Fish do not have eyelids, with the exception of the shark. Eyelids are used to protect the eyes from dust and keep them moist; fish do not have these problems underwater, so there is no need for eyelids.
Although fish do not have eyelids, they can sleep. Some float, while others bury themselves or wedge themselves into tight places. Even though they are sleeping, they are still able to sense danger. Fish sleep for as long as they need, depending on how much energy they have exerted during the day.
Fish also lack eyelashes, as they are unnecessary for survival or comfort.Learn More
Fish can lay as few as one egg or as many as 340 million eggs in a season. The amount of eggs varies depending on the fish size and species.Full Answer >
Fish do not have ear openings, but they do each have an inner ear that allows them to hear. Sound transmits directly to water, and that allows fish to hear if people or animals are near them outside of the water.Full Answer >
Fish can drown in water if there is not enough oxygen in the water. Water can run out of oxygen if fish overpopulation uses up the oxygen. Fish require a consistent intake of oxygen to survive. Their gills absorb oxygen from water molecules as water passes through the gill membranes.Full Answer >
Fish, like nearly all living organisms, need to consume water in order to survive. However, fish do not feel thirsty in the same way that humans do. Instead, their bodies have an efficient process that allows them to maintain hydration.Full Answer >