Bubble Nests. Generally, only male bettas blow a bubble nest. Again, this is not absolute, as occasionally a female will blow a bubble nest. However, those instances are fairly rare.

How fish become male or female is far weirder and more varied than the XX-female, XY-male chromosome system of humans. (Though even the human story can get complicated .) ...

Researchers in Colorado have made a startling discovery. Fish, apparently male, are developing female sexual organs. Scientists believe it's the result of too much estrogen in the water and they ...

After around 20 days, the fish have the full male colours and the process is complete. “The bluehead is certainly remarkable for its speed,” says Todd. “Other species do take much longer.” ...

Male live-bearing fish are evolving faster than female fish, according to a Kansas State University study, and that's important for understanding big-picture evolutionary patterns.

WASHINGTON — Abnormally developed fish, possessing both male and female characteristics, have been discovered in the Potomac River in Washington, D.C., and in tributaries across the region ...