Question

If you experimentally reversed the flow of water over the gills of a fish, so that the water was flowing in the same direction as the blood through the gill capillaries, what would happen?

Gas exchange efficiency would decrease

Gas exchange efficiency would increase

Gases would move in the opposite directions (CO₂ would enter the body and O₂would leave)

There would be no effect since the length of time the water and blood flow past each other remains the same.

Answer 1

Option a) gas exchange efficiency would decrease

In counter current system, fluids flow in opposite directions in the tubes. In gills flow of water and blood occur in opposite directions, this will help in extraction of maximum amount of oxygen by blood from the water. As partial pressure difference will always exist between water and blood. If both water and blood flow in same direction, then there will be maximum 50 percent oxygen will be trapped from water while it is 100 percent in counter current system. So there will be decreased gas exchange in the system.