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| {{about|birth in non-human mammals|birth in humans|Childbirth}} | |||
| {{Other uses}} | {{Other uses}} | ||
| {{multiple issues| | |||
| ] | |||
| {{missing information|birth in non-human mammals | |||
| '''Birth''' is the act or process of bearing or bringing forth ] from the ].<ref>, dictionary.com, Retrieved on June 10, 2010.</ref> In mammals, the process is initiated by hormones which cause the walls of the uterus to contract, expelling the foetus at a developmental stage where it can feed and breathe. In some species the offspring is ] and can move around almost immediately after birth but in others it is ] and completely dependent on its parent. In ]s, the foetus is born at a very immature stage after a short ]al period and develops further in its mother's ]. | |||
| |date=October 2012}} | |||
| {{Prose|date=September 2007}} | |||
| It is not only mammals that give birth. Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. Some of these are ], with the eggs being hatched inside the mother's body, and others are ], with the embryo developing inside her body, as in mammals. Both eventually lead to a live birth. | |||
| {{Cleanup-rewrite|date=May 2009}} | |||
| }} | |||
| ==Human birth== | |||
| ⚫ | {{main|Childbirth}} | ||
| ] ceramic vessel showing a woman giving birth. ] Collection. Lima-Peru]] | ] ceramic vessel showing a woman giving birth. ] Collection. Lima-Peru]] | ||
| The mother's body is prepared for birth by ]s produced by the ], the ] and the ]. The total ] period is about 266 days and the process of giving birth starts with a series of involuntary contractions of the ]. These get stronger and increase in frequency and the head of the baby (unless it is a ]) is pushed against the ]. The cervix gradually dilates, a process that may take many hours, especially in a women bearing her first child. The sac in which the baby is enclosed also helps in the dilatation process but at some stage, the sac bursts and the ] escapes. When the cervix is fully relaxed, further strong contractions of the uterus push the baby out through the ] and the baby is born. Further contractions expel the placenta, usually within a few minutes.<ref name=Dorit>{{cite book |title=Zoology |last1=Dorit |first1=R. L. |last2=Walker |first2=W. F. |last3=Barnes |first3=R. D. |year=1991 |publisher=Saunders College Publishing |isbn=978-0-03-030504-7 |pages=526-527 }}</ref> | |||
| ⚫ | ] calving]] | ||
| ] | |||
| ==Birth in other mammals== | |||
| '''Birth''' ('''calving''' in ] and ], '''whelping''' in ]) is the act or process of bearing or bringing forth ] from the ].<ref>, dictionary.com, Retrieved on June 10, 2010.</ref> The ] is brought forth from the ]. The time of human birth is defined as the time at which the fetus comes out of the mother's womb into the world. Different forms of birth are ], ] and ]. | |||
| Humans are unusual among mammals in producing a single offspring at one time. Other ]s that do this include other ]s, ]s, some ]s, ]s, ]es, ]es, ]s, ]. ]s, ]s and ]s although all may have twins or multiple births on occasions. In these large animals, the birth process is similar to that of a human though in most, the offspring is ]. This means that it is born in a more advanced state than a human baby and is able to stand, walk and run (or swim in the case of an aquatic mammal) shortly after birth.<ref name=Dorit/> In the case of whales, dolphins and porpoises, the single calf is normally born tail first which minimises the risk of drowning.<ref>Mark Simmonds, ''Whales and Dolphins of the World'', New Holland Publishers (2007), Ch. 1, p. 32 ISBN 1845378202.</ref> The mother encourages the newborn calf to rise to the surface to breathe.<ref>{{cite web |url=http://humpbackwhale.homestead.com/Humpback-Whale-Calf.html |title=Humpback Whale Calves |author=Crockett, Gary |year=2011 |publisher=Humpback whales Australia |accessdate=2013-08-28}}</ref> | |||
| ⚫ | ] calving]] | ||
| The birth of a calf to a ] is typical of a larger mammal. The animal seeks a quiet place away from the rest of the herd. The contractions of the uterus are not obvious externally but the cow may be restless and keep getting up and lying down. She may stand with her tail slightly raised and her back arched. The first external sign of the imminent birth is the protrusion of the water bag from the ]. This is followed by first one front foot and rather later by two, which may disappear from view between batches of contractions. By this time the head of the calf is being pushed against the cervix and the ligaments connecting the bones of the pelvis are relaxed. When the cervix has opened sufficiently, further contractions push the calf's head through and the nose, followed by the whole head can be seen projecting externally beside the forelegs. The rest of the birth is usually quite quick and the body of the calf slithers out, wrapped in the amniotic membranes. The cow scrambles to its feet (if lying down at this stage), turns round and starts vigorously licking the calf. The calf takes its first few breaths and within minutes is struggling to rise to its feet. The placenta is usually expelled within a few hours and is often eaten by the normally ] cow. The calf noses under the cow's belly searching for a ] and is soon feeding on the ] produced by the ] in the ].