93-406: See text Eriococcidae is a family of scale insects in the order Hemiptera . They are commonly known as felt scales or eriococcids . As of 2023, there are 109 genera and 681 species. Each species is usually specific to a different plant host, or closely related group of hosts. Recent research using ribosomal DNA has shown that the family Eriococcidae is not a single monophyletic group but
186-445: A tripartite symbiosis . Some ants and scale insects have a mutualistic relationship; the ants feed on the honeydew and in return protect the scales. On a tulip tree , ants have been observed building a papery tent over the scales. In other instances, scale insects are carried inside the ant's nest; the ant Acropyga exsanguis takes this to an extreme by transporting a fertilised female mealybug with it on its nuptial flight, so that
279-538: A complex life cycle. Species in this genus can produce separate male galls that are induced on existing female galls. Some species are tree pests in North America, including: European elm scale, azalea bark scale, oak eriococcin, crape myrtle bark scale, beech scale. Scale insect See text Scale insects are small insects of the order Hemiptera , suborder Sternorrhyncha . Of dramatically variable appearance and extreme sexual dimorphism , they comprise
372-445: A consequence, research on human parthenogenesis is focused on the production of embryonic stem cells for use in medical treatment, not as a reproductive strategy. In 2022, researchers reported that they have achieved parthenogenesis in mice for viable offspring born from unfertilized eggs, addressing the problems of genomic imprinting by "targeted DNA methylation rewriting of seven imprinting control regions". In 1955, Helen Spurway ,
465-492: A crawler can crawl before it needs to shed its skin and start feeding. There are various strategies for dealing with deciduous trees. On these, males often feed on the leaves, usually beside the veins, while females select the twigs. Where there are several generations in the year, there may be a general retreat onto the twigs as fall approaches. On branches, the underside is usually preferred as giving protection against predation and adverse weather. The solenopsis mealybug feeds on
558-427: A drone father, while the production of further drones (males) depends on the queen (and occasionally workers) producing unfertilized eggs. This means that females (workers and queens) are always diploid, while males (drones) are always haploid, and produced parthenogenetically. Facultative parthenogenesis occurs when a female can produce offspring either sexually or via asexual reproduction. Facultative parthenogenesis
651-423: A fertile, viable female in a few, e.g., boas ). ZW offspring are produced by endoreplication before meiosis or by central fusion. ZZ and WW offspring occur either by terminal fusion or by endomitosis in the egg cell. In polyploid obligate parthenogens, like the whiptail lizard, all the offspring are female. In many hymenopteran insects such as honeybees, female eggs are produced sexually, using sperm from
744-419: A few vertebrates , such as some fish , amphibians , reptiles , and birds . This type of reproduction has been induced artificially in a number of animal species that naturally reproduce through sex, including fish, amphibians, and mice. Some species reproduce exclusively by parthenogenesis (such as the bdelloid rotifers ), while others can switch between sexual reproduction and parthenogenesis. This
837-620: A full set (two sets of genes) provided solely by the mother. Thus, a male is not needed to provide sperm to fertilize the egg. This form of asexual reproduction is thought in some cases to be a serious threat to biodiversity for the subsequent lack of gene variation and potentially decreased fitness of the offspring. Some invertebrate species that feature (partial) sexual reproduction in their native range are found to reproduce solely by parthenogenesis in areas to which they have been introduced . Relying solely on parthenogenetic reproduction has several advantages for an invasive species : it obviates
930-494: A geneticist specializing in the reproductive biology of the guppy ( Lebistes reticulatus ), claimed that parthenogenesis may occur (though very rarely) in humans, leading to so-called "virgin births". This created some sensation among her colleagues and the lay public alike. Sometimes an embryo may begin to divide without fertilization, but it cannot fully develop on its own; so while it may create some skin and nerve cells, it cannot create others (such as skeletal muscle) and becomes
1023-482: A herd of scale insects inside the hollow stems of a Barteria tree; the scale insects feed on the sap and the ants, while benefiting from the honeydew, drive away other herbivorous insects from the tree as well as preventing vines from smothering it. Scale insects have various natural enemies, and research in this field is largely directed at the species that are crop pests. Entomopathogenic fungi can attack suitable scales and completely overgrow them. The identity of
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#17328517507401116-617: A male and a female produces only females. The reason for this is the non-random segregation of the sex chromosomes 'X' and 'O' during spermatogenesis . Facultative parthenogenesis is often used to describe cases of spontaneous parthenogenesis in normally sexual animals. For example, many cases of spontaneous parthenogenesis in sharks , some snakes , Komodo dragons , and a variety of domesticated birds were widely attributed to facultative parthenogenesis. These cases are examples of spontaneous parthenogenesis. The occurrence of such asexually produced eggs in sexual animals can be explained by
