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Penis Fencing
__NOTOC__ Penis fencing is a mating behavior engaged in by many species of flatworm, such as '' Pseudobiceros hancockanus''. Species which engage in the practice are hermaphroditic; each individual has both egg-producing ovaries and sperm-producing testes. The flatworms "fence" using extendable two-headed dagger-like stylets. These stylets are pointed (and in some species hooked) in order to pierce their mate's epidermis and inject sperm into the haemocoel in an act known as intradermal hypodermic insemination, or traumatic insemination. Pairs can either compete, with only one individual transferring sperm to the other, or the pair can transfer sperm bilaterally. Both forms of sperm transfer can occur in the same species, depending on various factors. Unilateral sperm transfer One organism will inseminate the other, with the inseminating individual acting as the "father". The sperm is absorbed through pores or sometimes wounds in the skin from the partner's stylet, causing f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mating Pseudobiceros Bedfordi
In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. ''Fertilization'' is the fusion of two gametes. ''Copulation'' is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization. Mating may also lead to external fertilization, as seen in amphibians, fishes and plants. For most species, mating is between two individuals of opposite sexes. However, for some hermaphroditic species, copulation is not required because the parent organism is capable of self-fertilization (autogamy); for example, banana slugs. The term ''mating'' is also applied to related processes in bacteria, archaea and viruses. Mating in these cases involves the pairing of individuals, accompanied by the pairing of their homologous chromosomes and then exchange of genomic information leading to formation of recombinant progeny (see mating systems). Animals For animals, mating s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bateman's Principle
Bateman's principle, in evolutionary biology, is that in most species, variability in reproductive success (or reproductive variance) is greater in males than in females. It was first proposed by Angus John Bateman (1919–1996), an English geneticist. Bateman suggested that, since males are capable of producing millions of sperm cells with little effort, while females invest much higher levels of energy in order to nurture a relatively small number of eggs, the female plays a significantly larger role in their offspring's reproductive success. Bateman's paradigm thus views females as the limiting factor of parental investment, over which males will compete in order to copulate successfully. Although Bateman's principle served as a cornerstone for the study of sexual selection for many decades, it has recently been subject to criticism. Attempts to reproduce Bateman's experiments in 2012 and 2013 were unable to support his conclusions. Some scientists have criticized Bateman's exp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Love Dart
A love dart (also known as a gypsobelum, shooting darts, or just as darts) is a sharp, calcareous or chitinous dart which some hermaphroditic land snails and slugs create. Love darts are both formed and stored internally in a dart sac. These darts are made in sexually mature animals only, and are used as part of the sequence of events during courtship, before actual mating takes place. Darts are quite large compared to the size of the animal: in the case of the semi-slug genus ''Parmarion'', the length of a dart can be up to one fifth that of the semi-slug's foot. The process of using love darts in snails is a form of sexual selection. Prior to copulation, each of the two snails (or slugs) attempts to "shoot" one (or more) darts into the other snail (or slug). There is no organ to receive the dart; this action is more analogous to stabbing, or to being shot with an arrow or flechette. The dart does not fly through the air to reach its target, but is "fired" as a contact shot. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Traumatic Insemination
Traumatic insemination, also known as hypodermic insemination, is the mating practice in some species of invertebrates in which the male pierces the female's abdomen with his aedeagus and injects his sperm through the wound into her abdominal cavity (hemocoel). The sperm diffuse through the female's hemolymph, reaching the ovaries and resulting in fertilization. The process is detrimental to the female's health. It creates an open wound which impairs the female until it heals, and is susceptible to infection. The injection of sperm and ejaculatory fluids into the hemocoel can also trigger an immune reaction in the female. Bed bugs, which reproduce solely by traumatic insemination, have evolved a pair of sperm-receptacles, known as the spermalege. It has been suggested that the spermalege reduces the direct damage to the female bed bug during traumatic insemination. However experiments found no conclusive evidence for that hypothesis; as of 2003, the preferred explanation for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sexual Conflict
Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction, particularly over the mode and frequency of mating, potentially leading to an evolutionary arms race between males and females. In one example, males may benefit from multiple matings, while multiple matings may harm or endanger females, due to the anatomical differences of that species. Sexual conflict underlies the evolutionary distinction between male and female. The development of an evolutionary arms race can also be seen in the chase-away sexual selection model, which places inter-sexual conflicts in the context of secondary sexual characteristic evolution, sensory exploitation, and female resistance. According to chase-away selection, continuous sexual conflict creates an environment in which mating frequency and male secondary sexual trait development are somewhat in step with the female's degree of resistance. It has primarily been studied ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frot
