Fish with both male and female sex characteristics are considered hermaphrodites. Hermaphroditism itself is the simultaneous (or sequential) presence of female and male sexual characteristics in a living organism, as well as organs for reproduction.
Many species of fish are characterized by a clear separation of their sexes and, as a result, bisexual reproduction. Curiously, some fish are polygamous while others are monogamous. But perhaps the most curious fish are hermaphrodites. Believe it or not, some of these fish can change sex several times throughout their life. Such an individual can function as both female and male. Usually, fish show consistent hermaphroditism, which can be influenced by both the state of the environment and some changes in their population.
There are also such hermaphrodite fish, which at the beginning of their life are males, and later undergo radical metamorphoses of their reproductive system, turning into fully functional females. Here we are already talking about protoandric hermaphroditism. For example, representatives of the sea bass family possess this form of hermaphroditism. Sea wrasses can serve as a striking example of such transformations: all males transform into females with age.
However, in the wrasse family, the opposite process is also observed: if necessary, females can take the places of disappeared males. This happens if a male is removed from a group of wrasses. In this case, the strongest female will begin to demonstrate the behavior of a male, and after two weeks her reproductive system changes dramatically, starting to produce male germ cells.
The hermaphroditism of fish can be not only natural, but also artificial, occurring under the influence of any chemicals. For example, American scientists from the US Geological Survey, who studied the basins of large rivers in the United States, came to the conclusion that mutant fish, which are bisexual creatures, appeared in certain American rivers. It turned out that both smallmouth and largemouth bass are mutant hermaphrodites. Scientists have identified the main habitats of these fish: the Mississippi River, Yamp, Columbia, Colorado, Pee Dee, Rio Grande, Colorado, Apalachicola.
Biologists from the US State Geological Research Center are confident that this phenomenon is not associated with the natural life of these fish. According to them, there is a suspicion that the hormonal changes in these creatures occurred under the influence of disorienting chemical signals in their bodies. It is worth noting that some scientists, who previously argued that these fish change their sex under the influence of various chemicals, do not exclude the possibility of other factors influencing them, since some of these creatures were generally found in fairly clean waters.