1209-414: A male is absent from the habitat or if it is unable to produce viable offspring. However, California condors and the tropical lizard Lepidophyma smithii both can produce parthenogenic offspring in the presence of males, indicating that facultative parthenogenesis may be more common than previously thought and is not simply a response to a lack of males. In aphids , a generation sexually conceived by
1302-505: A male is present and available for a female to breed with. In times of stress, offspring produced by sexual reproduction may be fitter as they have new, possibly beneficial gene combinations. In addition, sexual reproduction provides the benefit of meiotic recombination between non- sister chromosomes , a process associated with repair of DNA double-strand breaks and other DNA damages that may be induced by stressful conditions. Many taxa with heterogony have within them species that have lost
1395-424: A meiotic error, leading to eggs produced via automixis . Obligate parthenogenesis is the process in which organisms exclusively reproduce through asexual means. Many species have transitioned to obligate parthenogenesis over evolutionary time. Well documented transitions to obligate parthenogenesis have been found in numerous metazoan taxa, albeit through highly diverse mechanisms. These transitions often occur as
1488-667: A million years. The success of those salamanders may be due to rare fertilization of eggs by males, introducing new material to the gene pool, which may result from perhaps only one mating out of a million. In addition, the Amazon molly is known to reproduce by gynogenesis. Hybridogenesis is a mode of reproduction of hybrids . Hybridogenetic hybrids (for example AB genome ), usually females, during gametogenesis exclude one of parental genomes (A) and produce gametes with unrecombined genome of second parental species (B), instead of containing mixed recombined parental genomes. First genome (A)
1581-662: A non-specific protein synthesis inhibitor, enhances parthenote development in swine presumably by continual inhibition of MPF/cyclin B. As meiosis proceeds, extrusion of the second polar is blocked by exposure to cytochalasin B. This treatment results in a diploid (2 maternal genomes) parthenote Parthenotes can be surgically transferred to a recipient oviduct for further development, but will succumb to developmental failure after ≈30 days of gestation. The swine parthenote placentae often appears hypo-vascular: see free image (Figure 1) in linked reference. Induced parthenogenesis in mice and monkeys often results in abnormal development. This
1674-439: A result of inbreeding or mutation within large populations. Some documented species, specifically salamanders and geckos, that rely on obligate parthenogenesis as their major method of reproduction. As such, there are over 80 species of unisex reptiles (mostly lizards but including a single snake species), amphibians and fishes in nature for which males are no longer a part of the reproductive process. A female produces an ovum with
1767-404: A short period of time until they find a suitable place to feed, then settle down. The mobile adult males move around to find females to mate with. Eriococcidae are herbivores, like other scale insects. They occur on various hosts including trees, shrubs and grasses, and on most plant parts. Many species produce galls , including Apiomorpha which feed on various species of eucalypt and have
1860-401: A sperm cell; this must have happened early in development, as self-activated eggs quickly lose their ability to be fertilized. The unfertilized cells eventually duplicated their DNA, boosting their chromosomes to 46. When the unfertilized cells hit a developmental block, the fertilized cells took over and developed that tissue. The boy had asymmetrical facial features and learning difficulties but
1953-606: A type of benign tumor called an ovarian teratoma . Spontaneous ovarian activation is not rare and has been known about since the 19th century. Some teratomas can even become primitive fetuses (fetiform teratoma) with imperfect heads, limbs and other structures, but are non-viable. In 1995, there was a reported case of partial human parthenogenesis; a boy was found to have some of his cells (such as white blood cells ) to be lacking in any genetic content from his father. Scientists believe that an unfertilized egg began to self-divide but then had some (but not all) of its cells fertilized by
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#17328517507402046-457: A wide geographic range and a diversity of plant hosts are more likely to be asexual. Large population size is hypothesized to protect an asexual population from becoming extinct, but nevertheless, parthenogenesis is uncommon among scale insects, with the most widespread generalist feeders reproducing sexually, the majority of these being pest species. Many species have the XX-XO system where the female
2139-420: Is diploid and homogametic while the male is heterogametic and missing a sex chromosome. In some Diaspididae and Pseudococcidae , both sexes are produced from fertilized eggs but during development males eliminate the paternal genome and this system called paternal genome elimination (PGE) is found in nearly 14 scale insect families. This elimination is achieved with several variations. The commonest (known as
