Polyembryonyis the phenomenon of two or moreembryosdeveloping from a single fertilized egg.[1][2][3]Due to the embryos resulting from the same egg, the embryos are identical to one another, but are genetically diverse from the parents.[1][2]The genetic difference between the offspring and the parents, but the similarity among siblings, are significant distinctions between polyembryony and the process ofbuddingand typicalsexual reproduction.[2]Polyembryony can occur in humans, resulting inidentical twins,though the process is random and at a low frequency.[1]Polyembryony occurs regularly in many species ofvertebrates,invertebrates,andplants.
Evolution of polyembryony
editThe evolution of polyembryony and the potential evolutionary advantages that may entail have been studied. In parasitoid wasps, there are several hypotheses surrounding the evolutionary advantages of polyembryony, one of them being that it allows female wasps that are small in size to increase the number of potential offspring in comparison to wasps that are mono embryonic.[4]There are limitations to monoembryony, but with this method of development, multiple embryos can be derived from each of the individual eggs that are laid.[5][4]
The potential advantages of polyembryony in competing invasive plant species has been studied as well.[6]
Vertebrates
editArmadillosare the most well studied vertebrate that undergoes polyembryony, with six species of armadillo in the genusDasypusthat are always polyembryonic.[7]Thenine banded armadillo,for instance, always gives birth to four identical young. There are two conditions that are expected to promote the evolution of polyembryony: the mother does not know the environmental conditions of her offspring as in the case of parasitoids, or a constraint on reproduction.[2]It is thought that nine banded armadillos evolved to be polyembryonic because of the latter.[7]
Invertebrates
editA more striking example of the use of polyembryony as a competitive reproductive tool is found in the parasitoidHymenoptera,familyEncyrtidae.[8]The progeny of the splitting embryo develop into at least two forms, those that will develop into adults and those that become a type of soldier, called precocious larvae.[8]These latter larvae patrol the host and kill any other parasitoids they find with the exception of their siblings, usually sisters.[8]
Obligately polyembryonic insects fall in two classes: Hymenoptera (certain wasps), andStrepsiptera.[9]From one egg, these insects can produce over thousands of offspring.[9]Polyembryonic wasps from the Hymenoptera group can be further subdivided into four families includingBraconidae(Macrocentrus),Platygastridae(Platygaster),Encyrtidae(Copidosoma), andDryinidae.[9]
Polyembryony also occurs inBryozoa.[2][10]Through genotype analysis and molecular data, it has been suggested that polyembryony happens in the entire bryozoan orderCyclostomatida.[10]
Plants
editThe term is also used inbotanyto describe the phenomenon ofseedlingsemerging from one embryo. Around 20 genera ofgymnosporesundergo polyembryony, termed "cleavagepolyembryony, "where the originalzygotesplits into many identical embryos.[1][3]In some plant taxa, the many embryos of polyembryony eventually gives rise to only a single offspring.[1]The mechanism underlying the phenomenon of a resulting single (or in some cases a few) offspring is described inPinus sylvestristo beprogrammed cell death(PCD), which removes all but one embryo.[1]Originally, all embryos have equal opportunity to develop into full seeds, but during the early stages of development, one embryo becomes dominant throughcompetition,and therefore the nowdormantseed, while the other embryos are destroyed through PCD.[1]
The genusCitrushas a number of species that undergo polyembryony, where multiple nucellar-cell-derived embryos exist alongside sexually-derived embryos.[11][12]Antonie van Leeuwenhoekfirst described polyembryony in 1719 when the seed inCitruswas observed to have two germinating embryos.[3]InCitrus,polyembryony is genetically controlled by a shared polyembryony locus among the species, determined bysingle-nucleotide polymorphismin the genotypes sequenced.[11]The variation within the species of citrus is based on the amount of embryos that develop, the impact of the environment, and gene expression.[12]As with other species, due to the many embryos developing in close proximity, competition occurs, which can cause variation in seed success or vigor.[12]
See also
editReferences
edit- ^abcdefgFilonva, L. H.; von Arnold, S.; Daniel, G.; Bozhkov, P. V. (2002)."Programmed cell death eliminates all but one embryo in a polyembryonic plant seed".Nature.9(10): 1057–1062.doi:10.1038/sj.cdd.4401068.PMID12232793.
- ^abcdeCraig, Sean F.; Slobodkin, Lawrence B.; Wray, Gregory A.; Biermann, Christiane H. (1997-03-01). "The 'paradox' of polyembryony: A review of the cases and a hypothesis for its evolution".Evolutionary Ecology.11(2): 127–143.Bibcode:1997EvEco..11..127C.doi:10.1023/A:1018443714917.ISSN0269-7653.S2CID5556785.
