Who's the Daddy? Female Fish Have Novel Way of Finding Reliable Mates

fishFemale fish have a novel way of finding Mr Right when it comes to picking fathers for their offspring, scientists have revealed. Like most other species of fish, female ocellated wrasse release their eggs into the water for fertilization by males, making just who ends up as the daddy something of a lottery. But now researchers have revealed that females are able to influence which males will succeed in fertilizing their eggs. Writing in the journal Nature Communications, a team of researchers from the US say that the female ocellated wrasse is able to sort Mr Nice from Mr Nasty thanks to a substance, known as ovarian fluid, that coats the eggs she has released. While the researchers are still teasing apart just how the ovarian fluid affects the reproductive success of the males, the study suggests that the ovarian fluid could be affecting the velocity and motion of the sperm. In a number of experiments, the researchers took eggs from female fish and either removed the ovarian fluid, left it in place, or removed it and then re-introduced the fluid. Sperm from both types of male were then introduced to the eggs simultaneously, with the fertilized eggs later analyses to determine their paternity. Further experiments introduced the sperm from each type of male separately to explore whether the influence of the ovarian fluid differed between them.

The results revealed that rather than attracting more nesting males, or simply offering an advantage to their sperm, the ovarian fluid appears to remove the numbers advantage for sperm of the sneaker males.

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