![Aphid-giving-birth](https://upload.wikimedia.org/wikipedia/commons/1/11/Aphid-giving-birth.jpg)
Thelytoky (from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
''thēlys'' "female" and ''tokos'' "birth") is a type of
parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...
in which females are produced from unfertilized eggs, as for example in
aphid
Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...
s. Thelytokous parthenogenesis is rare among animals and reported in about 1,500
species
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...
, about 1 in 1000 of described animal species, according to a 1984 study.
It is more common in
invertebrates
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordat ...
, like
arthropods, but it can occur in
vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with c ...
, including
salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...
s,
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
, and
reptiles such as some
whiptail lizards.
Thelytoky can occur by different mechanisms, each of which has a different impact on the level of
homozygosity
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
...
. It is found in several groups of
Hymenoptera, including
Apidae
Apidae is the largest family within the superfamily Apoidea, containing at least 5700 species of bees. The family includes some of the most commonly seen bees, including bumblebees and honey bees, but also includes stingless bees (also used for ...
,
Aphelinidae,
Cynipidae
Gall wasps, also incorrectly called gallflies, are hymenopterans of the family Cynipidae in the wasp superfamily Cynipoidea. Their common name comes from the galls they induce on plants for larval development. About 1,300 species of this gener ...
,
Formicidae,
Ichneumonidae
The Ichneumonidae, also known as the ichneumon wasps, Darwin wasps, or ichneumonids, are a family of parasitoid wasps of the insect order Hymenoptera. They are one of the most diverse groups within the Hymenoptera with roughly 25,000 species cur ...
, and
Tenthredinidae
Tenthredinidae is the largest family of sawflies, with well over 7,500 species worldwide, divided into 430 genera. Larvae are herbivores and typically feed on the foliage of trees and shrubs, with occasional exceptions that are leaf miners, stem ...
. It can be induced in Hymenoptera by the
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...
''
Wolbachia
''Wolbachia'' is a genus of intracellular bacteria that infects mainly arthropod species, including a high proportion of insects, and also some nematodes. It is one of the most common parasitic microbes, and is possibly the most common reproducti ...
'' and ''Cardinium''.
Arrhenotoky and thelytoky in Hymenoptera
Hymenoptera (
ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...
s,
bees,
wasp
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. ...
s, and
sawflies
Sawflies are the insects of the suborder Symphyta within the order Hymenoptera, alongside ants, bees, and wasps. The common name comes from the saw-like appearance of the ovipositor, which the females use to cut into the plants where they lay ...
) have a
haplodiploid sex-determination system
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.
Haplodiploidy determines the sex ...
. They produce haploid males from unfertilized eggs (
arrhenotoky
Arrhenotoky (from Greek -τόκος ''-tókos'' "birth of -" + ἄρρην ''árrhēn'' "male person"), also known as arrhenotokous parthenogenesis, is a form of parthenogenesis in which unfertilized eggs develop into males. In most cases, parthe ...
), a form of
parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...
. However, in a few social hymenopterans,
queen
Queen or QUEEN may refer to:
Monarchy
* Queen regnant, a female monarch of a Kingdom
** List of queens regnant
* Queen consort, the wife of a reigning king
* Queen dowager, the widow of a king
* Queen mother, a queen dowager who is the mother ...
s or workers are capable of producing diploid female offspring by thelytoky.
The daughters produced may or may not be complete clones of their mother depending on the type of parthenogenesis that takes place.
[ The offspring can develop into either queens or workers. Examples of such species include the Cape bee, '']Apis mellifera capensis
The Cape honey bee or Cape bee (''Apis mellifera capensis'') is a southern South African subspecies of the western honey bee. They play a major role in South African agriculture and the economy of the Western Cape by pollinating crops and produc ...
'', ''Mycocepurus smithii
''Mycocepurus smithii'' is a species of fungus-growing ant from Latin America. This species is widely distributed geographically and can be found from Mexico in the north to Argentina in the south, as well as on some Caribbean Islands. It live ...
'' and clonal raider ant, ''Ooceraea biroi
''Ooceraea biroi'', the clonal raider ant, is a queenless clonal ant in the genus ''Ooceraea'' (recently transferred from the genus '' Cerapachys''). Native to the Asian mainland, this species has become invasive on tropical and subtropical islan ...
''.
Automixis
Automixis is a form of thelytoky. In automictic parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...
, meiosis
Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately r ...
takes place and diploidy is restored by fusion of first division non-sister nuclei (central fusion) or the second division sister nuclei (terminal fusion). (see diagram).
With central fusion
Automixis with central fusion tends to maintain heterozygosity in the passage of the genome from mother to daughter. This form of automixis has been observed in several ant species including the desert ant ''Cataglyphis cursor
''Cataglyphis cursor'' is a species of ant in the genus ''Cataglyphis''. Described in 1846, it is known only from the Mediterranean parts of France.