<ref>{{cite web |url=http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex3451 |title=Calving |date=2000-02-01 |publisher=Alberta: Agriculture and Rural Development |accessdate=2013-08-28}}</ref> | |||
| Most smaller mammals have multiple births, producing litters of young which may number twelve or more. In these, each foetus is surrounded by its own placenta and amniotic membranes which separate from the wall of the uterus during labour and work their way towards the vulva. In the ], the arrival of the first puppy is preceded by a bulging dark-coloured sac appearing at the vulva. After further contractions, this bag is expelled with the puppy inside. The bitch breaks the membrane, chews at the umbilical cord and usually eats the afterbirth. She licks the puppy vigorously which stimulates it to breath and it is soon looking for a teat. Meanwhile the next puppy wrapped in its sac is on its way. Each sac contains enough oxygen for the puppy to survive for about six minutes after which time it is likely to die if not yet breathing.<ref>{{cite web |url=http://www.petmd.com/dog/puppycenter/health/evr_dg_whelping_new_puppies_on_the_way |title=Whelping: New Puppies On The Way! |author=Dunn, T.J. |work=Puppy Center |publisher=Pet MD |accessdate=2013-08-28}}</ref> | |||
| ] | |||
| ==Medical meanings== | |||
| An infant ] is born in a very immature state. The gestation period is usually shorter than the intervals between oestrus periods. During gestation there is no placenta but the foetus is contained in a little yellow sac and feeds on a yolk. The first sign that a birth is imminent is the mother cleaning out her ]. When it is born, the infant is pink, blind, furless and a few centimetres long. It has nostrils in order to breathe and forelegs to cling onto its mother's hairs but its hind legs are undeveloped. It crawls through its mother's fur and makes its way into the pouch. Here it fixes onto a teat which swells inside its mouth. It stays attached to the teat for several months until it is sufficiently developed to emerge.<ref>{{cite web |url=http://www.naturalworlds.org/thylacine/biology/reproduction/reproduction_5.htm |title=Reproduction and development |publisher=Thylacine Museum |accessdate=2013-08-28}}</ref> | |||
| * ] is synonymous with placenta, born following the birth of the infant. | |||
| * ] is a birth where the mother delivers the child in a pool of water. | |||
| * ] is the term used for the ] during birth, as it is the route through which the infant passes during a vaginal birth. | |||
| * ] methods are ], medications or behavior patterns employed to reduce the probability of pregnancy. | |||
| * Birth ] is the term for a labor assistant who provides emotional support, physical comfort measures, and other assistance to expectant mothers, partners, families, and ] before, during, and after ]. A postpartum ] provides support after birth, and specializes in postpartum care for mother and infant, infant attachment, and other newborn care. The term "doula" stems from the Greek ''doulos'', or "one who serves." | |||
| * ] or labor pains are the pains felt by the mother during labor, resulting from contractions of the ] and pressure on ]s and ]s. | |||
| * ] or C-section is ] birth through the wall of the ]. | |||
| * ] is the process at the end of a human ] that results in a ] being born. | |||
| * ] is the practice of leaving the ] uncut after birth so that the baby is left attached to its ] until the cord separates naturally. | |||
| * ] is the term for a ] provider who provides at-] for expecting mothers, delivers the ] during birth, and provides ] care. | |||
| * ] is the birth of two (]s), three (triplets), four (quadruplets), etc., babies resulting from a single pregnancy. | |||
| * ] is the technique of minimizing medical intervention, particularly ], during ]. | |||
| * ] is the organ in most female mammals, formed in the lining of the uterus by the union of the uterine mucous membrane with the membranes of the fetus, that provides for the nourishment of the fetus and the elimination of its waste products.<ref></ref> | |||
| * ] (UC) is birth without the aid of medical or professional birth attendants. It is also known as ]. | |||
| ==Birth in other animals== | |||
| ===Complications=== | |||
