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.Know More
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 about Fish
Fish that do not have scales include catfish, sharks, rays, chimaeras, skates, moray eels, sturgeons, paddlefishes, salifin blennies, combtooth blennies, hagfishes and lampreys. Many of these fish have evolved scale alternatives.Full Answer >
Fish can survive in frozen water because only the surface of the water freezes; the fish are able to live life as normal at lower depths beneath the ice. Oxygen is trapped beneath this ice layer, and fish and other creatures living in the water can live quite comfortably despite the frozen surface layer.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 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 >