- ^abcBatygina, T. B.; Vinogradova, G. Iu (2007-05-01). "[Phenomenon of polyembryony. Genetic heterogeneity of seeds]".Ontogenez.38(3): 166–191.ISSN0475-1450.PMID17621974.
- ^abSegoli, M.; Harari, A. R.; Rosenheim, J. A.; Bouskila, A.; Keasar, T. (September 2010)."REVIEW: The evolution of polyembryony in parasitoid wasps: The evolution of polyembryony".Journal of Evolutionary Biology.23(9): 1807–1819.doi:10.1111/j.1420-9101.2010.02049.x.PMID20629853.S2CID22573370.
- ^Strand, Michael R. (2009-01-01),"Chapter 208 - Polyembryony",in Resh, Vincent H.; Cardé, Ring T. (eds.),Encyclopedia of Insects (Second Edition),San Diego: Academic Press, pp. 821–825,ISBN978-0-12-374144-8,retrieved2022-04-10
- ^Blanchard, Megan L.; Barney, Jacob N.; Averill, Kristine M.; Mohler, Charles L.; DiTommaso, Antonio (February 2010)."Does polyembryony confer a competitive advantage to the invasive perennial vine Vincetoxicum rossicum (Apocynaceae)?".American Journal of Botany.97(2): 251–260.doi:10.3732/ajb.0900232.PMID21622385.
- ^abLoughry, W. J.; Prodöhl, Paulo A.; McDonough, Colleen M.; Avise, John C. (1 January 1998). "Polyembryony in Armadillos: An unusual feature of the female nine-banded armadillo's reproductive tract may explain why her litters consist of four genetically identical offspring".American Scientist.86(3): 274–279.doi:10.1511/1998.25.824.JSTOR27857027.
- ^abcE., Beckage, Nancy (1997-01-01).Parasites and pathogens: effects on host hormones and behavior.Chapman & Hall.ISBN978-0412074011.OCLC875319486.
{{cite book}}
:CS1 maint: multiple names: authors list (link) - ^abcStrand, Michael (2009).Encyclopedia of Insects(2nd ed.). Oxford, UK: Elsevier.
- ^abJenkins, Helen L.; Waeschenbach, Andrea; Okamura, Beth; Hughes, Roger N.; Bishop, John D. D. (2017-01-17)."Phylogenetically Widespread Polyembryony in Cyclostome Bryozoans and the Protracted Asynchronous Release of Clonal Brood-Mates".PLOS ONE.12(1): e0170010.Bibcode:2017PLoSO..1270010J.doi:10.1371/journal.pone.0170010.ISSN1932-6203.PMC5240946.PMID28095467.
- ^abNakano, Michiharu; Shimada, Takehiko; Endo, Tomoko; Fujii, Hiroshi; Nesumi, Hirohisa; Kita, Masayuki; Ebina, Masumi; Shimizu, Tokurou; Omura, Mitsuo (2012-02-01). "Characterization of genomic sequence showing strong association with polyembryony among diverse Citrus species and cultivars, and its synteny with Vitis and Populus".Plant Science.183:131–142.Bibcode:2012PlnSc.183..131N.doi:10.1016/j.plantsci.2011.08.002.ISSN1873-2259.PMID22195586.
- ^abcKishore, Kundan; N., Monika; D., Rinchen; Lepcha, Boniface; Pandey, Brijesh (2012-05-01). "Polyembryony and seedling emergence traits in apomictic citrus".Scientia Horticulturae.138:101–107.Bibcode:2012ScHor.138..101K.doi:10.1016/j.scienta.2012.01.035.
External links
edit- Juan Manuel Alvarez A. (15 April 1997)."Chapter 26 — Largest Parasitoid Brood".Book of Insect Records.University of Florida.
- J. Bronté Gatenby (1918)."Memoirs: Polyembryony in Parasitic Hymenoptera: A Review".Quarterly Journal of Microscopical Science.s2-63: 175–196.
- J. Bronté Gatenby (1918)."The Segregation of the Germ-cells inTrichogramma evanescens".Quarterly Journal of Microscopical Science.s2-63: 161–174.
- Craig, S.F.; Slobodkin, L.B.; Wray, G. (1997). "The 'Paradox' of Polyembryony: A review of the cases and a hypothesis for its evolution".Evolutionary Ecology.11(2): 127–143.Bibcode:1997EvEco..11..127C.doi:10.1023/A:1018443714917.S2CID5556785.