Fish have only two chambers in their heart, and blood passes through the heart only once per body cycle. This is because: heart first
○ Fish do not need oxygen
Blood goes to the gills for oxygenation and then directly to the body, without returning to the
○ Fish have no blood vessels
○ Fish have double circulation like mammals
Show explanation
In fish, deoxygenated blood is pumped to the gills where it is oxygenated and then passes directly to the rest of the body, so it goes through the heart only once per cycle.