Polyembryony

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Polyembryony is the phenomenon of two or more embryos developing 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 of budding and typical sexual reproduction. [2] Polyembryony can occur in humans, resulting in identical twins, though the process is random and at a low frequency. [1] Polyembryony occurs regularly in many species of vertebrates, invertebrates, and plants.

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Evolution of polyembryony

The 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

Armadillos are the most well studied vertebrate that undergoes polyembryony, with six species of armadillo in the genus Dasypus that are always polyembryonic. [7] The nine 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] Through recent genotype analysis and molecular data, it has been suggested that polyembryony happens in the entire order Cyclostomata. [8]

A colony of wasps Wasp colony.jpg
A colony of wasps

Invertebrates

A more striking example of the use of polyembryony as a competitive reproductive tool is found in the parasitoid Hymenoptera, family Encyrtidae. [9] 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. [9] These latter larvae patrol the host and kill any other parasitoids they find with the exception of their siblings, usually sisters. [9]

Obligately polyembryonic insects fall in two classes: Hymenoptera (certain wasps), and Strepsiptera. [10] From one egg, these insects can produce over thousands of offspring. [10] Polyembryonic wasps from the Hymenoptera group can be further subdivided into four families including Braconidae ( Macrocentrus ), Platygastridae ( Platygaster ), Encyrtidae ( Copidosoma ), and Dryinidae. [10]

Polyembryony also occurs in Bryozoa. [2] [8]

Plants

The term is also used in botany to describe the phenomenon of seedlings emerging from one embryo. Around 20 genera of gymnospores undergo polyembryony, termed "cleavage polyembryony," where the original zygote splits 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 in Pinus sylvestris to be programmed 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 through competition, and therefore the now dormant seed, while the other embryos are destroyed through PCD. [1]

The genus Citrus has a number of species that undergo polyembryony, where multiple nucellar-cell-derived embryos exist alongside sexually-derived embryos. [11] [12] Antonie van Leeuwenhoek first described polyembryony in 1719 when the seed in Citrus was observed to have two germinating embryos. [3] In Citrus, polyembryony is genetically controlled by a shared polyembryony locus among the species, determined by single-nucleotide polymorphism in 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

Related Research Articles

Asexual reproduction Reproduction without a sexual process

Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and bacteria. Many eukaryotic organisms including plants, animals, and fungi can also reproduce asexually. In vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited.

Hymenoptera Order of insects comprising sawflies, wasps, bees, and ants

Hymenoptera is a large order of insects, comprising the sawflies, wasps, bees, and ants. Over 150,000 living species of Hymenoptera have been described, in addition to over 2,000 extinct ones. Many of the species are parasitic. Females typically have a special ovipositor for inserting eggs into hosts or places that are otherwise inaccessible. This ovipositor is often modified into a stinger. The young develop through holometabolism —that is, they have a wormlike larval stage and an inactive pupal stage before they mature.

Apomixis Replacement of the normal sexual reproduction by asexual reproduction, without fertilization

In botany, apomixis is asexual reproduction without fertilization. Its etymology is Greek for "away from" + "mixing". This definition notably does not mention meiosis. Thus "normal asexual reproduction" of plants, such as propagation from cuttings or leaves, has never been considered to be apomixis, but replacement of the seed by a plantlet or replacement of the flower by bulbils were categorized as types of apomixis. Apomictically produced offspring are genetically identical to the parent plant.

Chalcid wasp Superfamily of wasps

Chalcid wasps are insects within the superfamily Chalcidoidea, part of the order Hymenoptera. The superfamily contains some 22,500 known species, and an estimated total diversity of more than 500,000 species, meaning the vast majority have yet to be discovered and described. The name "chalcid" is often confused with the name "chalcidid", though the latter refers strictly to one constituent family, the Chalcididae, rather than the superfamily as a whole; accordingly, most recent publications (e.g.,) use the name "chalcidoid" when referring to members of the superfamily.

Parasitoid Organism that lives with host and kills it

In evolutionary ecology, a parasitoid is an organism that lives in close association with its host at the host's expense, eventually resulting in the death of the host. Parasitoidism is one of six major evolutionary strategies within parasitism, distinguished by the fatal prognosis for the host, which makes the strategy close to predation.

Apocrita Suborder of insects containing wasps, bees, and ants

Apocrita is a suborder of insects in the order Hymenoptera. It includes wasps, bees, and ants, and consists of many families. It contains the most advanced hymenopterans and is distinguished from Symphyta by the narrow "waist" (petiole) formed between the first two segments of the actual abdomen; the first abdominal segment is fused to the thorax, and is called the propodeum. Therefore, it is general practice, when discussing the body of an apocritan in a technical sense, to refer to the mesosoma and metasoma rather than the "thorax" and "abdomen", respectively. The evolution of a constricted waist was an important adaption for the parasitoid lifestyle of the ancestral apocritan, allowing more maneuverability of the female's ovipositor. The ovipositor either extends freely or is retracted, and may be developed into a stinger for both defense and paralyzing prey. Larvae are legless and blind, and either feed inside a host or in a nest cell provisioned by their mothers.

