Hermaphrodite
A hermaphrodite is an organism that possesses both male and female sex organs during its life.[1] In many species, hermaphroditism is a common part of the life-cycle, particularly in some asexual animals and some plants. Hermaphroditism is sometimes considered sexual reproduction, not asexual reproduction. Generally, hermaphroditism occurs in the invertebrates, although it occurs in a fair number of fish, and to a lesser degree in other vertebrates. On very rare occasions, such a hermaphrodite can even impregnate itself, but this will result in complications, such as the offspring having identical DNA to its parent. See Simultaneous Hermaphrodites below.
Historically the term hermaphrodite has also been used to describe ambiguous genitalia and gonadal mosaicism in individuals of unisexual species, especially human beings. The broader term intersex is often used and is preferred by many such individuals and medical professionals.[2] However, some of these people do not like the connotations and misunderstanding of the word "intersexed" and thus prefer to use hermaphrodite instead (Chase, 1998).
In animals
Sequential hermaphrodites
Sequential hermaphrodites (dichogamy) are organisms born as one sex and then later change into the other sex, and can only function as one sex at one time. A few species in this group can sex change multiple times, but they can only function as one sex at a time. Unlike humans, these animal's DNA does not determine their sex, allowing full functional sex change without modifying the DNA.
- Protandry: When the organism starts as a male, and changes sex to a female later in life.
- 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 sex change into a female, and the largest of the non-reproductive males will mature and become reproductive. It has been shown that fishing pressure actually is causing a change in 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: When the organism starts as a female, and changes sex to a male later in life.
- Example: Wrasses (Family Labridae) are reef fish that are all Protogynous, but have two different life strategies:
- #For some species, they all start out as females, and when they get large enough they will sex change to males.
- #Other species start out as females or males (initial phase), and either may shift to become a supermale (terminal phase male). The females and the initial phase males have similar colorations. The supermale is larger and usually brightly colored, and there is only one in a given area of the reef. This supermale dominates the other wrasses of the species, and pair spawns (one male, one female) repeatedly. The initial phase males will group spawn, with many males and females participating. When the supermale dies, the largest wrasse in the area, male or female, changes into the new supermale.
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.
- 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 synchronous 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, wet 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 synchronous 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 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'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.
Asymmetrical Gonadal Dysgenesis versus True Hermaphroditism
Gonadal dysgenesis generally refers to a condition where gonadal development is abnormal. It occurs in about one percent of mammals, including human beings. Asymmetrical Gonadal Dysgensis refers to a condition where the individual has one differentiated gonad (usually testis) and one streak. True Hermaphroditism is rarer in humans and refers to a condition where the individual has both ovarian tissue and testicular elements.[3] It is extremely rare for both sets of organs to be functional; usually neither set is functional. In humans, these manifestations are often altered (sometimes only cosmetically) to resemble standard male or female anatomy shortly after birth.
Fetal hermaphroditism in humans
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.[4] Neither is technically true. Before this stage, humans are simply undifferentiated and possess a Müllerian duct, a Wolffian duct, and a genital tubercle.
In plants
Hermaphrodite is used in botany to describe a flower that has both staminate (male, pollen-producing) and carpelate (female, seed-producing) parts that are self fertile or self pollenizing. Hermaphrodism in plants is more complex than in animals because plants can have hermaphroditic flowers as described, or unisexual flowers with both male and female types developing on the same individual—a closer analogy to animal hermaphrodism. However, this latter condition constitutes monoecy in plants, and is especially common to the conifers, while occurring in only about 7% of angiosperm species (Molnar, 2004).
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 possessing physical traits of both sexes. Thus Hermaphroditus was, by the modern terminology, a simultaneous hermaphrodite. The mythological figure of Tiresias, who figures in the Oedipus cycle as well as the Odyssey, was a sequential hermaphrodite, having been changed from a man to a woman and back by the gods.
See also
- Gonochorism, an alternative reproduction system in which the sexes are distinct, determined genetically and do not change during an individual's lifetime
- Intersex
- Morphodite
- Supernumerary body part
References
- Randall, John E.,(2005) Reef and Shore Fishes of the South Pacific, Univ. of Hawaii Press, p346 and 387. ISBN 0-8248-2698-1
- SeaWorld/Busch Gardens Animal Information Database, "Fish Reproduction"
- Kyu-Rae Kim M.D., et al. True Hermaphroditism and Mixed Gonadal Dysgenesis in Young Children: A Clinicopathologic Study of 10 Cases, Modern Pathology, 2002;15(10):1013
Further reading
- Anne Fausto-Sterling, "How Many Sexes Are There?" from The New York Times, Op-Ed page, March 12, 1993, reprinted in Sterling Harwood, ed., Business as Ethical and Business as Usual (Belmont, CA: Wadsworth Publishing Co., 1996), pages 168-170.
- M.M. Grumbach, and F.A. Conte. 1998. "Disorders of sex differentiation." in Williams Textbook of Endocrinology, eds. J.D. Wilson, D.W. Foster, H.M. Kronenberg, and P.R. Larsen, (Philadelphia: W B Saunders:1303-1425).
- Molnar, Sebastian. 2004. Plant Reproductive Systems, internet version posted February 17, 2004.
- Kyu-Rae Kim M.D., et al. True Hermaphroditism and Mixed Gonadal Dysgenesis in Young Children: A Clinicopathologic Study of 10 Cases, Modern Pathology, 2002;15(10):1013–1019
- Chase, Cheryl. (1998). "Affronting Reason" in Looking Queer: Body Image and Identity as Lesbian, Bisexual, Gay and Transgender Communities, edited by David Atkins, pages 205-219. (Publishing 1998 Haworth Press).
Citations