| The vast majority of invertebrates, most fish, reptiles and amphibians and all birds are ], that is, they lay eggs with little or no embryonic development taking place within the mother. In aquatic organisms, fertilisation is nearly always external with sperm and eggs being liberated into the water. Millions of eggs may be produced with no further parental involvement, in the expectation that a small number may survive to become mature individuals. Terrestrial invertebrates may also produce large numbers of eggs, a few of which may avoid predation and carry on the species. Some fish, reptiles and amphibians have adopted a different strategy and invest their effort in producing a small number of young at a more advanced stage which are more likely to survive to adulthood. Birds care for their young in the nest and provide for their needs after hatching and it is perhaps unsurprising that internal development does not occur in birds, given their need to fly.<ref name=Attenborough>{{cite book |title=The Trials of Life |last=Attenborough |first=David |year=1990 |publisher= |isbn=9780002199124 |pages=26–30 }}</ref> | |||
| * A ] is a physical or mental abnormality present at the time of birth. | |||
| * ] is a theory in pre- and perinatal psychology and natural medicine which hypothesizes that the baby experiences extreme pain during the birthing process, and that this pain influences the child later in life. | |||
| * Complications may cause a ] or spontaneous abortion to occur.<ref>{{cite book |author=Hurwitz, J. and J. Leis |year=1972 |chapter=Directing influence of DNA in the reaction |title=RNA-dependent DNA polymerase activity of RNA tumor viruses |pages=116–129}}</ref> | |||
| * ] treatments are devices, medications, or behavior patterns to increase the probability of pregnancy. | |||
| * ]: ] is a significant musculoskeletal disorder that begins in pregnancy and for some women lasts for years. | |||
| * ] is the birth of an infant before the full term of pregnancy. | |||
| * ] is the birth of a dead fetus or infant. | |||
| * ] is a vaginal birth after a ] birth. | |||
| * | |||
| ] is a mode of reproduction in which ]s develop inside ]s that are retained within the mother's body until they are ready to hatch. Ovoviviparous animals are similar to ] species in that there is ] and the young are born in an advanced state, but differ in that there is no ]l connection and the unborn young are nourished by ]. The mother's body provides ] (respiration), but that is largely necessary for oviparous animals as well.<ref name=Attenborough/> In many ]s the eggs hatch in the oviduct within the mother's body and the embryos are nourished by the egg's yolk and fluids secreted by glands in the walls of the oviduct. The ] sharks practice '']'', where the first embryos to hatch consume the remaining eggs and ] pups ]istically consume neighbouring embryos. The ] maintain a ''placental'' link to the developing young, this practice is known as ]. This is more analogous to mammalian gestation than to that of other fishes. In all these cases, the young are born alive and fully functional.<ref>{{cite web |url=http://www.seaworld.org/animal-info/info-books/sharks-&-rays/birth-&-care.htm |title=Birth and care of young |work=Animals: Sharks and rays |publisher=Busch Entertainment Corporation |accessdate=2013-08-28}}</ref> The majority of ]s are oviviviparous and give birth to already developed offspring. When the young have finished their yolk sacs they feed on nutrients secreted by cells lining the ] and even the cells themselves which they eat with specialist scraping teeth.<ref>{{cite book |title=A Natural History of Amphibians |last1=Stebbins |first1=Robert C. |last2=Cohen |first2=Nathan W. |year=1995 |publisher=Princeton University Press |isbn=978-0-691-03281-8 |pages=172-173 }}</ref> The ] (''Salamandra atra'') and several species of Tanzanian toad in the genus '']'' are oviviviparous, developing through the larval stage inside the mother's oviduct and eventually emerging as fully formed juveniles.<ref>{{cite book |title=A Natural History of Amphibians |last1=Stebbins |first1=Robert C. |last2=Cohen |first2=Nathan W. |year=1995 |publisher=Princeton University Press |isbn=978-0-691-03281-8 |page=204 }}</ref> | |||
| ==Legal meanings== | |||
| * ] is a legal document describing details of a person's birth. | |||
| *] is a day to celebrate that the person has lived a certain number of years. It is an annual event based either on the anniversary of a person's date of birth, or on ] birthtime calculations. | |||
| * A ] comprising the fathers, mothers, brothers or sisters, is an institution where the members are related by birth, marriage, or a similar partnership or spousal relationship. | |||
| * In some countries a person is considered of ] if the child is born of parents not legally married to one another. | |||