Reproduction
Parthenogenesis is a natural form of reproduction in which growth and development ...
'', the clonal raider ant ''Cerapachys biroi
''Ooceraea biroi'', the clonal raider ant, is a queenless clonal ant in the genus ''Ooceraea'' (recently transferred from the genus ''Cerapachys''). Native to the Asian mainland, this species has become invasive on tropical and subtropical islan ...
'', the predaceous ant ''Platythyrea punctata
''Platythyrea punctata'' is a species of ant in the family Formicidae.
References
Further reading
*
Ponerinae
Articles created by Qbugbot
Insects described in 1858
{{ponerinae-stub ...
'', and the electric ant (little fire ant) ''Wasmannia auropunctata
The little fire ant (''Wasmannia auropunctata''), also known as the electric ant, is a small (approx long), light to golden brown (ginger) social ant native to Central and South America, now spread to parts of Africa (including Gabon and Camer ...
''. Automixis with central fusion also occurs in the Cape honey bee ''Apis mellifera capensis
The Cape honey bee or Cape bee (''Apis mellifera capensis'') is a southern South African subspecies of the western honey bee. They play a major role in South African agriculture and the economy of the Western Cape by pollinating crops and produc ...
'', the brine shrimp ''Artemia parthenogenetica'', and the termite ''Embiratermes neotenicus''.
Oocyte
An oocyte (, ), oöcyte, or ovocyte is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in a female fetus in the ovary during female gametogenesis. The femal ...
s that undergo automixis with central fusion often display a reduced rate of crossover recombination. A low rate of recombination in automictic oocytes favors maintenance of heterozygosity
Zygosity (the noun, zygote, is from the Greek "yoked," from "yoke") () is the degree to which both copies of a chromosome or gene have the same genetic sequence. In other words, it is the degree of similarity of the alleles in an organism.
Mo ...
, and only a slow transition from heterozygosity to homozygosity over successive generations. This allows avoidance of immediate inbreeding depression
Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. ...
. Species that display central fusion with reduced recombination include the ants ''P. punctata'' and ''W. auropunctata'', the brine shrimp ''A. parthenogenetica'', and the honey bee ''A. m. capensis''. In ''A. m. capensis'', the recombination rate during the meiosis associated with thelytokous parthenogenesis is reduced by more than 10-fold. In ''W. auropunctata'' the reduction is 45-fold.
Single queen colonies of the narrow headed ant ''Formica exsecta
''Formica exsecta'' (the narrow-headed ant or excised wood ant) is a species of ant found from Western Europe to Asia.
A rare formicine ant with a deeply excised head, ''F. exsecta'' forms small mounds up to around a foot in height consisting ...
'' provide an illustrative example of the possible deleterious effects of increased homozygosity. In this ant the level of queen homozygosity is negatively associated with colony age. Reduced colony survival appears to be due to decreased queen lifespan resulting from queen homozygosity and expression of deleterious recessive mutations (inbreeding depression
Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. ...
).
With terminal fusion
Automixis with terminal fusion tends to promote homozygosity in the passage of the genome from mother to daughter. This form of automixis has been observed in the water flea ''Daphnia magna
''Daphnia magna'' is a small planktonic crustacean (adult length 1.5–5.0 mm) that belongs to the subclass Phyllopoda.
Description
''D. magna'' is a typical water flea of the genus ''Daphnia''. The females reach up to 5 mm in size, ...
'' and the Colombian rainbow boa constrictor '' Epicrates maurus''. Parthenogenesis in ''E. maurus'' is only the third genetically confirmed case of consecutive virgin births of viable offspring from a single female within any vertebrate lineage. However, survival of offspring over two successive litters was poor, suggesting that automixis with terminal fusion leads to homozygosity and expression of deleterious recessive allele
In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...
s (inbreeding depression
Inbreeding depression is the reduced biological fitness which has the potential to result from inbreeding (the breeding of related individuals). Biological fitness refers to an organism's ability to survive and perpetuate its genetic material. ...
).
See also
* Autotoky Autotoky is uniparental reproduction by self-fertilization or by parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, labe ...
* Epitoky
Epitoky is a process that occurs in many species of polychaete marine worms wherein a sexually immature worm (the atoke) is modified or transformed into a sexually mature worm (the epitoke). Epitokes are pelagic morphs capable of sexual reproduc ...
* Arrhenotoky
Arrhenotoky (from Greek -τόκος ''-tókos'' "birth of -" + ἄρρην ''árrhēn'' "male person"), also known as arrhenotokous parthenogenesis, is a form of parthenogenesis in which unfertilized eggs develop into males. In most cases, parthe ...
References
{{Eusociality
Beekeeping
Insect reproduction
Asexual reproduction