How many animals are hermaphrodites?
18611260#2
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 and plants.
Hermaphrodite
18611260#0
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, earthworms 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.
Hermaphrodite
21219782#4
"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.
Triops cancriformis
33726539#3
The copulatory organ is absent in this species. 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 (Patzner 1998). Of 11 females (405–575 mm total length (TL)) examined by Nani and Gneri (1951), those longer than 500 mm were mature. A 507 mm female contained eggs ranging in size from 24.5 x 6.6 to 28 x 8 mm.
Notomyxine tridentiger
1656730#3
Protandrous hermaphrodites are animals that are born male and at some point in their lifespan change sex to female. Protandrous animals include clownfish. Clownfish have a very structured society. In the "Amphiprion percula" species, there are zero to four individuals excluded from breeding and a breeding pair living in a sea anemone. Dominance is based on size, the female being the largest and the male being the second largest. The rest of the group is made up of progressively smaller non-breeders, which have no functioning gonads. If the female dies, the male gains weight and becomes the female for that group. The largest non-breeding fish then sexually matures and becomes the male of the group.
Sequential hermaphroditism
1787105#38
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.
Animal sexual behaviour
1787105#39
Usually hermaphrodites are "sequential", meaning they can switch sex, usually from female to male (protogyny). This can happen if a dominant male is removed from a group of females. The largest female in the harem can switch sex over a few days and replace the dominant male. This is found amongst coral reef fishes such as groupers, parrotfishes and wrasses. It is less common for a male to switch to a female (protandry). As an example, most wrasses are protogynous hermaphrodites within a haremic mating system. Hermaphroditism allows for complex mating systems. Wrasses exhibit three different mating systems: polygynous, lek-like, and promiscuous mating systems.
Animal sexual behaviour
595995#54
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.
Spotted hyena
10524354#6
This makes it easier for the team to work. Among their discoveries, they find out that the hermaphroditic hrossa typically give birth to only one child in a lifetime, and few die early. The occasional second birth makes up for those that do, and the population thus tends to remain stable. Going on a hunt with the hrossa, they learn that they hunt by transmitting a message of "hunger", which brings animals sacrificially to them. The hrossa have sexual intercourse with the animals, and then beat them with a club. The Quakers also tell many stories to the hrossa, hoping to trigger a response and learn more about the planet's natives. Finally, at Thanksgiving, the team leaves back to Swarthmore, and explain their findings to the town.
Pennterra
1656730#5
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