2232-499: Is also true haplodiploidy with females born from fertilized eggs and males from unfertilized eggs. This is seen in the genus Icerya . In Parthenolecanium , males are born from unfertilized eggs but diploidy is briefly restored by fusion of haploid cleave nuclei and then one sex chromosome is lost through heterochromatinization. Females can reproduce parthenogenetically with six different variants based on whether males are entirely absent or not (obligate v. facultative parthenogenesis);
2325-506: Is an aggregation of several different groups. Some species that appear morphologically similar seem to be only distantly related while dissimilar species are sometimes more closely related. The type genus Eriococcus has been shown to be polyphyletic . Adult females of many felt scales produce a white, yellowish or gray membranous capsule or ovisac that encloses the pyriform (pear-shaped) body. The body itself varies in colour and may be pink, red or purple, green or brown. The posterior end of
2418-527: Is attractive to ants as well as acting as a substrate on which sooty mould can grow. The mould can reduce photosynthesis by the leaves and detracts from the appearance of ornamental plants. The scale's activities can result in stress for the plant, causing reduced growth and giving it a greater susceptibility to plant diseases. Scale insects in the genus Cryptostigma live inside the nests of neotropical ant species. Many tropical plants need ants to survive which in turn cultivate scale insects thus forming
2511-460: Is because in asexual reproduction a successful genotype can spread quickly without being modified by sex or wasting resources on male offspring who will not give birth. Some species can produce both sexually and through parthenogenesis, and offspring in the same clutch of a species of tropical lizard can be a mix of sexually produced offspring and parthenogenically produced offspring. In California condors, facultative parthenogenesis can occur even when
2604-480: Is because mammals have imprinted genetic regions, where either the maternal or the paternal chromosome is inactivated in the offspring for development to proceed normally. A mammal created by parthenogenesis would have double doses of maternally imprinted genes and lack paternally imprinted genes, leading to developmental abnormalities. It has been suggested that defects in placental folding or interdigitation are one cause of swine parthenote abortive development. As
2697-478: Is called facultative parthenogenesis (other terms are cyclical parthenogenesis, heterogamy or heterogony ). The switch between sexuality and parthenogenesis in such species may be triggered by the season ( aphid , some gall wasps ), or by a lack of males or by conditions that favour rapid population growth ( rotifers and cladocerans like Daphnia ). In these species asexual reproduction occurs either in summer (aphids) or as long as conditions are favourable. This
2790-444: Is extremely rare in nature, with only a few examples of animal taxa capable of facultative parthenogenesis. One of the best-known examples of taxa exhibiting facultative parthenogenesis are mayflies ; presumably, this is the default reproductive mode of all species in this insect order. Facultative parthenogenesis has generally been believed to be a response to a lack of a viable male. A female may undergo facultative parthenogenesis if
2883-508: Is known as the "mealybug destroyer" because both adults and larvae feed on mealybugs and some soft scales. Ants looking after their providers of honeydew tend to drive off predators, but the mealybug destroyer has outwitted the ants by developing cryptic camouflage, with their larvae mimicking scale larvae. Many scale species are serious crop pests and are particularly problematic for their ability to evade quarantine measures. In 1990, they caused around $ 5 billion of damage to crops in
Eriococcidae - Misplaced Pages Continue
2976-531: Is more complicated. In some cases, the offspring are haploid (e.g., male ants ). In other cases, collectively called automictic parthenogenesis , the ploidy is restored to diploidy by various means. This is because haploid individuals are not viable in most species. In automictic parthenogenesis, the offspring differ from one another and from their mother. They are called half clones of their mother. Automixis includes several reproductive mechanisms, some of which are parthenogenetic. Diploidy can be restored by
3069-495: Is present is due to crossing over. In the case of endomitosis after meiosis, the offspring is completely homozygous and has only half the mother's genetic material. This can result in parthenogenetic offspring being unique from each other and from their mother. In apomictic parthenogenesis, the offspring are clones of the mother and hence (except for aphids) are usually female. In the case of aphids, parthenogenetically produced males and females are clones of their mother except that
3162-438: Is restored by fertilization of these gametes with gametes from the first species (AA, sexual host, usually male). Hybridogenesis is not completely asexual, but hemiclonal: half the genome is passed to the next generation clonally , unrecombined, intact (B), other half sexually , recombined (A). This process continues, so that each generation is half (or hemi-) clonal on the mother's side and has half new genetic material from
