating annexins. Female sperm storage is an integral stage in the reproductive process for many animals with internal fertilization. It has several documented biological functions including:

<span class="mw-page-title-main">Sexual selection in amphibians</span> Choice of and competition for mates

Sexual selection in amphibians involves sexual selection processes in amphibians, including frogs, salamanders and newts. Prolonged breeders, the majority of frog species, have breeding seasons at regular intervals where male-male competition occurs with males arriving at the waters edge first in large number and producing a wide range of vocalizations, with variations in depth of calls the speed of calls and other complex behaviours to attract mates. The fittest males will have the deepest croaks and the best territories, with females making their mate choices at least partly based on the males depth of croaking. This has led to sexual dimorphism, with females being larger than males in 90% of species, males in 10% and males fighting for groups of females.

Parthenogenesis is a form of reproduction where eggs develop without fertilization, resulting in unisexual species. This phenomenon is closely related with reproductive modes such as hybridogenesis, where fertilization occurs, but the paternal DNA is not passed on. Among amphibians, it is seen in numerous frog and salamander species, but has not been recorded in caecilians.

Cryptic female choice is a form of mate choice which occurs both in pre and post copulatory circumstances when females in certain species use physical or chemical mechanisms to control a male's success of fertilizing their ova or ovum; i.e. by selecting whether sperm are successful in fertilizing their eggs or not. It occurs in internally-fertilizing species and involves differential use of sperm by females when sperm are available in the reproductive tract.

Gynogenesis, a form of parthenogenesis, is a system of asexual reproduction that requires the presence of sperm without the actual contribution of its DNA for completion. The paternal DNA dissolves or is destroyed before it can fuse with the egg. The egg cell of the organism is able to develop, unfertilized, into an adult using only maternal genetic material. Gynogenesis is often termed "sperm parasitism" in reference to the somewhat pointless role of male gametes. Gynogenetic species, "gynogens" for short, are unisexual, meaning they must mate with males from a closely related bisexual species that normally reproduces sexually.

References

  1. 1 2 Alonzo SH, Stiver KA, Marsh-Rollo SE (August 2016). "Ovarian fluid allows directional cryptic female choice despite external fertilization". Nature Communications. 7 (1): 12452. Bibcode:2016NatCo...712452A. doi:10.1038/ncomms12452. PMC   4990696 . PMID   27529581.
  2. 1 2 Leonard, Janet; Cordoba-Aguilar, Alex (2010-07-16). The Evolution of Primary Sexual Characters in Animals. Oxford University Press. ISBN   978-0-19-971703-3.
  3. ↑ Hyman LH (15 September 1992). Hyman's Comparative Vertebrate Anatomy. University of Chicago Press. ISBN   978-0-226-87013-7.
  4. 1 2 Austin CR (1984). "Evolution of the copulatory apparatus". Bolletino di Zoologia. 51 (1–2): 249–269. doi: 10.1080/11250008409439463 .
  5. 1 2 Romer AS, Parsons TS (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 396–399. ISBN   978-0-03-910284-5.
  6. ↑ Dusenbery, David B. (2009). Living at Micro Scale: The Unexpected Physics of Being Small. Harvard University Press. p. 326. ISBN   978-0-674-06021-0.
  7. ↑ Smith, Robert L. (2012-12-02). Sperm Competition and the Evolution of Animal Mating systems. Elsevier. pp. 7–8. ISBN   978-0-323-14313-4.
  8. ↑ Sawada, Hitoshi; Inoue, Naokazu; Iwano, Megumi (2014-02-07). Sexual Reproduction in Animals and Plants. Springer. pp. 97–98. ISBN   978-4-431-54589-7.
  9. ↑ Reichard UH (2002). "Monogamy—A variable relationship" (PDF). Max Planck Research. 3: 62–7. Archived from the original (PDF) on 14 May 2011. Retrieved 24 April 2013.
  10. ↑ Lipton JE, Barash DP (2001). The Myth of Monogamy: Fidelity and Infidelity in Animals and People . San Francisco: W.H. Freeman and Company. ISBN   978-0-7167-4004-9.
  11. ↑ Morell V (September 1998). "A new look at monogamy". Science. 281 (5385): 1982–3. doi:10.1126/science.281.5385.1982. PMID   9767050. S2CID   31391458.
  12. ↑ Lombardi J (6 December 2012). Comparative Vertebrate Reproduction. Springer Science & Business Media. ISBN   978-1-4615-4937-6.
  13. ↑ Diamond J (1991). The Rise and Fall of the Third Chimpanzee. Radius. pp. 360 pages. ISBN   978-0091742683.
  14. ↑ Wedell N, Tregenza T, Simmons LW (July 2008). "Nuptial gifts fail to resolve a sexual conflict in an insect". BMC Evolutionary Biology. 8: 204. doi: 10.1186/1471-2148-8-204 . PMC   2491630 . PMID   18627603.
  15. ↑ Sozou PD, Seymour RM (September 2005). "Costly but worthless gifts facilitate courtship". Proceedings. Biological Sciences. 272 (1575): 1877–84. doi:10.1098/rspb.2005.3152. PMC   1559891 . PMID   16191592.
  16. ↑ Bergquist PR (1978). Sponges. London: Hutchinson. ISBN   9780520036581.
  17. ↑ Lodé T (2001). Les stratégies de reproduction des animaux[Reproduction Strategies in the Animal Kingdom] (in French). Paris: Dunod Sciences.
  18. ↑ Blackburn DG (January 2000). "Classification of the reproductive patterns of amniotes". Herpetological Monographs. 14: 371–7. doi:10.2307/1467051. JSTOR   1467051.
  19. ↑ Carrier JC, Musick JA, Heithaus MR, eds. (2012). Biology of Sharks and Their Relatives. CRC Press. pp. 296–301. ISBN   978-1439839249.
  20. 1 2 Yokoe M, Takayama-Watanabe E, Saito Y, Kutsuzawa M, Fujita K, Ochi H, et al. (2016-08-31). Klymkowsky M (ed.). "A Novel Cysteine Knot Protein for Enhancing Sperm Motility That Might Facilitate the Evolution of Internal Fertilization in Amphibians". PLOS ONE. 11 (8): e0160445. Bibcode:2016PLoSO..1160445Y. doi: 10.1371/journal.pone.0160445 . PMC   5007030 . PMID   27579691.
  21. ↑ Altig R, McDiarmid RW (December 2007). "Morphological diversity and evolution of egg and clutch structure in amphibians". Herpetological Monographs. 21 (1): 1–32. doi:10.1655/06-005.1. S2CID   55728625.
  22. ↑ "43.2A: External and Internal Fertilization". Biology LibreTexts. 2018-07-17. Retrieved 2020-11-09.
  23. 1 2 Wallen K, Zehr JL (February 2004). "Hormones and history: the evolution and development of primate female sexuality". Journal of Sex Research. 41 (1): 101–12. doi:10.1080/00224490409552218. PMC   1255935 . PMID   15216429.
  24. ↑ Parker, G. A. (1970). "Sperm Competition and Its Evolutionary Consequences in the Insects". Biological Reviews. 45 (4): 525–567. doi:10.1111/j.1469-185X.1970.tb01176.x. ISSN   1469-185X. S2CID   85156929.
  25. 1 2 3 Cotner, Sehoya; Wassenberg, Deena (2020). The Evolution and Biology of Sex.
  26. ↑ Engel, Kathrin M; Dzyuba, Viktoriya; Ninhaus-Silveira, Alexandre; Veríssimo-Silveira, Rosicleire; Dannenberger, Dirk; Schiller, Jürgen; Steinbach, Christoph; Dzyuba, Borys (February 2020). "Sperm Lipid Composition in Early Diverged Fish Species: Internal vs. External Mode of Fertilization". Biomolecules . 10 (2): 172. doi: 10.3390/biom10020172 . PMC   7072473 . PMID   31979037.
  27. ↑ Brennan, Patricia L. R.; Birkhead, Tim R.; Zyskowski, Kristof; Van Der Waag, Jessica; Prum, Richard O. (10 September 2008). "Independent evolutionary reductions of the phallus in basal birds". Journal of Avian Biology . 39 (5): 487–492. doi: 10.1111/j.0908-8857.2008.04610.x .
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