A
freemartin or
free-martin (sometimes
martin heifer) is an
infertileInfertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...
female
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
which has
masculinizedIn biology and medicine, virilization refers to the biological development of sex differences, changes which make a male body different from a female body. Most of the changes of virilization are produced by androgens...
behavior and non-functioning ovaries. Genetically and externally the animal is female, but it is
sterilizedSterilization is a surgical technique leaving a male or female unable to reproduce. It is a method of birth control. For non-surgical causes of sterility, see infertility.Common sterilization methods include:...
in the wombIn utero is a Latin term literally meaning "in the uterus". It is used in biology to describe the state of an embryo or fetus.-See also:* ex vivo* in silico* in situ* in vitro* in vivo...
by
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
s from a male
twinTwins are two offspring resulting from the same pregnancy, usually born in close succession. They can be the same or different sex. Twins can either be monozygotic or dizygotic ....
, becoming an infertile partial intersex. Freemartinism is the normal outcome of mixed-sex twins in all
cattleThe biological subfamily Bovinae includes a diverse group of 10 genera of medium to large sized ungulates, including domestic cattle, the bison, the water buffalo, the yak, and the four-horned and spiral-horned antelopes...
species that have been studied, and it also occurs occasionally in other mammals including sheep, goats and pigs.
The 18th-century physician
John HunterJohn Hunter FRS was a Scottish surgeon regarded as one of the most distinguished scientists and surgeons of his day. He was an early advocate of careful observation and scientific method in medicine...
discovered that a freemartin always has a male twin.
A
freemartin or
free-martin (sometimes
martin heifer) is an
infertileInfertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...
female
mammalMammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...
which has
masculinizedIn biology and medicine, virilization refers to the biological development of sex differences, changes which make a male body different from a female body. Most of the changes of virilization are produced by androgens...
behavior and non-functioning ovaries. Genetically and externally the animal is female, but it is
sterilizedSterilization is a surgical technique leaving a male or female unable to reproduce. It is a method of birth control. For non-surgical causes of sterility, see infertility.Common sterilization methods include:...
in the wombIn utero is a Latin term literally meaning "in the uterus". It is used in biology to describe the state of an embryo or fetus.-See also:* ex vivo* in silico* in situ* in vitro* in vivo...
by
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
s from a male
twinTwins are two offspring resulting from the same pregnancy, usually born in close succession. They can be the same or different sex. Twins can either be monozygotic or dizygotic ....
, becoming an infertile partial intersex. Freemartinism is the normal outcome of mixed-sex twins in all
cattleThe biological subfamily Bovinae includes a diverse group of 10 genera of medium to large sized ungulates, including domestic cattle, the bison, the water buffalo, the yak, and the four-horned and spiral-horned antelopes...
species that have been studied, and it also occurs occasionally in other mammals including sheep, goats and pigs.
History
The 18th-century physician
John HunterJohn Hunter FRS was a Scottish surgeon regarded as one of the most distinguished scientists and surgeons of his day. He was an early advocate of careful observation and scientific method in medicine...
discovered that a freemartin always has a male twin.
Several researchers made the discovery that a freemartin results when a female fetus has its
chorionThe chorion is one of the membranes that exists during pregnancy between the developing fetus and mother. It is formed by extraembryonic mesoderm and the two layers of trophoblast and surrounds the embryo and other membranes...
fuse in the
uterusThe uterus is a major female hormone-responsive reproductive sex organ of most mammals, including humans. It is within the uterus that the fetus develops during gestation. The term uterus is used consistently within the medical and related professions; the Germanic term, womb is more common in...
with that of a male twin. The result was published in 1916 by Tandler and Keller. The discovery was made independently by American biologist Frank R. Lillie, who published it in
ScienceScience is the academic journal of the American Association for the Advancement of Science and is considered one of the world's most prestigious scientific journals. The peer-reviewed journal, first published in 1880 is circulated weekly and has a print subscriber base of around 130,000...
in 1916. Both teams are now credited with the discovery.
In rural areas
folkloreFolklore is the body of expressive culture, including stories, music, dance, legends, oral history, proverbs, jokes, popular beliefs, customs, and so forth within a particular population comprising the traditions of that culture, subculture, or group. It is also the set of practices through which...
often claimed this condition was not just peculiar to cattle, but extended also to human twins; this belief perpetuated for generations, as was mentioned in the writings of
BedeBede , also Saint Bede, the Venerable Bede, or Beda , was a monk at the Northumbrian monastery of Saint Peter at Monkwearmouth, today part of Sunderland, England, and of its companion monastery, Saint Paul's, in modern Jarrow , both in the Kingdom of Northumbria.He is well known as an author and...
.
Mechanism
In most cattle twins, the blood vessels in the chorions become interconnected, allowing blood from each twin to flow around the other. If both fetuses are the same sex this is of no significance, but if they are different, male
hormoneA hormone is a chemical released by one or more cells that affects cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms...
s pass from the male twin to the female twin. The male hormones then masculinize the female twin, and the result is a freemartin. The degree of masculinization is greater if the fusion occurs earlier in the pregnancy – in about ten percent of cases no fusion takes place and the female remains fertile.
