Guppies use sex to suppress native fish species in Mexican rivers and lakes

London, Jan 23 : A new research has suggested that male guppies, which have invaded Mexican rivers and lakes, are sexually harassing females of another fish species to prevent them from reproducing.

Guppies, originally from Trinidad, invaded Mexican waters in the 1950s, a major reason being aquarium owners dumping these fish species into rivers.

According to a report in New Scientist, researchers think that the guppies may physically harm the native females so they are unable to reproduce with males of their own species - a way of suppressing their population.

One species that suffered from the sexual invasion of the guppies was Skiffia bilineata, a fish native to Mexican waters which is threatened with extinction.

Because of the fact that female skiffia look like female guppies, researchers from the Universidad Nacional Aut³noma de Mexico wanted to find out if this was contributing to the species' decline.

They put male and female guppies in aquariums with female skiffia and found that no matter how many female guppies were around, male guppies would try to copulate with females of both species.

Their advances were unsuccessful, but the research team believes that the attempts at sex might be harming the female skiffia. If this is true, the skiffia may not be able to go on to reproduce with males of their own species.

A prominent reason for this is that the two species have very different ways of reproducing.

While Skiffia sex is consensual, guppy sex is more violent, with the males inserting a hookes genital organ known as gonopodium into the females.

Past research has shown that the gonopodium maims guppy females and because the males may attempt to insert this hooked organ into female skiffia, they harm them in the process.

"We see the males draw their gonopodium forward and try to insert it into the genital pore of the Mexican females," said Alejandra Valero, who led the new study. "In some cases, we think they did insert it, because we saw the skiffia females jerking away," she added.

Valero and her colleagues now want to determine whether such interactions do leave female skiffia wounded and if they affect their future reproductive success.

"For me, the most interesting question is whether Mexican females respond differently to their own males after being harassed by guppies?" said Valero.

According to her, "We now know harassment between very different species exists."

ANI