Scientists have discovered a new species of freshwater fish with remarkable genital features.
The male members of the llanos mosquitofish (Gambusia quadruncus) have hooked genitalia, which they may use to grab onto a resistant female.
The mechanism seems to be an evolutionary response to the female’s blocked genital pore, which makes the females able to be picky about who they mate with.
“Typically, reproduction is more costly in females, so females favor ways of reducing mating with ‘lower quality’ males, but reproduction is cheap in males and so selection favors ways of mating with as many females as possible,” said lead author Brian Langerhans in a statement.
A big ball of tissue blocks most of the genital pore of the female. Normally this “shield” restricts entry of the male’s genitalia, or gonopodium, unless the female deliberately allows the male to mate with her.
However, to overcome this problem, the male evolved four-hooked genitalia which increases their chances of mating success.
“Having four hooks on the gonopodium may provide a means of overcoming female resistance, latching on to the gonopore [genital pore] and transferring sperm in a manner that facilitates effective sperm transfer.” Langerhans explained.
“Or it may serve to stimulate the female in a manner that causes responses in the female that facilitate effective sperm transfer.”
And there’s another sexually-specific characteristic. The females have a colorful anal spot that signals the location of the female’s genital pore, reproductive status, and species. According to Langerhans, the latter could reduce cross-breeding.
Source: Red Orbit
Photo: Brian Langerhans, NC State University
Langerhans1, RB, Gifford, ME, Domínguez-Domínguez, O, García-Bedoya, D, & DeWitt, TJ (2012). Gambusia quadruncus (Cyprinodontiformes: Poeciliidae): a new species of mosquitofish from east-central México. Journal of Fish Biology DOI: 10.1111/j.1095-8649.2012.03397.x