3255-532: Is secreted as honeydew on which sooty mold tends to grow. The insects often have a mutualistic relationship with ants , which feed on the honeydew and protect them from predators . There are about 8,000 described species. The oldest fossils of the group date to the Late Jurassic , preserved in amber . They were already substantially diversified by the Early Cretaceous suggesting an earlier origin during
3348-467: Is very rare in insects, but several species of Icerya exhibit an unusual form. The adult possesses an ovotestis, consisting of both female and male reproductive tissue, and sperm is transmitted to the young for their future use. The fact that a new population can be founded by a single individual may have contributed to the success of the cottony cushion scale which has spread around the world. Female scale insects in more advanced families develop from
3441-531: The Cretaceous , the period in which angiosperms came to dominance among plants, with only a few groups species found on gymnosperms . They feed on a wide variety of plants but are unable to survive long away from their hosts. While some specialise on a single plant species (monophagous), and some on a single genus or plant family (oligophagous), others are less specialised and feed on several plant groups (polyphagous). The parasite biologist Robert Poulin notes that
3534-470: The HLA region of DNA. These stem cells are called HLA homozygous parthenogenetic human stem cells (hpSC-Hhom) and would allow derivatives of these cells to be implanted without immune rejection. With selection of oocyte donors according to HLA haplotype , it would be possible to generate a bank of cell lines whose tissue derivatives, collectively, could be MHC-matched with a significant number of individuals within
3627-543: The Triassic or Jurassic . Their closest relatives are the jumping plant lice , whiteflies , phylloxera bugs and aphids . The majority of female scale insects remain in one place as adults, with newly hatched nymphs, known as "crawlers", being the only mobile life stage, apart from the short-lived males. The reproductive strategies of many species include at least some amount of asexual reproduction by parthenogenesis . Some scale insects are serious commercial pests, notably
3720-754: The X0 sex-determination system have two X chromosomes and are female. In species that use the ZW sex-determination system , they have either two Z chromosomes (male) or two W chromosomes (mostly non-viable but rarely a female), or they could have one Z and one W chromosome (female). Parthenogenesis is a form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization . It occurs naturally in some plants, algae , invertebrate animal species (including nematodes , some tardigrades , water fleas , some scorpions , aphids , some mites, some bees , some Phasmatodea , and parasitic wasps ), and
3813-496: The boreal ensign scale ( Newsteadia floccosa ) inhabits plant litter . A Hawaiian mealybug Clavicoccus erinaceus that fed solely on the now critically endangered Abutilon sandwicense has gone extinct as has another species Phyllococcus oahuensis . Several other monophagous scale insects, especially those on islands, are threatened by coextinction due to threats faced by their host plants. Most scale insects are herbivores , feeding on phloem sap drawn directly from
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3906-415: The mice created by Tokyo scientists in 2004. Although Hwang deceived the world about being the first to create artificially cloned human embryos, he contributed a major breakthrough to stem cell research by creating human embryos using parthenogenesis. A form of asexual reproduction related to parthenogenesis is gynogenesis. Here, offspring are produced by the same mechanism as in parthenogenesis, but with
3999-702: The "Neococcoids". A cladogram showing the major families using this methodology is shown below. † Burmacoccidae † Kozariidae Matsucoccidae (pine bast scales) Ortheziidae (ensign scales) Margarodidae (ground pearls) Kuwaniidae Xylococcidae Coelostomidiidae Monophlebidae (cottony cushion scales) Pityococcidae Steingeliidae Phenacoleachiidae Putoidae (giant mealybugs) Pseudococcidae (mealybugs) Coccidae (soft scales) Kermesidae (kermes dye scales) Asterolecaniidae (pit scales) Kerriidae (lac scales) Parthenogenesis Parthenogenesis ( / ˌ p ɑːr θ ɪ n oʊ ˈ dʒ ɛ n ɪ s ɪ s , - θ ɪ n ə -/ ; from
4092-529: The Coccomorpha was estimated in a 2016 study based on molecular clock divergence time estimates, along with fossils being used for calibration. They suggested that the main scale insect lineages diverged before their angiosperm hosts, and suggested that the insects switched from feeding on gymnosperms once the angiosperms became common and widespread in the Cretaceous. They estimated that the Coccomorpha appeared at
4185-484: The Greek παρθένος , parthénos , 'virgin' + γένεσις , génesis , 'creation' ) is a natural form of asexual reproduction in which the embryo develops directly from an egg without need for fertilization . In animals , parthenogenesis means development of an embryo from an unfertilized egg cell . In plants , parthenogenesis is a component process of apomixis . In algae , parthenogenesis can mean
4278-505: The International Stem Cell Corporation of California announced that Elena Revazova had intentionally created human stem cells from unfertilized human eggs using parthenogenesis. The process may offer a way for creating stem cells genetically matched to a particular female to treat degenerative diseases. The same year, Revazova and ISCC published an article describing how to produce human stem cells that are homozygous in
