Hermaphrodite
Encyclopedia
In biology
, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.
Many taxonomic groups of animals (mostly invertebrates) do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction
in which both partners can act as the "female" or "male". For example, the great majority of pulmonate snails, opisthobranch snails and slugs are hermaphrodites. Hermaphroditism is also found in some fish species and to a lesser degree in other vertebrates. Most plants are also hermaphrodites.
Historically, the term hermaphrodite has also been used to describe ambiguous genitalia and gonadal mosaicism in individuals of gonochoristic species, especially human beings. The word hermaphrodite entered the English lexicon in the 15th century, derived from the Greek Hermaphroditos a combination of the names of the gods Hermes
(male) and Aphrodite
(female). Recently, the word "intersex
" has come into preferred usage for humans, since the word "hermaphrodite" is considered to be misleading and stigmatizing, and "scientifically specious and clinically problematic."
Sequential hermaphrodites (dichogamy
) occur in species
in which the individual is born as one sex, but can later change into the alternate sex. This is in contrast with simultaneous hermaphrodites, in which an individual may possess fully functional male and female gonads. Sequential hermaphroditism is common in fish (particularly teleost fish), many gastropods (such as the common slipper shell
), and some flowering plants. While some sequential hermaphrodites can change sex multiple times, most can only change sex once. Sequential hermaphrodism can best be understood in terms of behavioral ecology
and evolutionary life history theory
, as described in the size-advantage model first proposed by Michael T. Ghiselin which states that if an individual of a certain sex could significantly increase its reproductive success after reaching a certain size, it would be to their advantage to switch to that sex.
Sequential hermaphrodites fall into two broad categories:
Dichogamy can have both conservation-related implications for humans, as mentioned above, as well as economic implications. For instance, grouper
s are favoured fish for eating in many Asian countries and are often aquacultured. Since the adults take several years to change from female to male, the broodstock
are extremely valuable individuals.
A simultaneous (or synchronous) hermaphrodite (homogamy
) is an adult organism that has both male and female sexual organs at the same time. Usually, self-fertilization does not occur.
in humans differs from pseudohermaphroditism
in which the person has both X and Y chromosomes (not to be confused with the normal XY chromosome of males), having both testicular and ovarian tissue, and having both but ambiguous-looking external genitalia.
One possible pathophysiologic explanation of this rare phenomenon is a parthenogentic
division of a haploid ovum into two haploid ova. Upon fertilization of the two ova by two sperm cells (one carrying an X
and the other carrying a Y
chromosome), the two fertilized ova
are then fused together
resulting in a person having dual genitalial, gonadal and genetic sex
.
Hermaphrodite is used in botany
to describe a flower
that has both staminate
(male, pollen-producing) and carpellate (female, ovule-producing) parts. This condition is seen in many common garden plants. A closer analogy to hermaphroditism in animals is the presence of separate male and female flowers on the same individual—such plants are called monoecious. Monoecy is especially common in conifers
, but occurs in only about 7% of angiosperm species.
, but has recently been replaced by intersex
in medicine. Humans with typical reproductive organs but atypical clitoris/penis are called pseudohermaphrodites in medical literature. Pseudohermaphroditism also refers to a human possessing both the clitoris and testicles.
People with intersex conditions sometimes choose to live exclusively as one sex or the other, using clothing, social cues, genital surgery, and hormone replacement therapy to blend into the sex they identify with more closely. Some people who are intersex, such as some of those with androgen insensitivity syndrome
, outwardly appear completely female or male already, without realizing they are intersex. Other kinds of intersex conditions are identified immediately at birth because those with the condition have a sexual organ larger than a clitoris and smaller than a penis. Intersex is thought by some to be caused by unusual sex hormones; the unusual hormones may be caused by an atypical set of sex chromosomes.
Sigmund Freud
(based on work by his associate Wilhelm Fliess
) held fetal hermaphroditism to be a fact of the physiological development of humans. He based much of his theory of innate sexuality on that assumption. Similarly, in contemporary times, fetuses before sexual differentiation
are sometimes described as female by doctors explaining the process. Neither concept is technically true. Before this stage, humans are simply undifferentiated and possess a Müllerian duct
, a Wolffian duct
, and a genital tubercle
.
