A gonopodium is a modified anal fin in males of certain species of live-bearing fish in the familiesAnablepidae and Poeciliidae. It is movable and used to impregnate females during mating. The male`s anal fin’s 3rd, 4th and 5th rays are formed into a tube like structure in which the sperm of the fish is ejected. In some species, the gonopodium may be as much as 50% of the total body length. Occasionally the fin is too long to be used. Hormone treated females may develop gonopodia. These are useless for breeding. One finds similar organs having the same charachteristic in other types of fish, for example the Andropodium in the Hemirhamphodon or in the Goodeidae. In biology, a species is one of the basic units of biodiversity. ... A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ... In biological classification, family (Latin: familia, plural familiae) is 1) a rank or 2) a taxon in that rank. ... [[{{{diversity_link}}}|Diversity]] {{{diversity}}} Binomial name {{{binomial}}} Trinomial name {{{trinomial}}} Type Species {{{type_species}}} Genera Anableps Jenynsia Oxyzygonectes [[Image:{{{range_map}}}|{{{range_map_width}}}|]] Synonyms {{{synonyms}}} Four-eyed fishes, or Anablepidae, are a small group of freshwater and brackish water fishes living on river estuaries in Central and South America. ... Genera Alfaro Belonesox Brachyrhapis Cnesterodon Gambusia (mosquitofishes) Girardichthys Girardinus Heterandria Heterophallus Jenynsia Limia Micropoecilia Phallichthys Phalloceros Phalloptychus Platypoecilus Poecilia (mollies) Poeciliopsis Priapella Pseudoxiphophorus Quitana Xiphophorus (swordtails, platys) Poeciliidae is a family of fresh-water fishes which are live-bearing aquarium fish (they give birth to live young). ...
How it Works
When ready for mating, the gonopodium becomes “erect” and points forward, towards the female. The male shortly inserts the organ into the sex opening of the female. With Hook like adaptations allow the fish to grip onto female to insure impregnation of the female. If a female remains stationary and her partner contacts her vent with his gonopodium, she is fertilized. The sperm is preserved in the female's oviduct. This allows females to, at any time fertilize themselves without the further assistance of males.
These fish out-compete the larger-endowed males in a predator-laden environment because they have a faster burst speed than the males with larger genitalia, who lose out because the size of their organ slows them down, making them ripe for capture by larger fish.
"A male with a larger gonopodium has a higher chance of mating, but in a predator environment he has a higher probability of dying," Langerhans said.
One video was of a male mosquitofish with an average gonopodium; the other was of a male with a 15 percent larger one.
In Anablepinae eyes prominently raised above top of head; each eye divided lengthwise into upper and lower parts giving rise to two pupils each for the right and left eyes; individuals swim with center of eye aligned with the water level and are capable of double vision.
Gonopodium and female genital aperture either dextral or sinistral.
Males with the anterior rays of anal fin crowded, shorter, and partly separate from rest of fin (suspected as a primitive gonopodium called pseudophallus).
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