| A more developed form of ] called ] is adopted by some species of ]s<ref>Capinera, John L., ''Encyclopedia of entomology''. Springer Reference, 2008, p. 3311.</ref> and cockroaches,<ref>Costa, James T., ''The Other Insect Societies''. Belknap Press, 2006, p. 151.</ref> certain genera of ], ]s and ]s. In these, the developing embryo is nourished by some form of placental structure. Many species of ] are viviparous. Some are ovoviviparous but others such as members of the genera '']'' and '']'', give birth to live young that develop internally, deriving their nourishment from a mammal-like placenta attached to the inside of the mother's uterus. In a recently described example, an African species, ''Trachylepis ivensi'', has developed a purely reptilian ] directly comparable in structure and function to a mammalian placenta.<ref>{{cite journal |author=Blackburn, Daniel G.; Flemming, Alexander F. |year=2012 |title=Invasive implantation and intimate placental associations in a placentotrophic African lizard, ''Trachylepis ivensi'' (Scincidae) |journal=Journal of Morphology |volume=273 |issue=2 |pages=137–159 |doi=10.1002/jmor.11011 }}</ref> | |||
| ==Spiritual meanings== | |||
| ] | |||
| * ] is based upon the belief that an individual's life is influenced by the ] positions of the ], ], and ] in the ] or below the ] at the moment of birth; a ] is calculated using the exact time, date, and ] to try to interpret these cyclical influences on a person's ]. | |||
| * ], a term used primarily in ] ], is associated with ], ], and ] rebirth. | |||
| * ] is a belief that a person is born again after their death based on the ] of their previous births. | |||
| * ] is the Muslim and Christian doctrine that asserts that Jesus Christ was born to a ], and thus that his conception was carried out without a father. | |||
| ] giving birth]] | |||
| ==See also== | |||
| Some insects also give birth to offspring that are miniature versions of the adult. The ] has a complex life cycle and during the summer months is able to multiply with great rapidity. Their reproduction is typically ] and viviparous. Females produce unfertilised eggs <ref>{{Cite journal| doi = 10.1111/j.1095-8312.1979.tb00038.x| issn = 1095-8312| volume = 11| issue = 3| pages = 259–277| last = Blackman| first = Roger L| title = Stability and variation in aphid clonal lineages| journal = Biological Journal of the Linnean Society | date = 1979 }}</ref> which they retain within their bodies. The embryos develop within their mothers' ] and the offspring are ]s of their mothers. Female ] are born which grow rapidly and soon produce more female offspring themselves. In some instances, the newborn nymphs already have developing embryos inside them.<ref name=Attenborough/> | |||
| ⚫ | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| * ] | |||
| ==References== | ==References== | ||
| {{reflist}} | {{reflist}} | ||
| == External links == | |||
| {{wiktionary}} | |||
| ] | |||
| ] | ] | ||
| ] | ] | ||
Revision as of 10:34, 29 August 2013
For other uses, see Birth (disambiguation).
Birth is the act or process of bearing or bringing forth offspring from the uterus. In mammals, the process is initiated by hormones which cause the walls of the uterus to contract, expelling the foetus at a developmental stage where it can feed and breathe. In some species the offspring is precocial and can move around almost immediately after birth but in others it is altricial and completely dependent on its parent. In marsupials, the foetus is born at a very immature stage after a short gestational period and develops further in its mother's pouch.
It is not only mammals that give birth. Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. Some of these are ovoviviparous, with the eggs being hatched inside the mother's body, and others are vivparous, with the embryo developing inside her body, as in mammals. Both eventually lead to a live birth.
Human birth
Main article: Childbirth
The mother's body is prepared for birth by hormones produced by the pituitary gland, the ovary and the placenta. The total gestation period is about 266 days and the process of giving birth starts with a series of involuntary contractions of the uterus. These get stronger and increase in frequency and the head of the baby (unless it is a breech birth) is pushed against the cervix. The cervix gradually dilates, a process that may take many hours, especially in a women bearing her first child. The sac in which the baby is enclosed also helps in the dilatation process but at some stage, the sac bursts and the amniotic fluid escapes. When the cervix is fully relaxed, further strong contractions of the uterus push the baby out through the vagina and the baby is born. Further contractions expel the placenta, usually within a few minutes.
