• pH value controls movement: In sea urchin and salmon sperm, the pH value regulates whether they remain immotile or swim.

• An enzyme as a pH sensor: A rising pH activates soluble adenylyl cyclase (sAC) in sea urchins and fish. This produces the messenger substance cAMP, which is essential for sperm movement.

• Universal mechanism: The regulation of cAMP concentration via the pH sensor sAC could be widespread among marine invertebrates and fish.

• Impact on reproduction: As lakes and oceans become more acidic due to climate change and increased carbon dioxide levels, this could negatively impact reproduction of many marine organisms.