Instruct: Given a question, retrieve documents that answer the question.
Query: How many animals are hermaphrodites?
A rough estimate of the number of hermaphroditic animal species is 65,000.[6] 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 and plants.[6]
This "Journal" narrates the final school year of the student whose diary is included in the text, and reflects on various themes, many of which are to do with individual morality: how, and why, one makes the choices one does and lives the life one lives. The overarching theme of the text, which connects the narratives of Cooper and his student - who together make up the "Hermaphrodite" of the title, is perhaps that of writing: how to write, why to write, and what to write. This theme could be seen to be a further influence from Cyril Connolly, who considers his own failure to produce a major work of literature in Enemies of Promise.
The lack of light requires creatures to have special adaptations to find food, avoid predators, and find mates. Most animals have very large eyes with retinas constructed mainly of rods, which increases sensitivity. Many animals have also developed large feelers to replace peripheral vision. To be able to reproduce, many of these fish have evolved to be hermaphroditic, eliminating the need to find a mate. Many creatures have also developed a very strong sense of smell to detect the chemicals released by mates.
In animals, the different types of change are male to female (protandry), female to male (protogyny), female to hermaphrodite (protogynous hermaphroditism), and male to hermaphrodite (protandrous hermaphroditism). Those that change gonadal sex can have both female and male germ cells in the gonads or can change from one complete gonadal type to the other during their last life stage.
Protogynous hermaphrodites are animals that are born female and at some point in their lifespan change sex to male. As the animal ages, based on internal or external triggers, it shifts sex to become a male animal. Male fecundity increases greatly with age, unlike female.
Sequential hermaphroditism (called dichogamy in botany) is a type of hermaphroditism that occurs in many fish, gastropods, and plants. Sequential hermaphroditism occurs when the individual changes sex at some point in its life.
A couple chemicals that are altered from mutation and have a great impact on mating, are dopamine and serotonin. Each of these chemicals either has a reaction to how the animal acts, or how the species body is formed to benefit their mating success. An example of a mutation in serotonin was found in a species of Nematodes. The serotonin caused their tails to curl during mating, when the mutation occurred the tails did not curl. Without the curling of the tail the nematode was unlikely to find the hermaphrodites sex organs to procreate, and results in less of that nematodes sperm being spread to other offspring. Another example is when the D1 dopamine receptor has a mutation on it; the arousal of a "Drosophila melanogaster" is increased, which also increases the courtship of the animal.
The fitness requirements for androdioecy to arise and sustain itself are theoretically so improbable that it was long considered that such systems do not exist. Particularly, males and hermaphrodites have to have the same fitness, in other words the same number of offspring, in order to be maintained. However, males only have offspring by fertilizing eggs or ovules of hermaphrodites, while hermaphrodites have offspring both through fertilizing eggs or ovules of other hermaphrodites and their own ovules. This means that all else being equal, males have to fertilize twice as many eggs or ovules as hermaphrodites to make up for the lack of female reproduction.
"Triops cancriformis" has a very fast life cycle, and individuals become mature in about two weeks after hatching. Their populations can be gonochoric, hermaphroditic or androdioecious. The latter is a very rare reproductive mode in animals, in which populations are made of hermaphrodites, with a small proportion of males. Due to this lack of males, early researchers thought Triops were parthenogenetic. The presence of testicular lobes scattered amongst their ovaries confirmed they were in fact hermaphroditic. Fertilized females or hermaphrodites produce diapausing eggs or cysts, able to survive decades in the sediment of the ponds and lakes they inhabit. These eggs are resistant to drought and temperature extremes.
The suggested solution put forth by ISNA was to restructure the system of intersex taxonomy and nomenclature to not include the words 'hermaphrodite', 'hermaphroditism', 'sex reversal', or other similar terms. This "standard division of many intersex types into true hermaphroditism, male pseudohermaphroditism, and female pseudohermaphroditism" was described by ISNA and its advocates as confusing and clinically problematic, and a replacement term, disorders of sex development was proposed by Alice Dreger, Cheryl Chase and others in 2005.
All male animals produce spermatocytes, even hermaphrodites such as "C. elegans", which exist as a male or hermaphrodite. In hermaphrodite "C. elegans", sperm production occurs first and is then stored in the spermatheca. Once the eggs are formed, they are able to self-fertilize and produce up to 350 progeny.
