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Another form of sexual parasitism is hybridogenesis, where the reproductive effort of another species is exploited. One such example is a species in the genus Poeciliopsis. This fish consist only of females that mates with males from a closely related species. All the paternal chromosomes are discarded during the production of eggs.
Spinycheek crayfish (Orconectes limosus) can reproduce both sexually and by parthenogenesis. [20] The Louisiana red swamp crayfish (Procambarus clarkii), which normally reproduces sexually, has also been suggested to reproduce by parthenogenesis, [21] although no individuals of this species have been reared this way in the lab.
[9] [10] [11] This type of reproduction has been induced artificially in a number of animal species that naturally reproduce through sex, including fish, amphibians, and mice. [ 12 ] [ 13 ] Some species reproduce exclusively by parthenogenesis (such as the bdelloid rotifers ), while others can switch between sexual reproduction and parthenogenesis.
One fish species does not reproduce by sexual reproduction but uses sex to produce offspring; Poecilia formosa is a unisex species that uses a form of parthenogenesis called gynogenesis, where unfertilized eggs develop into embryos that produce female offspring.
[citation needed] Internal fertilization with many vertebrates (such as all reptiles, some fish, and most birds) occurs via cloacal copulation, known as cloacal kiss (see also hemipenis), while most mammals copulate vaginally, and many basal vertebrates reproduce sexually with external fertilization.
Marine animals, and particularly bony fish, commonly reproduce by broadcast spawning. This is an external method of reproduction where the female releases many unfertilised eggs into the water. At the same time, a male or many males release a large amount of sperm into the water which fertilises some of these eggs.
Other animals reproduce sexually with external fertilization, including many basal vertebrates. Vertebrates reproduce with internal fertilization through cloacal copulation (in reptiles, some fish, and most birds) [3] or ejaculation of semen through the penis into the female's vagina (in mammals). [4] [5] [3]
Therefore, the Amazon molly can only live in habitats that are also occupied by a species of male that will reproduce with them. [24] The Amazon molly reaches sexual maturity one to six months after birth, and typically has a brood between 60 and 100 fry (young) being delivered every 30–40 days.