4371-590: The Southern Hemisphere. Parthenogenesis does not apply to isogamous species. Parthenogenesis occurs naturally in aphids , Daphnia , rotifers , nematodes , and some other invertebrates, as well as in many plants. Among vertebrates , strict parthenogenesis is only known to occur in lizards, snakes, birds, and sharks. Fish, amphibians, and reptiles make use of various forms of gynogenesis and hybridogenesis (an incomplete form of parthenogenesis). The first all-female (unisexual) reproduction in vertebrates
4464-569: The United States. The waxy covering of many species of scale protects their adults effectively from contact insecticides , which are only effective against the first-instar nymph stage known as the crawler . However, scales can often be controlled using horticultural oils that suffocate them, systemic pesticides that poison the sap of the host plants, or by biological control agents such as tiny parasitoid wasps and ladybirds. Insecticidal soap may also be used against scales. One species,
4557-424: The case of pre-meiotic doubling, recombination, if it happens, occurs between identical sister chromatids. If terminal fusion (restitutional meiosis of anaphase II or the fusion of its products) occurs, a little over half the mother's genetic material is present in the offspring and the offspring are mostly homozygous. This is because at anaphase II the sister chromatids are separated and whatever heterozygosity
4650-402: The colour and the insect. The colour name " scarlet " is similarly derived from Arabic siklāt , denoting extremely expensive luxury silks dyed red using kermes. Some waxy scale species in the genera Ceroplastes and Ericerus produce materials such as Chinese wax , and several genera of lac scales produce shellac . The containing group of the scale insects was formerly treated as
4743-464: The cottony cushion scale ( Icerya purchasi ) on Citrus fruit trees; they are difficult to control as the scale and waxy covering protect them effectively from contact insecticides. Some species are used for biological control of pest plants such as the prickly pear, Opuntia . Others produce commercially valuable substances including carmine and kermes dyes, and shellac lacquer. The two red colour-names crimson and scarlet both derive from
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#17328517507404836-541: The cottony cushion scale, is a serious commercial pest on 65 families of woody plants, including Citrus fruits. It has spread worldwide from Australia. At the same time, some kinds of scale insects are themselves useful as biological control agents for pest plants, such as various species of cochineal insects that attack invasive species of prickly pear , which spread widely especially in Australia and Africa. Some types of scale insect are economically valuable for
4929-581: The development of an embryo from either an individual sperm or an individual egg. Parthenogenesis occurs naturally in some plants, algae , invertebrate animal species (including nematodes , some tardigrades , water fleas , some scorpions , aphids , some mites, some bees , some Phasmatodea , and parasitic wasps ), and a few vertebrates , such as some fish , amphibians , and reptiles . This type of reproduction has been induced artificially in animal species that naturally reproduce through sex, including fish, amphibians, and mice. Normal egg cells form in
5022-409: The doubling of the chromosomes without cell division before meiosis begins or after meiosis is completed. This is an endomitotic cycle. Diploidy can also be restored by fusion of the first two blastomeres , or by fusion of the meiotic products. The chromosomes may not separate at one of the two anaphases (restitutional meiosis)l; or the nuclei produced may fuse; or one of the polar bodies may fuse with
5115-490: The egg cell at some stage during its maturation. Some authors consider all forms of automixis sexual as they involve recombination. Many others classify the endomitotic variants as asexual and consider the resulting embryos parthenogenetic. Among these authors, the threshold for classifying automixis as a sexual process depends on when the products of anaphase I or of anaphase II are joined. The criterion for sexuality varies from all cases of restitutional meiosis, to those where
5208-402: The egg through a first instar (crawler) stage and a second instar stage before becoming adult. In more primitive families there is an additional instar stage. Males pass through a first and second instar stage, a pre-pupal and a pupal stage before adulthood (actually a pseudopupa, as only holometabolous insects have a true pupa). The first instars of most species of scale insects emerge from
5301-480: The egg with functional legs, and are informally called "crawlers". They immediately crawl around in search of a suitable spot to settle down and feed. In some species they delay settling down either until they are starving, or until they have been blown away by wind onto what presumably is another plant, where they may establish a new colony. There are many variations on such themes, such as scale insects that are associated with species of ants that act as herders and carry
5394-434: The families Margarodidae, Ortheziidae and Pseudococcidae are mobile and can move to other parts of the host plant or even adjoining plants, but the mobile period is limited to a short period between moults. Some of these overwinter in crevices in the bark or among plant litter, moving in spring to tender young growth. However, the majority of female scale insects are sedentary as adults. Their dispersal ability depends on how far