, the son of Hermes
and Aphrodite
in Greek mythology
, who was fused with a nymph
, Salmacis
, resulting in one individual possessing physical traits of both sexes.
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.
Many taxonomic groups of animals (mostly invertebrates) do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction
Sexual reproduction
Sexual reproduction is the creation of a new organism by combining the genetic material of two organisms. There are two main processes during sexual reproduction; they are: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the...
in which both partners can act as the "female" or "male". For example, the great majority of pulmonate snails, opisthobranch snails and slugs are hermaphrodites. Hermaphroditism is also found in some fish species and to a lesser degree in other vertebrates. Most plants are also hermaphrodites.
Historically, the term hermaphrodite has also been used to describe ambiguous genitalia and gonadal mosaicism in individuals of gonochoristic species, especially human beings. The word hermaphrodite entered the English lexicon in the 15th century, derived from the Greek Hermaphroditos a combination of the names of the gods Hermes
Hermes
Hermes is the great messenger of the gods in Greek mythology and a guide to the Underworld. Hermes was born on Mount Kyllini in Arcadia. An Olympian god, he is also the patron of boundaries and of the travelers who cross them, of shepherds and cowherds, of the cunning of thieves, of orators and...
(male) and Aphrodite
Aphrodite
Aphrodite is the Greek goddess of love, beauty, pleasure, and procreation.Her Roman equivalent is the goddess .Historically, her cult in Greece was imported from, or influenced by, the cult of Astarte in Phoenicia....
(female). Recently, the word "intersex
Intersex
Intersex, in humans and other animals, is the presence of intermediate or atypical combinations of physical features that usually distinguish female from male...
" has come into preferred usage for humans, since the word "hermaphrodite" is considered to be misleading and stigmatizing, and "scientifically specious and clinically problematic."
Sequential hermaphrodites
Dichogamy
Sequential hermaphroditism is a type of hermaphroditism that occurs in many fish, gastropods and plants. Here, the individual is born one sex and changes sex at some point in their life. They can change from a male to female , or from female to male...
) occur in species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
in which the individual is born as one sex, but can later change into the alternate sex. This is in contrast with simultaneous hermaphrodites, in which an individual may possess fully functional male and female gonads. Sequential hermaphroditism is common in fish (particularly teleost fish), many gastropods (such as the common slipper shell
Common slipper shell
The common slipper shell, Crepidula fornicata, has many other common names including common Atlantic slippersnail, boat shell, quarterdeck shell, fornicating slipper snail, and it is known in Britain as the "common slipper limpet"...
), and some flowering plants. While some sequential hermaphrodites can change sex multiple times, most can only change sex once. Sequential hermaphrodism can best be understood in terms of behavioral ecology
Behavioral ecology
Behavioral ecology, or ethoecology, is the study of the ecological and evolutionary basis for animal behavior, and the roles of behavior in enabling an animal to adapt to its environment...
and evolutionary life history theory
Life history theory
Life history theory posits that the schedule and duration of key events in an organism's lifetime are shaped by natural selection to produce the largest possible number of surviving offspring...
, as described in the size-advantage model first proposed by Michael T. Ghiselin which states that if an individual of a certain sex could significantly increase its reproductive success after reaching a certain size, it would be to their advantage to switch to that sex.
Sequential hermaphrodites fall into two broad categories:
- Protandry: Where an organism is born as a male, and then changes sex to a female.
- Example: The clownfishClownfishClownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Twenty-eight species are recognized, one in the genus Premnas, while the remaining are in the genus Amphiprion. In the wild they all form symbiotic mutualisms with sea anemones...
(genus Amphiprion) are colorful reef fish found living in symbiosisSymbiosisSymbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
with sea anemoneSea anemoneSea anemones are a group of water-dwelling, predatory animals of the order Actiniaria; they are named after the anemone, a terrestrial flower. Sea anemones are classified in the phylum Cnidaria, class Anthozoa, subclass Zoantharia. Anthozoa often have large polyps that allow for digestion of larger...
s. Generally one anemone contains a 'harem ', consisting of a large female, a smaller reproductive male, and even smaller non-reproductive males. If the female is removed, the reproductive male will change sex and the largest of the non-re productive males will mature and become reproductive. It has been shown that fishing pressure can change when the switch from male to female occurs, since fishermen usually prefer to catch the larger fish. The populations are generally changing sex at a smaller size, due to natural selectionNatural selectionNatural selection is the nonrandom process by which biologic traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution....
