Hermaphrodite

Overview
A hermaphrodite is an organism having both male and female reproductive organs. In many species, hermaphroditism is a common part of the life-cycle, enabling a form of sexual reproduction in which the two sexes are not separated into distinct male and female types of individual. Hermaphroditism most commonly occurs in invertebrates, although it is also found in some fish, and to a lesser degree in other vertebrates.

Historically, the term hermaphrodite has also been used to describe ambiguous genitalia and gonadal mosaicism in individuals of gonochoristic species, especially human beings. The term comes from the name of the minor Greek god Hermaphroditus, son of Hermes and Aphrodite (see below).

Recently, intersex has been used and preferred by many such individuals, encouraging medical professionals to use the term.

Sequential hermaphrodites
Sequential hermaphrodites (dichogamy) occurs 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 teleost fish, especially marine reef species. While some sequential hermaphrodites can change sex multiple times, most can only change sex once.

Sequential hermaphrodites fall into two broad categories:


 * Protandry: Where the 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 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 naturally prefer to catch the larger fish.  The populations are generally changing sex at a smaller size, due to artificial selection.
 * Protogyny: Where the organism starts 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 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.

Sequential hermaphrodites possess an ambisexual gonad. The gonad has both a male and a female portion. When an individual changes sex, gonad remodeling occurs. Interestingly, changes in behavior often occur before these gonad changes.

Simultaneous hermaphrodites
A simultaneous hermaphrodite (or synchronous hermaphrodite) is an adult organism that has both male and female sexual organs at the same time. Usually, self-fertilization does not occur.


 * Snails are perhaps the most classic of simultaneous hermaphrodite, and the most widespread of terrestrial animals possessing this sexual polymorphism. Using calcium carbonate 'arrows' as sperm carriers which are exchanged between snails by shooting them, sexual material is exchanged between both animals. In this way, snails have been poetically compared with Cupid for their sharing of shooting 'Arrows of Love'. After exchange of spermatazoa, both animals will lay fertilized eggs after a period of gestation, which then proceed to hatch after a development period. Snails typically reproduce in early spring and late autumn.
 * 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 nights.


 * Earthworms are another example of a simultaneous hermaphrodite. Although they possess ovaries and testes, they have a protective mechanism against self fertilization and can only function as a single sex at one time. 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.


 * Banana Slugs are one more simultaneous hermaphrodite example. Mating with a partner is most desirable, as the genetic material of the offspring is varied, but if mating with a partner is not possible, self-fertilization is practised.  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's organ will be bitten off (with the slug's radula).  If a banana slug has lost its male sexual organ, it can still self-fertilize, making its hermaphroditic quality an invaluable adaptation.

Other
Hyenas have a clitoris that is greatly enlarged, so much so, that they were described as hermaphrodites -- not only by the ancient Greeks, but as recently as the twentieth century among circus animal handlers -- until scientific information was provided that clarified the misunderstanding.

Botany
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 hermaphrodism in animals is the presence of separate male and female flowers on the same individual&mdash;such plants are called monoecious. Monoecy is especially common in conifers, but occurs in only about 7% of angiosperm species (Molnar, 2004).

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Other uses of the term
Hermaphrodite was used to describe any person incompatible with the biological gender binary, but has recently been replaced by intersexual in medicine. Humans with typical reproductive organs but atypical clitoris/penis are called pseudohermaphrodites in medical literature.

Whether hermaphroditism is a disorder or merely an unusual condition is a matter of opinion. In most societies, the common assumption is that all people are, or at least should be, either male or female. This assumption can make life difficult for hermaphrodites.

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 intersexed, such as some of those with Klinefelter's syndrome and androgen insensitivity syndrome, outwardly appear completely female or male already, without realizing they are intersexed. 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. Intersexuality 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 was so certain of this, in fact, that 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.

Etymology
The term "hermaphrodite" derives from Hermaphroditus, 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 genders. Thus Hermaphroditus could be called, using modern terminology, a simultaneous hermaphrodite. The mythological figure of Tiresias, who figures in the Oedipus cycle as well as the Odyssey, could be called a sequential hermaphrodite, having been changed from a man to a woman and back by the gods.