What is the function of the nictitating membrane in a frog?

The nictitating membrane in a frog is a transparent or translucent third eyelid that helps protect the eye and keep it moist. It is located on the inner corner of the eye and can be drawn across the eye to provide an additional layer of protection. The nictitating membrane also helps to clean and lubricate the surface of the eye, especially when the frog is swimming or hunting underwater.

In addition to these protective functions, the nictitating membrane can also help frogs see underwater by increasing their ability to focus and reducing glare. It can also help to shield the eye from bright light or debris in the environment.

Overall, the nictitating membrane in frogs serves as an important adaptation for their survival in different environments and helps to maintain the health and function of their eyes.