The male twin is largely unaffected by the fusion, although the size of the testicles may be slightly reduced. Testicle size is associated with fertility, so there may be some reduction in bull fertility.
Freemartins behave and grow in a similar way to
castratedCastration is any action, surgical, chemical, or otherwise, by which a male loses the functions of the testicles or a female loses the functions of the ovaries...
male cattle (steers).
Diagnosis
If suspected, a test can be done to detect the presence of the male Y-chromosomes in some circulating white blood cells of the subject. Genetic testing for the Y-chromosome can be performed within days of birth and can aid in the early identification of a sterile female bovine.
Physical examination of the calf may also reveal differences: many (but not all) freemartins have a short
vaginaThe vagina is a fibromuscular tubular tract leading from the uterus to the exterior of the body in female placental mammals and marsupials, or to the cloaca in female birds, monotremes, and some reptiles. Female insects and other invertebrates also have a vagina, which is the terminal part of the...
compared with that of a fertile heifer.
Other animals
A freemartin is the normal outcome of mixed twins in all cattle species which have been studied. It does not normally occur in most other mammals, though it has been recorded in sheep
goatThe domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep: both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s and
pigPigs are a genus of even-toed ungulates within the family Suidae. The name hog most commonly refers to the domestic pig in everyday parlance, but technically encompasses several distinct species, including the wild boar...
s.
Uses
Freemartins are occasionally used in
stem cellStem cells are cells found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiating into a diverse range of specialized cell types. Research in the stem cell field grew out of findings by Canadian...
and
immunologyImmunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all organisms. It deals with, among other things, the physiological functioning of the immune system in states of both health and disease; malfunctions of the immune system in...
research.
During fetal development cells are exchanged between the fused circulations of the bovine twins. Up to 95% of the freemartin's blood cells can be derived from those of its twin brother. Male-derived cells and their progeny can be easily visualized in the freemartin tissues, as only they contain the male
Y chromosomeThe Y chromosome is the sex-determining chromosome in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development, thus determining sex. The human Y chromosome is composed of about 60 million base pairs.- Overview :...
. Thus, by analyzing these tissues, one is able to investigate the capacity of hematopoietic stem cells or other circulating cells to produce other tissues in addition to blood. The freemartin model allows one to analyze perfectly healthy and unmanipulated animals, without resorting to
transplantationOrgan transplant is the moving of an organ from one body to another , for the purpose of replacing the recipient's damaged or failing organ with a working one from the donor site. Organ donors can be living or deceased...
often used in stem cell research.
Fictional use
- In the Aldous Huxley
Aldous Leonard Huxley was an English writer and one of the most prominent members of the famous Huxley family. He spent the later part of his life in the United States, living in Los Angeles from 1937 until his death in 1963...
novel Brave New WorldBrave New World is a novel by Aldous Huxley, written in 1931 and published in 1932. Set in the London of AD 2540 , the novel anticipates developments in reproductive technology and sleep-learning that combine to change society. The future society is an embodiment of the ideals that form the basis...
, a "freemartin" (mentioned in chapters 1, 3, 11 and 17) is a woman who has been deliberately made sterile by exposure to hormones during fetal development; in the book, government policy requires freemartins to form 70% of the female population.
- The Robert A. Heinlein
Robert Anson Heinlein was an American science fiction writer. Often called "the dean of science fiction writers", he was one of the most popular, influential, and controversial authors of the genre. He set a high standard for science and engineering plausibility and helped to raise the genre's...
novel Beyond This HorizonBeyond This Horizon is a science fiction novel by Robert A. Heinlein. It was originally published as a two-part serial in Astounding Science Fiction and then eventually as a single volume by Fantasy Press in 1948.-Overview:The novel depicts a world where genetic selection for increased health,...
lists "the clever and repulsively beautiful pseudo-feminine freemartins" as one of the genetically-engineered specialist types of humans that were created in the "Empire of the Great Khans" (chapter 2).
- In the crime novel Freemartin, by David Cohler, an FtM transgender
Transgender is a general term applied to a variety of individuals, behaviors, and groups involving tendencies to diverge from the normative gender roles....
man is a murderer.
- In the fantasy book series Bazil Broketail
Bazil Broketail is a 1992 fantasy novel by author Christopher Rowley, the name of its main character, and the name of the further series of books featuring him...
by Christopher RowleyChristopher Rowley is an American writer of both science fiction and fantasy novels.Rowley was born in 1948 in Lynn, Massachusetts to an American mother and an English father. Educated for the most part at Brentwood School, Essex, England, he became a London-based journalist in the 1970s...
, "freemartin" is the name for a breed of sterile female dragons.
- In the Robert Heinlein novel Farnham's Freehold
Farnham's Freehold is a science fiction novel set in the near future by Robert A. Heinlein. A serialised version, edited by Frederik Pohl, appeared in Worlds of If magazine . The complete version was published in novel form by G.P...
, the protagonist, Hugh Farnham, is given a companion (bedwarmer) that is described as a natural freemartin.
External links