In biology, a hermaphrodite is an organism that has complete or
partial reproductive organs and produces gametes 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 either partner can act as the "female" or
"male". For example, the great majority of tunicates, 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 intersex has
come into preferred usage for humans, since the word hermaphrodite is
considered to be misleading and stigmatizing, as well as
"scientifically specious and clinically problematic".
A rough estimate of the number of hermaphroditic animal species is
65,000. Since the estimated total number of animal species is 8.6
million, the percentage of animal species that are hermaphroditic is
about 0.7%. Arthropods are the phylum with the largest number of
species. Most hermaphroditic species exhibit some degree of
self-fertilization. The distribution of self-fertilization rates among
animals is similar to that of plants, suggesting that similar
processes are operating to direct the evolution of selfing in animals
2.1 Sequential hermaphrodites
2.2 Simultaneous hermaphrodites
5 See also
7 Further reading
8 External links
The term derives from the Latin: hermaphroditus, from Ancient Greek:
ἑρμαφρόδιτος, translit. hermaphroditos, which
Hermaphroditus (Ἑρμαφρόδιτος), the son of
Aphrodite in Greek mythology. According to Ovid, he fused
with the nymph
Salmacis resulting in one individual possessing
physical traits of male and female sexes; according to the earlier
Diodorus Siculus, he was born with a physical body combining male and
female sexes. The word hermaphrodite entered the
English lexicon as
early as the late fourteenth century. Alexander ab Alexandro
stated, using the term hermaphrodite, that the people who bore the
sexes of both man and woman were regarded by the Athenians and the
Romans as monsters, and thrown into the sea at Athens and into the
Tiber at Rome.
Main article: Sequential hermaphroditism
Crepidula fornicata (common slipper shell).
Clownfish are initially male; the largest fish in a group becomes a
Most species of parrotfish start life as females and later change into
Sequential hermaphrodites (dichogamy) occur in species in which the
individual is born as one sex, but can later change into the opposite
sex. This contrasts simultaneous hermaphrodites, in which an
individual may possess fully functional male and female genitalia.
Sequential hermaphroditism is common in fish (particularly teleost
fish) and some jellyfish, many gastropods (such as the common slipper
shell), and some flowering plants. Sequential hermaphrodites can only
change sex once.
Sequential hermaphroditism can best be understood
in terms of behavioral ecology and evolutionary life history theory,
as described in the size-advantage mode 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 can be divided into three broad categories:
Protandry: Where an organism is born as a male, and then changes sex
to a female.
Example: The clownfish (genus Amphiprion) are colorful reef fish found
living in symbiosis with sea anemones. 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-reproductive 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 selection.
Protogyny: Where the organism is born as a female, and then changes
sex to a male.
Example: wrasses (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 and 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
Sex Changers: where an organism has female and male
reproductive organs, but act as either female or male during different
stages in life.
Lythrypnus dalli (Family Lythrypnus) are a group of coral
reef fish in which bidirectional sex change occurs. Once a social
hierarchy is established a fish changes sex according to its social
status, regardless of the initial sex, based on a simple principle: if
the fish expresses subordinate behavior then it changes its sex to
female, and if the fish expresses dominant or not subordinate behavior
then the fish changes its sex to male.
Dichogamy can have both conservation-related implications for humans,
as mentioned above, as well as economic implications. For instance,
groupers 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.
Turbellarians mating by penis fencing. Each has two penises on the
undersides of their heads which they use to inject sperm.
Earthworms are simultaneous hermaphrodites, having both male and
female reproductive organs.
A simultaneous (or synchronous) hermaphrodite (or homogamous) is an
adult organism that has both male and female sexual organs at the same
Self-fertilization often occurs.
Reproductive system of gastropods:
Pulmonate land snails and land
slugs 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 spermatophore, which can then be stored in the spermatheca. After
exchange of spermatozoa, both animals will lay fertilized eggs after a
period of gestation; then the eggs will proceed to hatch after a
Snails typically reproduce in early spring and
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 radula), see apophallation. If a banana slug has
lost its male sexual organ, it can still mate as a female, making its
hermaphroditic quality a valuable adaptation.