5487-461: The families were monophyletic except for the Eriococcidae . The Coccomorpha are division into two clades the "Archaeococcoids" and "Neococcoids". The archaeococcoid families have adult males with either compound eyes or a row of unicorneal eyes and have abdominal spiracles in the females. In neoccoids, the females have no abdominal spiracles. In the cladogram below the genus Pityococcus is moved to
5580-481: The father's side. This form of reproduction is seen in some live-bearing fish of the genus Poeciliopsis as well as in some of the Pelophylax spp. ("green frogs" or "waterfrogs"): Other examples where hybridogenesis is at least one of modes of reproduction include i.e. Parthenogenesis, in the form of reproduction from a single individual (typically a god), is common in mythology, religion, and folklore around
5673-582: The feeding behaviour of scale insects closely resembles that of ectoparasites , living on the outside of their host and feeding only on them, even if they have not traditionally been so described; in his view, those species that remain immobile on a single host and feed only on it behave as obligate ectoparasites. For example, cochineal species are restricted to cactus hosts, and the gall-inducing Apiomorpha are restricted to Eucalyptus . Some species have certain habitat requirements; some Ortheziidae occur in damp meadows, among mosses and in woodland soil, and
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#17328517507405766-515: The foliage of its host in summer and the roots in winter, and large numbers of scale species feed invisibly, year-round on roots. Scale insects show a very wide range of variations in the genetics of sex determination and the modes of reproduction. Besides sexual reproduction , a number of different forms of reproductive systems are employed, including asexual reproduction by parthenogenesis . In some species, sexual and asexual populations are found in different locations, and in general, species with
5859-467: The forewings are fully functional. This is unusual among insects; it most closely resembles the situation in the true flies , the Diptera. However, the Diptera and Hemiptera are not closely related, and do not closely resemble each other in morphology ; for example, the tail filaments of the Coccomorpha do not resemble anything in the morphology of flies. The hind ( metathoracic ) wings are reduced, commonly to
5952-401: The fusion of its products), the offspring get all to more than half of the mother's genetic material and heterozygosity is mostly preserved (if the mother has two alleles for a locus, it is likely that the offspring will get both). This is because in anaphase I the homologous chromosomes are separated. Heterozygosity is not completely preserved when crossing over occurs in central fusion. In
6045-456: The host is not always apparent as many fungi are host-specific, and may destroy all the scales of one species present on a leaf while not affecting another species. Fungi in the genus Septobasidium have a more complex, mutualistic relationship with scale insects. The fungus lives on trees where it forms a mat which overgrows the scales, reducing the growth of the individual parasitised scales and sometimes rendering them infertile, but protecting
6138-491: The human population. After an independent investigation, it was revealed that the discredited South Korean scientist Hwang Woo-Suk unknowingly produced the first human embryos resulting from parthenogenesis. Initially, Hwang claimed he and his team had extracted stem cells from cloned human embryos, a result later found to be fabricated. Further examination of the chromosomes of these cells show indicators of parthenogenesis in those extracted stem cells, similar to those found in
6231-850: The immature external morphology even when sexually mature, a condition known as neoteny . Adult females are pear-shaped, elliptical or circular, with no wings, and usually no constriction separating the head from the body. Segmentation of the body is indistinct, but may be indicated by the presence of marginal bristles. Legs are absent in the females of some families, and when present vary from single segment stubs to five-segmented limbs. Female scale insects have no compound eyes, but ocelli (simple eyes) are sometimes present in Margarodidae , Ortheziidae and Phenacoleachiidae . The family Beesoniidae lacks antennae , but other families possess antennae with from one to thirteen segments. The mouthparts are adapted for piercing and sucking. Adult males in contrast have
6324-630: The infraorder Coccomorpha which is considered a more convenient grouping than the superfamily Coccoidea due to taxonomic uncertainties. Adult females typically have soft bodies and no limbs, and are concealed underneath domed scales, extruding quantities of wax for protection. Some species are hermaphroditic, with a combined ovotestis instead of separate ovaries and testes. Males, in the species where they occur, have legs and sometimes wings, and resemble small flies. Scale insects are herbivores , piercing plant tissues with their mouthparts and remaining in one place, feeding on sap . The excess fluid they imbibe
6417-665: The lecanoid system) involved deactivation of the paternal genome and elimination at the time of sperm production in males, this is seen in Pseudococcidae, Kerriidae and some Eriococcidae . In the other variant or Comstockiella system, the somatic cells have the paternal genome untouched. A third variant found in Diaspididae involves the paternal genome being completely removed at an early stage making males haploid both in somatic and germ cells even though they are formed from diploids, i.e., from fertilized eggs. In addition to this there