Frot or frotting (slang for frottage; ) is a non-penetrative form of male-to-male sexual activity that usually involves direct penis-to-penis contact. The term was popularized by gay men activists who disparaged the practice of anal sex, but has since evolved to encompass a variety of preferences for the act, which may or may not imply particular attitudes towards other sexual activities. Owing to its non-penetrative character, frot has the safe sex advantage of minimizing the transmission risk for HIV/AIDS; however, it still carries the risk of skin-to-skin sexually transmitted infections, such as HPV and pubic lice (crabs), both of which can be transmitted even when lesions are not visible. Concept and etymology The modern definition of ''frot'' emerged in a context of a debate about the status of anal sex within the gay male community; some in the anti-anal, pro-frot camp insist that anal sex ought to be avoided altogether. One view argued that the popularity of anal sex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whale
Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and porpoises. Dolphins and porpoises may be considered whales from a formal, cladistic perspective. Whales, dolphins and porpoises belong to the order Cetartiodactyla, which consists of even-toed ungulates. Their closest non-cetacean living relatives are the hippopotamuses, from which they and other cetaceans diverged about 54 million years ago. The two parvorders of whales, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have had their last common ancestor around 34 million years ago. Mysticetes include four extant (living) families: Balaenopteridae (the rorquals), Balaenidae (right whales), Cetotheriidae (the pygmy right whale), and Eschrichtiidae (the grey whale). Odontocetes include the Monodontidae (beluga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bonobo
The bonobo (; ''Pan paniscus''), also historically called the pygmy chimpanzee and less often the dwarf chimpanzee or gracile chimpanzee, is an endangered great ape and one of the two species making up the genus '' Pan,'' the other being the common chimpanzee (''Pan troglodytes''). While bonobos are now recognized as a distinct species in their own right, they were initially thought to be a subspecies of chimpanzee (''Pan troglodytes)'' due to the physical similarities between the two species. Taxonomically, the members of the chimpanzee/bonobo subtribe Panina (composed entirely by the genus '' Pan'') are collectively termed ''panins''. The bonobo is distinguished by relatively long legs, pink lips, dark face, tail-tuft through adulthood, and parted long hair on its head. The bonobo is found in a area of the Congo Basin in the Democratic Republic of the Congo, Central Africa. The species is frugivorous and inhabits primary and secondary forests, including seasonally inundated sw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maritigrella Crozierae
''Maritigrella crozierae'', the tiger flatworm, is a species of marine polyclad flatworm in the family Euryleptidae. It is found on the eastern coasts of North America and the Caribbean Sea where it feeds on colonial sea squirts. Description ''Maritigrella''Maritigrella'': "little tiger of the sea". crozierae'' is a large flatworm. The upper side of its body is boldly striped in yellow and black. The underside is creamy white with a sucker near the centre. The margin is ruffled, rimmed with orange and fringed with small orange tentacles. It has a tubular pharynx and two tentacles at the front of its head, formed from folds of parts of the front of its body. Just behind these is its brain, with two elongated clusters of ocelli (eyespots) on either side. It usually grows to about in length and occasional individuals may reach twice this size. Distribution ''Maritigrella crozierae'' is found in shallow water in the western Atlantic Ocean and the Caribbean Sea. Its range extends ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chelidonura Sandrana
''Chelidonura sandrana'' is a species of sea slug, or "headshield slug", a marine opisthobranch gastropod mollusk in the family Aglajidae.Bouchet, P. (2012). Chelidonura sandrana Rudman, 1973. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=594722 on 2012-06-11 Distribution This species lives from Tanzania to Australia.Rudman W. B. (1998)"''Chelidonura sandrana''" Sea Slug Forum, accessed 25 may 2011. Description Ecology ''Chelidonura sandrana'' is a simultaneously hermaphroditic species. Contrary to classic theoretical predictions, Sprenger et al. (2011) have shown for the first time that the mating rate is largely unresponsive to variations in mate availability in this simultaneous hermaphrodite. With mating rates being close to the female fitness optimum, their findings challenge the prevailing notion of male-driven mating rates in simultaneous hermaphrodites, and call for complementary investigations of ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-insemination
Self-insemination (also known as "selfing") is a mating behavior engaged in by individuals of multiple flatworm species, such as the free-living ''Macrostomum hystrix''.Ramm, S.A., Schlatter, A., Poirier, M., & Schärer, L. (2015). Hypodermic self-insemination as a reproductive assurance strategy. ''Proc. R. Soc.'' ''B'' 282: 20150660. Species that engage in this method of reproduction are hermaphroditic, meaning they possess both male and female reproductive organs. Selfing is referred to as a conditional reproductive strategy in this species, which means that there is a preference to reproduce with a mate.Ramm, S. A., Vizoso, D. B., & Schärer, L. (2012). Occurrence, costs and heritability of delayed selfing in a free-living flatworm. ''Evolutionary Biology'', ''25'', 2559-2568. Sea slugs have also been found to reproduce through self-insemination. Mechanics Self-insemination has been demonstrated in isolated individuals of the flatworm species ''M. hystrix''. This is achiev ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neobenedenia
''Neobenedenia'' is a genus of monopisthocotylean monogenean flatworm parasites. The most common species, ''Neobenedenia melleni'', causes problematic disease in public aquariums. It was named after ichthyologist Ida May Mellen (1877–1970), who worked at the New York Aquarium The New York Aquarium is the oldest continually operating aquarium in the United States, located on the Riegelmann Boardwalk in Coney Island, Brooklyn, New York City. It was founded at Castle Garden in Battery Park, Manhattan in 1896, and moved ... from 1916 to 1929. References Monopisthocotylea Monogenea genera {{Monogenea-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