.
- Example: The clownfish
- Protogyny: Where the organism is born as a female, and then changes sex to a male.
- Example: wrasseWrasseThe wrasses are a family, Labridae, of marine fish, many of which are brightly colored. The family is large and diverse, with over 600 species in 82 genera, which are divided into nine subgroups or tribes....
s (Family Labridae) are a group of reef fish in which protogyny is common. Wrasses also have an uncommon life history strategy, which is termed diandry (literally, two males). In these species, two male morphs exists: an initial phase male or a terminal phase male. Initial phase males do not look like males and spawn in groups with other females. They are not territorial. They are, perhaps, female mimics (which is why they are found swimming in group with other females). Terminal phase males are territorial and have a distinctively bright coloration. Individuals are born as males or females, but if they are born males, they are not born as terminal phase males. Females and initial phase males can become terminal phase males. Usually, the most dominant female or initial phase male replaces any terminal phase male when those males die or abandon the group.
- Example: wrasse
Dichogamy can have both conservation-related implications for humans, as mentioned above, as well as economic implications. For instance, grouper
Grouper
Groupers are fish of any of a number of genera in the subfamily Epinephelinae of the family Serranidae, in the order Perciformes.Not all serranids are called groupers; the family also includes the sea basses. The common name grouper is usually given to fish in one of two large genera: Epinephelus...
s are favoured fish for eating in many Asian countries and are often aquacultured. Since the adults take several years to change from female to male, the broodstock
Broodstock
Broodstock, or broodfish, are a group of mature individuals used in aquaculture for breeding purposes. Broodstock can be a population of animals maintained in captivity as a source of replacement for, or enhancement of, seed and fry numbers. These are generally kept in ponds or tanks in which...
are extremely valuable individuals.
Simultaneous hermaphrodites
Homogamy
-In sociology:Homogamy is marriage between individuals who are, in some culturally important way, similar to each other. Homogamy may be based on socio-economic status, class, gender, ethnicity, or religion...
) is an adult organism that has both male and female sexual organs at the same time. Usually, self-fertilization does not occur.
- Reproductive system of gastropodsReproductive system of gastropodsThe reproductive system of gastropods varies greatly from one group to another within this very large and diverse taxonomic class of animals...
: Pulmonate land snailLand snailA land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
s and land slugSlugSlug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
s are perhaps the best-known kind of simultaneous hermaphrodite, and are the most widespread of terrestrial animals possessing this sexual polymorphism. Sexual material is exchanged between both animals via spermatophoreSpermatophoreA spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...
, which can then be stored in the spermathecaSpermathecaThe spermatheca , also called receptaculum seminis , is an organ of the female reproductive tract in insects, some molluscs, oligochaeta worms and certain other invertebrates and vertebrates...
. After exchange of spermatozoaSpermatozoonA spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
, both animals will lay fertilized eggs after a period of gestation; then the eggs will proceed to hatch after a development period. Snails typically reproduce in early spring and late autumn. - :Banana slugs are one example of a hermaphroditic gastropod. Mating with a partner is more desirable biologically, as the genetic material of the resultant offspring is varied, but if mating with a partner is not possible, self-fertilization is practiced. The male sexual organ of an adult banana slug is quite large in proportion to its size, as well as compared to the female organ. It is possible for banana slugs, while mating, to become stuck together. If a substantial amount of wiggling fails to separate them, the male organ will be bitten off (using the slug's radulaRadulaThe radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
), see apophallationApophallationApophallation is a technique resorted to by some species of air-breathing land slugs such as Limax maximus and Ariolimax spp. In these species of hermaphroditic terrestrial gastropod mollusks, after mating, if the slugs cannot successfully separate, a deliberate amputating of the penis takes...
. If a banana slug has lost its male sexual organ, it can still mate as a female, making its hermaphroditic quality a valuable adaptation. - HamletsHamlet (fish)A hamlet is a fish of the genus Hypoplectrus that is found mainly in coral reefs in the Caribbean Sea and the Gulf of Mexico, particularly around Florida and the Bahamas...