In biology, polyspermy describes the fertilization of an egg by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy, on the other hand, contains three or more copies of each chromosome—one from the egg and one each from multiple sperm. Usually, the result is an unviable zygote. This may occur because sperm are too efficient at reaching and fertilizing eggs due to the selective pressures of sperm competition. Such a situation is often deleterious to the female: in other words, the male–male competition among sperm spills over to create sexual conflict.

Haplodiploidy Biological system where sex is determined by the number of sets of chromosomes

Haplodiploidy is a sex-determination system in which males develop from unfertilized eggs and are haploid, and females develop from fertilized eggs and are diploid. Haplodiploidy is sometimes called arrhenotoky.

Parasitoid wasp Group of wasps

Parasitoid wasps are a large group of hymenopteran superfamilies, with all but the wood wasps (Orussoidea) being in the wasp-waisted Apocrita. As parasitoids, they lay their eggs on or in the bodies of other arthropods, sooner or later causing the death of these hosts. Different species specialise in hosts from different insect orders, most often Lepidoptera, though some select beetles, flies, or bugs; the spider wasps (Pompilidae) exclusively attack spiders.

Encyrtidae Family of wasps

Encyrtidae is a large family of parasitic wasps, with some 3710 described species in about 455 genera. The larvae of the majority are primary parasitoids on Hemiptera, though other hosts are attacked, and details of the life history can be variable. They are found throughout the world in virtually all habitats, and are extremely important as biological control agents. They may also present as an ecological threat to the population of some species. For example, the endangered Papilio homerus butterfly is parasitized at a rate of 77%, making them the main contributor to egg mortality in this butterfly species.

Nucellar embryony

Nucellar embryony is a form of seed reproduction that occurs in certain plant species, including many citrus varieties. Nucellar embryony is a type of apomixis, where eventually nucellar embryos from the nucellus tissue of the ovule are formed, independent of meiosis and sexual reproduction. During the development of seeds in plants that possess this genetic trait, the nucellus tissue which surrounds the megagametophyte can produce nucellar cells, also termed initial cells. These additional embryos (polyembryony) are genetically identical to the parent plant, rendering them as clones. By contrast, zygotic seedlings are sexually produced and inherit genetic material from both parents. Most angiosperms reproduce sexually through double fertilization. Different from nucellar embryony, double fertilization occurs via the syngamy of sperm and egg cells, producing a triploid endosperm and a diploid zygotic embryo. In nucellar embryony, embryos are formed asexually from the nucellus tissue. Zygotic and nucellar embryos can occur in the same seed (monoembryony), and a zygotic embryo can divide to produce multiple embryos. The nucellar embryonic initial cells form, divide, and expand. Once the zygotic embryo becomes dominant, the initial cells stop dividing and expanding. Following this stage, the zygotic embryo continues to develop and the initial cells continue to develop as well, forming nucellar embryos. The nucellar embryos generally end up outcompeting the zygotic embryo, rending the zygotic embryo dormant. The polyembryonic seed is then formed by the many adventitious embryos within the ovule. The nucellar embryos produced via apomixis inherit its mother’s genetics, making them desirable for citrus propagation, research, and breeding.

Parthenogenesis Asexual reproduction without fertilization

Parthenogenesis is a natural form of asexual reproduction in which growth and development of embryos occur without fertilization by sperm. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants parthenogenesis is a component process of apomixis.

<i>Nasonia vitripennis</i>

Nasonia vitripennis is one of four known species under the genus Nasonia - small parasitoid wasps that afflict the larvae of parasitic carrion flies such as blowflies and flesh flies, which themselves are parasitic toward nestling birds. It is the best known and most widely studied of the parasitoid wasps, and their study forms a vital part of the information used to describe the order Hymenoptera, along with information from bees and ants. This parasitoid behaviour makes the wasps an interest for the development of biopesticide and biological systems for controlling unwanted insects.

Wasp Members of the order Hymenoptera which are not ants nor bees

A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. The wasps do not constitute a clade, a complete natural group with a single ancestor, as bees and ants are deeply nested within the wasps, having evolved from wasp ancestors. Wasps that are members of the clade Aculeata can sting their prey.

<i>Copidosoma</i> Genus of wasps

Copidosoma is a genus of chalcid wasps, which are parasitoids of Lepidoptera. The wasps are polyembryonic, depositing one or two eggs into their host which then develop into multiple offspring and have a soldier caste and a reproductive caste.

