How many gill slits do most sharks have?

Most sharks have five gill slits on each side of the head.

These openings let water pass over the gills, where oxygen is extracted and carbon dioxide is released. Unlike bony fish, sharks lack a single protective gill cover; each gill opens separately to the outside. Water may enter through the mouth or, in some species, through a small opening behind the eye called a spiracle.

Five is the standard quiz answer, but it is not universal. Some more primitive shark groups have six or seven gill slits, which is why shark anatomy references often describe sharks as having five to seven slits per side. The sixgill sharks are a notable example. The wording “most sharks” correctly points to the common arrangement rather than these exceptions.

Sharks ventilate their gills in two main ways: some actively pump water while resting, while others rely heavily on forward swimming, known as ram ventilation. Rays generally also have five pairs of gill slits.