Blink and You'll Miss It
Male mosquitofish can complete mating in under one second — among the fastest sex acts in the animal kingdom.
The mosquitofish holds a remarkable record: one-second sex. Males have evolved to mate so quickly that the entire act takes less time than a single heartbeat.
Male mosquitofish have a modified anal fin called a gonopodium — essentially a tube for delivering sperm. During mating, the male approaches the female and swings this organ forward in a lightning-fast thrust. The entire process takes about 0.5 to 1 second.
This speed evolved because female mosquitofish don't want to mate. They actively avoid and resist male attempts. The males' only option is to be so fast that females can't escape.
Scientists call these rapid, non-consensual matings "sneak copulations" or "forced matings." Males who can complete the act faster are more successful at reproducing, driving the evolution of ever-faster mating.
This creates an evolutionary arms race: females evolve to be better at avoiding males, while males evolve to be faster. The result is the blink-and-you-miss-it mating we see today.
Mosquitofish are livebearers, meaning females give birth to live young rather than laying eggs. A single mating can fertilize multiple batches of offspring.