, unlike other fish, seem quite at ease mating in front of divers, allowing observations in the wild to occur readily. They do not practice self-fertilization, but when they find a mate, the pair takes turns between which one acts as the male and which acts as the female through multiple matings, usually over the course of several nights. - EarthwormEarthwormEarthworm is the common name for the largest members of Oligochaeta in the phylum Annelida. In classical systems they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, even though the internal male segments are anterior to the female...
s are another example of a simultaneous hermaphrodite. Although they possess ovaries and testes, they have a protective mechanism against self fertilization. Sexual reproduction occurs when two worms meet and exchange gameteGameteA gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...
s, copulating on damp nights during warm seasons. Fertilized eggs are protected by a cocoon, which is buried on or near the surface of the ground.
Pseudohermaphroditism
When hyenas were first discovered by explorers, they were thought to be hermaphrodites. Observation of packs of hyenas in the wild (in the 1960s) revealed all hyenas, male and female, are born with what appears to be a penis. The two genders are almost impossible to tell apart until they reach sexual maturity and they either have babies or don't. The apparent penis in females is an external birth canal. When the babies are born, they pass through the cervix internally, but then pass into this external canal, which is less muscular than a usual birth canal.Humans
True hermaphroditismTrue hermaphroditism
True hermaphroditism is a medical term for an intersex condition in which an individual is born with ovarian and testicular tissue.There may be an ovary on one side and a testis on the other, but more commonly one or both gonads is an ovotestis containing both types of tissue.It is rare—so...
in humans differs from pseudohermaphroditism
Pseudohermaphroditism
Pseudohermaphroditism, or pseudo-hermaphroditism, is the condition in which an organism is born with secondary sex characteristics or a phenotype that is different from what would be expected on the basis of the gonadal tissue ....
in which the person has both X and Y chromosomes (not to be confused with the normal XY chromosome of males), having both testicular and ovarian tissue, and having both but ambiguous-looking external genitalia.
One possible pathophysiologic explanation of this rare phenomenon is a parthenogentic
Parthenogenesis
Parthenogenesis is a form of asexual reproduction found in females, where growth and development of embryos occur without fertilization by a male...
division of a haploid ovum into two haploid ova. Upon fertilization of the two ova by two sperm cells (one carrying an X
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
and the other carrying a Y
Y chromosome
The Y chromosome is one of the two sex-determining chromosomes in most mammals, including humans. In mammals, it contains the gene SRY, which triggers testis development if present. The human Y chromosome is composed of about 60 million base pairs...
chromosome), the two fertilized ova
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...
are then fused together
Chimera (genetics)
A chimera or chimaera is a single organism that is composed of two or more different populations of genetically distinct cells that originated from different zygotes involved in sexual reproduction. If the different cells have emerged from the same zygote, the organism is called a mosaic...
resulting in a person having dual genitalial, gonadal and genetic sex
Sex-determination system
A sex-determination system is a biological system that determines the development of sexual characteristics in an organism. Most sexual organisms have two sexes. In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual...
.
Botany
Hermaphrodite is used in botany
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...
to describe a flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
that has both staminate
Stamen
The stamen is the pollen producing reproductive organ of a flower...
(male, pollen-producing) and carpellate (female, ovule-producing) parts. This condition is seen in many common garden plants. A closer analogy to hermaphroditism in animals is the presence of separate male and female flowers on the same individual—such plants are called monoecious. Monoecy is especially common in conifers
Pinophyta
The conifers, division Pinophyta, also known as division Coniferophyta or Coniferae, are one of 13 or 14 division level taxa within the Kingdom Plantae. Pinophytes are gymnosperms. They are cone-bearing seed plants with vascular tissue; all extant conifers are woody plants, the great majority being...
, but occurs in only about 7% of angiosperm species.
Other uses of the term
Hermaphrodite was used to describe any person incompatible with the biological gender binaryGender binary
The gender binary is the classification of sex and gender into two distinct and disconnected forms of masculine and feminine. It is one general type of a gender system. It can describe a social boundary that discourages people from crossing or mixing gender roles, or from creating other third ...
, but has recently been replaced by intersex
Intersex
Intersex, in humans and other animals, is the presence of intermediate or atypical combinations of physical features that usually distinguish female from male...
in medicine. Humans with typical reproductive organs but atypical clitoris/penis are called pseudohermaphrodites in medical literature. Pseudohermaphroditism also refers to a human possessing both the clitoris and testicles.
