Fish Penis Shape Linked to Predators
The male Bahamas mosquito fish changes the shape of its penis when it senses predators lurking by.
Besides changing mating strategies, scientists at the North Carolina State University found these fish also change the shape and size of their genitalia in the presence of predators. Previous studies revealed that these fish reject elaborate courting rituals and opt for more frequent and sometimes forceful encounters with females.
Researchers Justa Heinen-Kay and assistant professor of biological sciences R. Brian Langerhans found that fish coexisting with predators have longer, bonier and more elongated gonopodium tips than fish living without threat of predation. The gonopodium is the sperm-transferring organ in these live-bearing fish.
Researchers said that the findings suggest that these male fish under constant threat of becoming prey have evolved bonier and more elongated gonopodium tips as a way to copulate even when females don't cooperate."
"Essentially, males need to transfer as much sperm as possible as quickly as possible, and this shape difference could help facilitate that," Langerhans said in a statement.
The study was conducted in the "blue holes" in the Bahamas. These caves have been filled with water in the past 17,000 years.
"Comparing Gambusia across blue holes reveals that predation is associated with evolutionary changes in male genital shape," Langerhans said. "It's a beautiful and elegant system to study the causes and predictability of evolutionary changes."
The findings are published in the Journal of Evolutionary Biology.