Hamlets, 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
Earthworms 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 gametes, 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.
The free-living hermaphroditic nematode Caenorhabditis elegans
reproduces primarily by self-fertilization, but infrequent
out-crossing events occur at a rate of approximately 1%.
The mangrove killifish (Kryptolebias marmoratus) is a species of fish
that lives along the east coast of North, Central and South America.
These fish are simultaneous hermaphrodites. K. marmoratus produces
eggs and sperm by meiosis and routinely reproduces by
self-fertilization. Each individual hermaphrodite normally fertilizes
itself when an egg and sperm produced by an internal organ unite
inside the fish’s body.
Main article: Pseudohermaphroditism
When spotted hyenas were first discovered by explorers, they were
thought to be hermaphrodites. Early observations of spotted hyenas in
the wild led researchers to believe that all spotted hyenas, male and
female, were born with what appeared to be a penis. The apparent penis
in female spotted hyenas is in fact an enlarged clitoris, which
contains an external birth canal. It can be difficult to
determine the sex of wild spotted hyenas until sexual maturity, when
they may become pregnant. When a female spotted hyena gives birth,
they pass the cub through the cervix internally, but then pass it out
through the elongated clitoris.
Main article: Intersex
Hermaphroditus, the "son" of the Greek god
Hermes and the goddess
Aphrodite, origin of the word "hermaphrodite".
1860 photograph by Nadar of an intersex person displaying genitalia,
one of a nine-part series. The series may be the earliest medical
photographic documentation of intersex.
Hermaphrodite is used in older literature to describe any person whose
physical characteristics do not neatly fit male or female
classifications, but the term has been replaced by intersex. Intersex
describes a wide variety of combinations of what are considered male
and female biology.
Intersex biology may include, for example,
ambiguous-looking external genitalia, karyotypes that include mixed XX
Y chromosome pairs (46XX/46XY, 46XX/47XXY or 45X/XY mosaic).
Clinically, medicine currently describes intersex people as having
disorders of sex development, a term vigorously contested.
This is particularly because of a relationship between medical
terminology and medical intervention.
Intersex civil society
organizations, and many human rights institutions, have
criticized medical interventions designed to make intersex bodies more
typically male or female.
Some people who are intersex, such as some of those with androgen
insensitivity syndrome, outwardly appear completely female or male,
frequently 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.
Some humans were historically termed true hermaphrodites if their
gonadal tissue contained both testicular and ovarian tissue, or
pseudohermaphrodites if their external appearance (phenotype) differed
from sex expected from internal gonads. This language has fallen out
of favor due to misconceptions and pejorative connotations associated
with the terms, and also a shift to nomenclature based on
Intersex is in some caused by unusual sex hormones; the unusual
hormones may be caused by an atypical set of sex chromosomes. One
possible pathophysiologic explanation of intersex in humans is a
parthenogenetic 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
(ovotestes) and genetic sex. Another common cause of being intersex is
the crossing over of the
SRY from the
Y chromosome to the X chromosome
during meiosis. The
SRY is then activated in only certain areas,
causing development of testes in some areas by beginning a series of
events starting with the upregulation of SOX9, and in other areas not
being active (causing the growth of ovarian tissues). Thus, testicular
and ovarian tissues will both be present in the same individual.
Fetuses before sexual differentiation are sometimes described as
female by doctors explaining the process. This is technically not
true. Before this stage, humans are simply undifferentiated and
possess a Müllerian duct, a Wolffian duct, and a genital tubercle.
Hylocereus undatus, a hermaphrodite plant with both carpels and
Sexual reproduction in plants
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 botany 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.
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Look up hermaphrodite in Wiktionary, the free dictionary.
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Britannica Online Encyclopedia: hermaphroditism (biology)
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The Evolution of Self-Fertile Hermaphroditism: The Fog Is Clearing
Hermaphrodite – Pictorial Profile", about Lynn Edward
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