6510-496: The males lack one of the X chromosomes (XO). When meiosis is involved, the sex of the offspring depends on the type of sex determination system and the type of apomixis. In species that use the XY sex-determination system , parthenogenetic offspring have two X chromosomes and are female. In species that use the ZW sex-determination system the offspring genotype may be one of ZW (female), ZZ (male), or WW (non-viable in most species, but
6603-567: The metaphase II stage until fertilization by a sperm. The fertilization event causes intracellular calcium oscillations, and targeted degradation of cyclin B, a regulatory subunit of MPF, thus permitting the MII-arrested oocyte to proceed through meiosis. To initiate parthenogenesis of swine oocytes, various methods exist to induce an artificial activation that mimics sperm entry, such as calcium ionophore treatment, microinjection of calcium ions, or electrical stimulation. Treatment with cycloheximide,
6696-403: The names of Kermes products in other languages. Scale insects vary dramatically in appearance, from very small organisms (1–2 mm) that grow beneath wax covers (some shaped like oysters, others like mussel shells), to shiny pearl-like objects (about 5 mm), to animals covered with mealy wax. Adult females are almost always immobile (apart from mealybugs ) and permanently attached to
6789-403: The need for individuals in a very sparse initial population to search for mates; and an exclusively female sex distribution allows a population to multiply and invade more rapidly (potentially twice as fast). Examples include several aphid species and the willow sawfly, Nematus oligospilus , which is sexual in its native Holarctic habitat but parthenogenetic where it has been introduced into
6882-475: The nest it founds can be provisioned. This provides a means for the mealybug to be dispersed widely. Species of Hippeococcus have long clinging legs with claws to grip the Dolichoderus ants which tend them; they allow themselves to be carried into the ant colony. Here the mealybugs are safe from predation and environmental hazards, while the ants have a source of nourishment. Another species of ant maintains
6975-427: The nuclei fuse or to only those where gametes are mature at the time of fusion. Those cases of automixis that are classified as sexual reproduction are compared to self-fertilization in their mechanism and consequences. The genetic composition of the offspring depends on what type of automixis takes place. When endomitosis occurs before meiosis or when central fusion occurs (restitutional meiosis of anaphase I or
7068-404: The offspring having all of the mother's genetic material are called full clones and those having only half are called half clones. Full clones are usually formed without meiosis. If meiosis occurs, the offspring get only a fraction of the mother's alleles since crossing over of DNA takes place during meiosis, creating variation. Parthenogenetic offspring in species that use either the XY or
7161-463: The phenomenon is called deuterotoky. Parthenogenesis can occur without meiosis through mitotic oogenesis. This is called apomictic parthenogenesis . Mature egg cells are produced by mitotic divisions, and these cells directly develop into embryos. In flowering plants, cells of the gametophyte can undergo this process. The offspring produced by apomictic parthenogenesis are full clones of their mother, as in aphids. Parthenogenesis involving meiosis
7254-412: The plant on which they are feeding. They secrete a waxy coating for defence, making them resemble reptilian or fish scales , and giving them their common name. The key character that sets apart the Coccomorpha from all other Hemiptera is the single segmented tarsus on the legs with only one claw at the tip. The group is extremely sexually dimorphic ; female scale insects, unusual for Hemiptera, retain
7347-489: The plant's vascular system, but a few species feed on fungal mats and fungi , such as some species in the genus Newsteadia in the family Ortheziidae. Plant sap provides a liquid diet which is rich in sugar and non-essential amino acids. In order to make up for the shortage of essential amino acids, they depend on endosymbiotic proteobacteria. Scale insects secrete a large quantity of sticky viscid fluid known as " honeydew ". This includes sugars, amino acids and minerals, and
7440-468: The point that they can easily be overlooked. In some species the hind wings have hamuli , hooklets, that couple the hind wings to the main wings, as in the Hymenoptera . The vestigial wings are often reduced to pseudo- halteres , club-like appendages, but these are not homologous with the control organs of Diptera, and it is not clear whether they have any substantial control function. Hermaphroditism
7533-444: The process of meiosis and are haploid , with half as many chromosomes as their mother's body cells. Haploid individuals, however, are usually non-viable, and parthenogenetic offspring usually have the diploid chromosome number. Depending on the mechanism involved in restoring the diploid number of chromosomes, parthenogenetic offspring may have anywhere between all and half of the mother's alleles . In some types of parthenogenesis