Birth in other mammals
Humans are unusual among mammals in producing a single offspring at one time. Other mammals that do this include other primates, horses, some antelopes, giraffes, hippopotamuses, rhinoceroses, elephants, seals. whales, dolphins and porpoises although all may have twins or multiple births on occasions. In these large animals, the birth process is similar to that of a human though in most, the offspring is precocial. This means that it is born in a more advanced state than a human baby and is able to stand, walk and run (or swim in the case of an aquatic mammal) shortly after birth. In the case of whales, dolphins and porpoises, the single calf is normally born tail first which minimises the risk of drowning. The mother encourages the newborn calf to rise to the surface to breathe.
The birth of a calf to a cow is typical of a larger mammal. The animal seeks a quiet place away from the rest of the herd. The contractions of the uterus are not obvious externally but the cow may be restless and keep getting up and lying down. She may stand with her tail slightly raised and her back arched. The first external sign of the imminent birth is the protrusion of the water bag from the vulva. This is followed by first one front foot and rather later by two, which may disappear from view between batches of contractions. By this time the head of the calf is being pushed against the cervix and the ligaments connecting the bones of the pelvis are relaxed. When the cervix has opened sufficiently, further contractions push the calf's head through and the nose, followed by the whole head can be seen projecting externally beside the forelegs. The rest of the birth is usually quite quick and the body of the calf slithers out, wrapped in the amniotic membranes. The cow scrambles to its feet (if lying down at this stage), turns round and starts vigorously licking the calf. The calf takes its first few breaths and within minutes is struggling to rise to its feet. The placenta is usually expelled within a few hours and is often eaten by the normally herbivorous cow. The calf noses under the cow's belly searching for a teat and is soon feeding on the colostrum produced by the mammary glands in the udder.
Most smaller mammals have multiple births, producing litters of young which may number twelve or more. In these, each foetus is surrounded by its own placenta and amniotic membranes which separate from the wall of the uterus during labour and work their way towards the vulva. In the dog, the arrival of the first puppy is preceded by a bulging dark-coloured sac appearing at the vulva. After further contractions, this bag is expelled with the puppy inside. The bitch breaks the membrane, chews at the umbilical cord and usually eats the afterbirth. She licks the puppy vigorously which stimulates it to breath and it is soon looking for a teat. Meanwhile the next puppy wrapped in its sac is on its way. Each sac contains enough oxygen for the puppy to survive for about six minutes after which time it is likely to die if not yet breathing.
An infant marsupial is born in a very immature state. The gestation period is usually shorter than the intervals between oestrus periods. During gestation there is no placenta but the foetus is contained in a little yellow sac and feeds on a yolk. The first sign that a birth is imminent is the mother cleaning out her pouch. When it is born, the infant is pink, blind, furless and a few centimetres long. It has nostrils in order to breathe and forelegs to cling onto its mother's hairs but its hind legs are undeveloped. It crawls through its mother's fur and makes its way into the pouch. Here it fixes onto a teat which swells inside its mouth. It stays attached to the teat for several months until it is sufficiently developed to emerge.
Birth in other animals
The vast majority of invertebrates, most fish, reptiles and amphibians and all birds are oviparous, that is, they lay eggs with little or no embryonic development taking place within the mother. In aquatic organisms, fertilisation is nearly always external with sperm and eggs being liberated into the water. Millions of eggs may be produced with no further parental involvement, in the expectation that a small number may survive to become mature individuals. Terrestrial invertebrates may also produce large numbers of eggs, a few of which may avoid predation and carry on the species. Some fish, reptiles and amphibians have adopted a different strategy and invest their effort in producing a small number of young at a more advanced stage which are more likely to survive to adulthood. Birds care for their young in the nest and provide for their needs after hatching and it is perhaps unsurprising that internal development does not occur in birds, given their need to fly.