People with intersex conditions sometimes choose to live exclusively as one sex or the other, using clothing, social cues, genital surgery, and hormone replacement therapy to blend into the sex they identify with more closely. Some people who are intersex, such as some of those with androgen insensitivity syndrome
Androgen insensitivity syndrome
Androgen insensitivity syndrome is a condition that results in the partial or complete inability of the cell to respond to androgens. The unresponsiveness of the cell to the presence of androgenic hormones can impair or prevent the masculinization of male genitalia in the developing fetus, as...
, outwardly appear completely female or male already, without realizing they are intersex. Other kinds of intersex conditions are identified immediately at birth because those with the condition have a sexual organ larger than a clitoris and smaller than a penis. Intersex is thought by some to be caused by unusual sex hormones; the unusual hormones may be caused by an atypical set of sex chromosomes.
Sigmund Freud
Sigmund Freud
Sigmund Freud , born Sigismund Schlomo Freud , was an Austrian neurologist who founded the discipline of psychoanalysis...
(based on work by his associate Wilhelm Fliess
Wilhelm Fliess
Wilhelm Fliess was a German Jewish otolaryngologist who practised in Berlin. On Josef Breuer's suggestion, Fliess attended several "conferences" with Sigmund Freud beginning in 1887 in Vienna, and the two soon formed a strong friendship...
) held fetal hermaphroditism to be a fact of the physiological development of humans. He based much of his theory of innate sexuality on that assumption. Similarly, in contemporary times, fetuses before sexual differentiation
Sexual differentiation
Sexual differentiation is the process of development of the differences between males and females from an undifferentiated zygote...
are sometimes described as female by doctors explaining the process. Neither concept is technically true. Before this stage, humans are simply undifferentiated and possess a Müllerian duct
Müllerian duct
Müllerian ducts are paired ducts of the embryo that run down the lateral sides of the urogenital ridge and terminate at the Müllerian eminence in the primitive urogenital sinus. In the female, they will develop to form the Fallopian tubes, uterus, cervix, and the upper two-third of the vagina; in...
, a Wolffian duct
Wolffian duct
The mesonephric duct is a paired organ found in mammals including humans during embryogenesis....
, and a genital tubercle
Genital tubercle
A phallic tubercle or genital tubercle is a body of tissue present in the development of the urinary and reproductive organs. It forms in the ventral, caudal region of mammalian embryos of both sexes, and eventually develops into a phallus...
.
Etymology
The term "hermaphrodite" derives from HermaphroditusHermaphroditus
In Greek mythology, Hermaphroditus or Hermaphroditos was the child of Aphrodite and Hermes. He was a minor deity of bisexuality and effeminacy. According to Ovid, born a remarkably handsome boy, he was transformed into an androgynous being by union with the water nymph Salmacis...
, the son of Hermes
Hermes
Hermes is the great messenger of the gods in Greek mythology and a guide to the Underworld. Hermes was born on Mount Kyllini in Arcadia. An Olympian god, he is also the patron of boundaries and of the travelers who cross them, of shepherds and cowherds, of the cunning of thieves, of orators and...
and Aphrodite
Aphrodite
Aphrodite is the Greek goddess of love, beauty, pleasure, and procreation.Her Roman equivalent is the goddess .Historically, her cult in Greece was imported from, or influenced by, the cult of Astarte in Phoenicia....
in Greek mythology
Greek mythology
Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...
, who was fused with a nymph
Nymph
A nymph in Greek mythology is a female minor nature deity typically associated with a particular location or landform. Different from gods, nymphs are generally regarded as divine spirits who animate nature, and are usually depicted as beautiful, young nubile maidens who love to dance and sing;...
, Salmacis
Salmacis
In Greek mythology, Salmacis was an atypical naiad who rejected the ways of the virginal Greek goddess Artemis in favour of vanity and idleness. Her attempted rape of Hermaphroditus places her as the only nymph rapist in the Greek mythological canon ."There dwelt a Nymph, not up for hunting or...
, resulting in one individual possessing physical traits of both sexes.
Further reading
- Discovery Health Channel, (2007) "I Am My Own Twin", reprinted in: