External fertilization

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.[1] 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.[2]

In animals, external fertilization typically occurs in water or a moist area to facilitate the movement of sperm to the egg.[3] The release of eggs and sperm into the water is known as spawning.[4] In motile species, spawning females often travel to a suitable location to release their eggs. However, sessile species are less able to move to spawning locations and must release gametes locally.[4] Among vertebrates, external fertilization is most common in amphibians and fish.[5] Invertebrates utilizing external fertilization are mostly benthic, sessile, or both, including animals such as coral, sea anemones, and tube-dwelling polychaetes.[3] Benthic marine plants also reproduce through external fertilization.[3] Environmental factors and timing are key challenges to the success of external fertilization. While in the water, the male and female must both release gametes at similar times in order to fertilize the egg.[3] Gametes spawned into the water may also be washed away, eaten, or damaged by external factors.

  1. ^ Alonzo, Suzanne H.; Stiver, Kelly A.; Marsh-Rollo, Susan E. (2016). "Ovarian fluid allows directional cryptic female choice despite external fertilization". Nature Communications. 7: 12452. Bibcode:2016NatCo...712452A. doi:10.1038/ncomms12452. PMC 4990696. PMID 27529581.
  2. ^ Costa, Wilson J.E.M.; Amorim, Pedro F.; Mattos, José Leonardo O. (2016). "Molecular phylogeny and evolution of internal fertilization in South American seasonal cynopoeciline killifishes". Molecular Phylogenetics and Evolution. 95: 94–9. Bibcode:2016MolPE..95...94C. doi:10.1016/j.ympev.2015.11.011. PMID 26642825.
  3. ^ a b c d Denny, Mark W.; Shibata, Mark F. (1989). "Consequences of Surf-Zone Turbulence for Settlement and External Fertilization". The American Naturalist. 134 (6): 859–89. doi:10.1086/285018. JSTOR 2462013. S2CID 84201209.
  4. ^ a b Robalo, Joana I.; Castilho, Rita; Francisco, Sara M.; Almada, Frederico; Knutsen, Halvor; Jorde, Per E.; Pereira, Ana M.; Almada, Vitor C. (2012). "Northern refugia and recent expansion in the North Sea: The case of the wrasse Symphodus melops (Linnaeus, 1758)". Ecology and Evolution. 2 (1): 153–64. Bibcode:2012EcoEv...2..153R. doi:10.1002/ece3.77. PMC 3297185. PMID 22408733.
  5. ^ Kondo, Yasuyuki; Kashiwagi, Akihiko (2004). "Experimentally Induced Autotetraploidy and Allotetraploidy in Two Japanese Pond Frogs". Journal of Herpetology. 38 (3): 381–92. doi:10.1670/160-02A. JSTOR 1565777. S2CID 86149061.