<i>Copidosoma floridanum</i> Species of wasp

Copidosoma floridanum is a species of wasp in the family Encyrtidae which is primarily a parasitoid of moths in the subfamily Plusiinae. It has the largest recorded brood of any parasitoidal insect, at 3,055 individuals. The life cycle begins when a female oviposits into the eggs of a suitable host species, laying one or two eggs per host. Each egg divides repeatedly and develops into a brood of multiple individuals, a phenomenon called polyembryony. The larvae grow inside their host, breaking free at the end of the host's own larval stage.

Muscidifurax uniraptor is a species of wasp in the family Pteromalidae. The species does not currently have a common name. M. uniraptor is a pupal parasitoid of synanthropic filth-breeding Diptera and is a natural enemy of the housefly Musca domestica and the stable fly Stomoxys calcitrans.

<i>Diachasmimorpha longicaudata</i> Species of wasp

Diachasmimorpha longicaudata is a solitary species of parasitoid wasp and an endoparasitoid of tephritid fruit fly larvae. D. longicaudata is native to many countries in Southeast Asia and subtropical regions and has also been introduced to many other countries as a biological control agent. It is now considered the most extensively used parasitoid for biocontrol of fruit flies in both the southern portion of the United States and Latin America. D. longicaudata is especially useful for agricultural purposes in the control of fruit flies as it is easily mass-reared and has the ability to infect a variety of hosts within the genus Bactrocera. A negative factor in its use as a biocontrol agent is that it is known to oviposit in grapefruit in the state of Florida. This has resulted in quarantines on grapefruit shipped internationally as well as domestically. Research is ongoing to determine whether D. longicaudata is actually a single species, or if it contains multiple species. It is likely multiple biological species separated by both reproductive isolation and morphological characteristics such as wing geometry.

<i>Ooencyrtus</i> Genus of wasps

Ooencyrtus is a genus of chalcid wasp. William Harris Ashmead named and circumscribed the genus in 1900.

<i>Ooencyrtus kuvanae</i> Species of chalcid wasp

Ooencyrtus kuvanae is a species of chalcid wasp. It was introduced to North America in 1908 to control Lymantria moths. In North America, it has become an active parasitoid of the invasive spotted lanternfly.

References

  1. 1 2 3 4 5 6 7 Filonva, 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 . PMID   12232793.
  2. 1 2 3 4 5 Craig, 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. doi:10.1023/A:1018443714917. ISSN   0269-7653. S2CID   5556785.
  3. 1 2 3 Batygina, T. B.; Vinogradova, G. Iu (2007-05-01). "[Phenomenon of polyembryony. Genetic heterogeneity of seeds]". Ontogenez. 38 (3): 166–191. ISSN   0475-1450. PMID   17621974.
  4. 1 2 Segoli, 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.
  5. ↑
  6. ↑ 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.
  7. 1 2 Loughry, 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. JSTOR   27857027.
  8. 1 2 Jenkins, 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 . ISSN   1932-6203. PMC   5240946 . PMID   28095467.
  9. 1 2 3 E., Beckage, Nancy (1997-01-01). Parasites and pathogens : effects on host hormones and behavior. Chapman & Hall. ISBN   978-0412074011. OCLC   875319486.
  10. 1 2 3 Strand, Michael (2009). Encyclopedia of Insects (2nd ed.). Oxford, UK: Elsevier.
  11. 1 2 Nakano, 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. doi:10.1016/j.plantsci.2011.08.002. ISSN   1873-2259. PMID   22195586.
  12. 1 2 3 Kishore, 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. doi:10.1016/j.scienta.2012.01.035.

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  1. ↑ Strand, Michael R.; Grbic, Miodrag (1997-01-01), Pedersen, Roger A.; Schatten, Gerald P. (eds.), "The Development and Evolution of Polyembryonic Insects", Current Topics in Developmental Biology, Academic Press, vol. 35, pp. 121–159, retrieved 2022-04-10
  2. ↑ Donnell, David M.; Corley, Laura S.; Chen, Gang; Strand, Michael R. (2004-07-06). "Caste determination in a polyembryonic wasp involves inheritance of germ cells". Proceedings of the National Academy of Sciences of the United States of America. 101 (27): 10095–10100. doi:10.1073/pnas.0403625101. ISSN   0027-8424. PMID   15226498.
  3. ↑ Strand, Michael R. (2009-01-01), Resh, Vincent H.; Cardé, Ring T. (eds.), "Chapter 208 - Polyembryony", Encyclopedia of Insects (Second Edition), San Diego: Academic Press, pp. 821–825, ISBN   978-0-12-374144-8 , retrieved 2022-04-10
  4. ↑
  5. ↑
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