Ovoviviparity is a mode of reproduction in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch. Ovoviviparous animals are similar to viviparous species in that there is internal fertilization and the young are born in an advanced state, but differ in that there is no placental connection and the unborn young are nourished by egg yolk. The mother's body provides gas exchange (respiration), but that is largely necessary for oviparous animals as well. In many sharks the eggs hatch in the oviduct within the mother's body and the embryos are nourished by the egg's yolk and fluids secreted by glands in the walls of the oviduct. The Lamniforme sharks practice oophagy, where the first embryos to hatch consume the remaining eggs and sand tiger shark pups cannibalistically consume neighbouring embryos. The requiem sharks maintain a placental link to the developing young, this practice is known as viviparity. This is more analogous to mammalian gestation than to that of other fishes. In all these cases, the young are born alive and fully functional. The majority of caecilians are oviviviparous and give birth to already developed offspring. When the young have finished their yolk sacs they feed on nutrients secreted by cells lining the oviduct and even the cells themselves which they eat with specialist scraping teeth. The Alpine salamander (Salamandra atra) and several species of Tanzanian toad in the genus Nectophrynoides are oviviviparous, developing through the larval stage inside the mother's oviduct and eventually emerging as fully formed juveniles.
A more developed form of vivipary called placental viviparity is adopted by some species of scorpions and cockroaches, certain genera of sharks, snakes and velvet worms. In these, the developing embryo is nourished by some form of placental structure. Many species of skink are viviparous. Some are ovoviviparous but others such as members of the genera Tiliqua and Corucia, give birth to live young that develop internally, deriving their nourishment from a mammal-like placenta attached to the inside of the mother's uterus. In a recently described example, an African species, Trachylepis ivensi, has developed a purely reptilian placenta directly comparable in structure and function to a mammalian placenta.
Some insects also give birth to offspring that are miniature versions of the adult. The aphid has a complex life cycle and during the summer months is able to multiply with great rapidity. Their reproduction is typically parthenogenetic and viviparous. Females produce unfertilised eggs which they retain within their bodies. The embryos develop within their mothers' ovarioles and the offspring are clones of their mothers. Female nymphs are born which grow rapidly and soon produce more female offspring themselves. In some instances, the newborn nymphs already have developing embryos inside them.
References
- Birth, dictionary.com, Retrieved on June 10, 2010.
- ^ Dorit, R. L.; Walker, W. F.; Barnes, R. D. (1991). Zoology. Saunders College Publishing. pp. 526–527. ISBN 978-0-03-030504-7.
- Mark Simmonds, Whales and Dolphins of the World, New Holland Publishers (2007), Ch. 1, p. 32 ISBN 1845378202.
- Crockett, Gary (2011). "Humpback Whale Calves". Humpback whales Australia. Retrieved 2013-08-28.
- "Calving". Alberta: Agriculture and Rural Development. 2000-02-01. Retrieved 2013-08-28.
- Dunn, T.J. "Whelping: New Puppies On The Way!". Puppy Center. Pet MD. Retrieved 2013-08-28.
- "Reproduction and development". Thylacine Museum. Retrieved 2013-08-28.
- ^ Attenborough, David (1990). The Trials of Life. pp. 26–30. ISBN 9780002199124.
- "Birth and care of young". Animals: Sharks and rays. Busch Entertainment Corporation. Retrieved 2013-08-28.
- Stebbins, Robert C.; Cohen, Nathan W. (1995). A Natural History of Amphibians. Princeton University Press. pp. 172–173. ISBN 978-0-691-03281-8.
- Stebbins, Robert C.; Cohen, Nathan W. (1995). A Natural History of Amphibians. Princeton University Press. p. 204. ISBN 978-0-691-03281-8.
- Capinera, John L., Encyclopedia of entomology. Springer Reference, 2008, p. 3311.
- Costa, James T., The Other Insect Societies. Belknap Press, 2006, p. 151.
- Blackburn, Daniel G.; Flemming, Alexander F. (2012). "Invasive implantation and intimate placental associations in a placentotrophic African lizard, Trachylepis ivensi (Scincidae)". Journal of Morphology. 273 (2): 137–159. doi:10.1002/jmor.11011.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - Blackman, Roger L (1979). "Stability and variation in aphid clonal lineages". Biological Journal of the Linnean Society. 11 (3): 259–277. doi:10.1111/j.1095-8312.1979.tb00038.x. ISSN 1095-8312.