7626-428: The requirement that the egg merely be stimulated by the presence of sperm in order to develop. However, the sperm cell does not contribute any genetic material to the offspring. Since gynogenetic species are all female, activation of their eggs requires mating with males of a closely related species for the needed stimulus. Some salamanders of the genus Ambystoma are gynogenetic and appear to have been so for over
7719-496: The sac has a small opening that allows newly hatched nymphs to emerge. Some species occur under the bark of the host plant and produce little or no ovisac secretion. The bodies of these are often pink or red. Adult females of Eriococcidae usually lay 50-100 eggs. These hatch into first- instar nymphs that emerge from the female's ovisac. The first-instar nymphs develop into second-instar nymphs. From here on, development diverges for females and males: Adult females move around for
7812-501: The scale colony from environmental conditions and predators. The fungus benefits by metabolising the sap extracted from the tree by the insects. Natural enemies include parasitoid wasps , mostly in the families Encyrtidae and Eulophidae , and predatory beetles such as fungus weevils , ladybirds and sap beetles . Ladybirds feed on aphids and scale insects, laying their eggs near their prey to ensure their larvae have immediate access to food. The ladybird Cryptolaemus montrouzieri
7905-422: The sex of fertilized v. unfertilized eggs; and based on how diploidy is restored in unfertilized eggs. The evolution of these systems are thought to be the result of intra- genomic conflict as well as possibly inter-genomic conflict with endosymbionts under varied selection pressures. The diversity of systems has made scale insects ideal models for research. Scale insects are an ancient group, having originated in
7998-454: The sexual phase and are now completely asexual. Many other cases of obligate parthenogenesis (or gynogenesis) are found among polyploids and hybrids where the chromosomes cannot pair for meiosis. The production of female offspring by parthenogenesis is referred to as thelytoky (e.g., aphids) while the production of males by parthenogenesis is referred to as arrhenotoky (e.g., bees). When unfertilized eggs develop into both males and females,
8091-578: The start of the Triassic period, around 245 million years ago, and that the neococcoids appeared during the Early Jurassic, some 185 million years ago. Scale insects are very well represented in the fossil record, with the oldest known member of the group reported from the Late Jurassic amber from Lebanon. They are abundantly preserved in amber from the Early Cretaceous, 130 mya, onwards; they were already highly diversified by Cretaceous times. All
8184-478: The substances they can yield under proper husbandry. Some, such as the cochineal , kermes , lac , Armenian cochineal , and Polish cochineal , have been used to produce red dyes for coloring foods and dyeing fabrics. Both the colour name " crimson " and the generic name Kermes are from Italian carmesi or cremesi for the dye used for Italian silk textiles, in turn from the Persian qirmizī (قرمز), meaning both
8277-700: The superfamily Coccoidea but taxonomic uncertainties have led workers to prefer the use of the infraorder Coccomorpha as the preferred name for the group. Scale insects are members of the Sternorrhyncha . The phylogeny of the extant groups, inferred from analysis of small subunit (18S) ribosomal RNA , is shown in the first cladogram . Psylloidea (jumping plant lice, etc) [REDACTED] Aleyrodoidea (whiteflies) [REDACTED] Coccomorpha (scale insects) [REDACTED] Phylloxeroidea (phylloxera bugs) [REDACTED] Aphididae (aphids) [REDACTED] The timing of phylogenetic diversification within
8370-589: The typical head, thorax and abdomen of other insect groups, and are so different from females that pairing them as a species is challenging. They are usually slender insects resembling aphids or small flies . They have antennae with nine or ten segments, compound eyes (Margarodidae and Ortheziidae) or simple eyes (most other families), and legs with five segments. Most species have wings, and in some, generations may alternate between being winged and wingless. Adult males do not feed, and die within two or three days of emergence. In species with winged males, generally only
8463-405: The young ones to protected sites to feed. In either case, many such species of crawlers, when they moult, lose the use of their legs if they are female, and stay put for life. Only the males retain legs, and in some species wings, and use them in seeking females. To do this they usually walk, as their ability to fly is limited, but they may get carried to new locations by the wind. Adult females of
8556-488: Was described in the fish Poecilia formosa in 1932. Since then at least 50 species of unisexual vertebrate have been described, including at least 20 fish, 25 lizards, a single snake species, frogs, and salamanders. Use of an electrical or chemical stimulus can produce the beginning of the process of parthenogenesis in the asexual development of viable offspring. During oocyte development, high metaphase promoting factor (MPF) activity causes mammalian oocytes to arrest at
8649-440: Was otherwise healthy. This would make him a parthenogenetic chimera (a child with two cell lineages in his body). While over a dozen similar cases have been reported since then (usually discovered after the patient demonstrated clinical abnormalities), there have been no scientifically confirmed reports of a non-chimeric, clinically healthy human parthenote (i.e. produced from a single, parthenogenetic-activated oocyte). In 2007,
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