Many studies have focused on the proximate causes of sequential hermaphroditism. The role of aromatase has been widely studied in this area. Aromatase is an enzyme that controls the androgen/estrogen ratio in animals by catalyzing the conversion of testosterone into oestradiol, which is irreversible. It has been discovered that the aromatase pathway mediates sex change in both directions. Many studies also involve understanding the effect of aromatase inhibitors on sex change. One such study was performed by Kobayashi et al. In their study they tested the role of estrogens in male three-spot wrasses ("Halichoeres trimaculatus"). They discovered that fish treated with aromatase inhibitors showed decreased gonodal weight, plasma estrogen level and spermatogonial proliferation in the testis as well as increased androgen levels. Their results suggest that estrogens are important in the regulation of spermatogenesis in this protogynous hermaphrodite.
Hermaphroditism occurs when a given individual in a species possesses both male and female reproductive organs, or can alternate between possessing first one, and then the other. Hermaphroditism is common in invertebrates but rare in vertebrates. It can be contrasted with gonochorism, where each individual in a species is either male or female, and remains that way throughout their lives. Most fish are gonochorists, but hermaphroditism is known to occur in 14 families of teleost fishes.
The Hermaphrodite is an incomplete novel by Julia Ward Howe about an intersex individual raised as a male in the United States in the first half of the nineteenth century, who in adulthood lives sometimes as a female and sometimes as a male. Its date of composition is uncertain, but estimated to be between 1846 and 1847. The term "hermaphrodite" was used until the mid-20th century to identify someone having reproductive organs normally associated with both male and female sexes..
During the 15th and 16th centuries, travellers to Africa provided further descriptions of the species. Leo Africanus repeated some of the old concepts on the hyena, with the addition of describing its legs and feet as similar to those of men. In 1551, Swiss naturalist Conrad Gesner rejected the belief of the hyena's hermaphroditism, and theorised that it originated from confusion over an androgynous fish bearing the same name. He adds three other animals within the category of hyenas, including an Ethiopian quadruped named "Crocotta", which was thought to be a hybrid between a hyena and a lioness. Sir Thomas Browne also argued against the hyena's supposed hermaphroditism, stating that all animals follow their own "Law of Coition", and that a hermaphrodite would transgress this. Sir Walter Raleigh, in an attempt to rationalise how Noah's Ark could have fitted all extant species of animal, wrote that hyenas were hybrids between foxes and wolves which originated after the Great Flood. References to the spotted hyena's vocalisations are referenced in numerous contemporary examples of English literature, including Shakespeare's "As You Like It" and George Chapman's "Eastward Ho". John Milton, in his "Samson Agonistes", compares the species to Delila.
A penis (plural "penises" or "penes" ) is the primary sexual organ that male animals use to inseminate sexually receptive mates (usually females and hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males do not bear a penis in every animal species, and in those species in which the male does bear a so-called penis, the penes in the various species are not necessarily homologous. For example, the penis of a mammal is at most analogous to the penis of a male insect or barnacle.
Sex allocation is the allocation of resources to male versus female reproduction in sexual species. In dioecious species, where individuals are male or female for their entire lifetimes, the allocation decision lies between producing male or female offspring. In sequential hermaphrodites, where individuals function as one sex early in life and then switch to the other, the allocation decisions lie in what sex to be first and when to change sex. Animals may be dioecious or sequential hermaphrodites. Sex allocation theory has also been applied to plants, which can be dioecious, simultaneous hermaphrodites, have unisexual plants and hermaphroditic plants in the same population, or have unisexual flowers and hermaphroditic flowers on the same plant.
The mode of reproduction in this kind of organism is external. The copulatory organs are absent. The gonads of hagfishes are situated in the peritoneal cavity. The ovary is found in the anterior portion of the gonad, and the testis is found in the posterior part. The animal becomes female if the cranial part of the gonad develops or male if the caudal part undergoes differentiation. If none develops, then the animal becomes sterile. If both anterior and posterior parts develop, then the animal becomes a functional hermaphrodite. However, hermaphroditism being characterised as functional needs to be validated by more reproduction studies.
Individual shrimps are either male or hermaphrodite. The hermaphrodites can fertilize their own eggs or can mate with males but are unable to mate with other hermaphrodites. This arrangement is called androdioecy and is very rare among animals. The reproductive cycle varies between paired shrimps and isolated hermaphrodites and it is possible that using both strategies enhances the likelihood that fertile eggs will be available when the ephemeral water body in which they live dries up. Although to biologists, androdioecy seems a strategy unlikely to be successful, research using biogeographical, phylogenetic and paleontological evidence has shown that the practice has persisted in the genus "Eulimnadia" for 24 to 180 million years. The shrimps are omnivores and filter feeders, able to feed on the algae and microorganisms that also make use of the revived pool.
Writing that he belongs to the Intersex Society of America, Cal notes that he has not participated in any of the group's rallies because he is not a "political person". While discussing political activism, Cal uses the word "intersex", though in other parts of the novel, he uses the word "hermaphrodite". In the 1920s, Bernice L. Hausman described "intersexuality" as a "continuum of physiological and anatomical sex differences", contesting the notion of a "true sex" concealed in the tissues of the body. Though "hermaphrodite" is burdened by the implications of the anomaly, "intersexuality" is a neologism that tries to "naturalize various sexes, which themselves are naturally occurring." Because Cal uses "hermaphrodite", he indicates that the sole normal genders are the classifications of male and female. Eugenides was asked by an Oprah's Book Club member why he used the term "hermaphrodite" despite its usage being "either terribly ignorant or unforgivably callous". Eugenides replied that he reserved "hermaphrodite" for a literary character: Hermaphroditus. He further stated: "When speaking about real people, I should—and I do my best to—use the term 'intersex'." Noting that one of the initial sources he consulted was the journal "Hermaphrodites with Attitude" published by the Intersex Society of North America, he said that those writers have "co-opted" the term "hermaphrodite". Their action is reminiscent, Eugenides wrote, of how some members of the gay community have "reclaimed" the term "queer". Eugenides stated that it is no surprise that Cal uses "hermaphrodite" and further elaborated: "It's paradoxical: Cal can say 'hermaphodite' but I can't. Or shouldn't."
In a significant shift from publishing a regular journal titled "Hermaphrodites with Attitude" and demonstrating using the same name, the last stated goal of the organization was to eradicate what the organization deemed as "misleading language". The ISNA claimed that nomenclature based on hermaphroditism was stigmatizing to intersex individuals, as well as potentially panic-inducing to parents of intersex children. The suggested solution put forth by the ISNA was to restructure the system of intersex taxonomy and nomenclature to not include the words 'hermaphrodite', 'hermaphroditism', 'sex reversal', or other similar terms. This "standard division of many intersex types into true hermaphroditism, male pseudohermaphroditism, and female pseudohermaphroditism" is described by the ISNA and its advocates as confusing and clinically problematic.
In European societies, Roman law, post-classical Canon law, and later Common law, referred to a person's sex as male, female or hermaphrodite, with legal rights as male or female depending on the characteristics that appeared most dominant. Under Roman law, a hermaphrodite had to be classed as either male or female. The 12th-century "Decretum Gratiani" states that "Whether an hermaphrodite may witness a testament, depends on which sex prevails". The foundation of common law, the 16th Century "Institutes of the Lawes of England" described how a hermaphrodite could inherit "either as male or female, according to that kind of sexe which doth prevaile." Single cases have been described in Canon law and other legal cases over the centuries.
In roundworms, clam shrimp, tadpole shrimp and cancrid shrimps, androdioecy has evolved from dioecy. In these systems, hermaphrodites can only fertilize their own eggs (self-fertilize) and do not mate with other hermaphrodites. Males are the only means of outcrossing. Hermaphrodites may be beneficial in colonizing new habitats, because a single hermaphrodite can generate many other individuals. In the well-studied roundworm Caenorhabditis elegans, males are very rare and only occur in populations that are in bad condition or stressed.
Sequential hermaphrodites (dichogamy) occur in species in which the individual is born as one sex, but can later change into the opposite sex.[12] 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 many gastropods (such as the common slipper shell), and some flowering plants. Sequential hermaphrodites can only change sex once.[13] Sequential hermaphroditism can best be understood in terms of behavioral ecology and evolutionary life history theory, as described in the size-advantage mode[14] first proposed by Michael T. Ghiselin[15] 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.
Currently, hermaphroditism is not to be confused with intersex, as the former refers only to a specific phenotypical presentation of sex organs and the latter to a more complex combination of phenotypical and genotypical presentation. Using "hermaphrodite" to refer to intersex individuals is considered to be stigmatizing and misleading. "Hermaphrodite" is used for animal and vegetal species in which the possession of both ovaries and testes is either serial or concurrent, and for living organisms without such gonads but present binary form of reproduction, which is part of the typical life history of those species; "intersex" has come to be used when this is not the case.