Osmoregulation by freshwater fish and mosquitoes.

Freshwater mosquito larvae are a good model for osmoregulation by freshwater invertebrates. The larvae of approximately 95% of mosquito species live in freshwater, where they face osmotic challenges very similar to those faced by freshwater fish. Like freshwater fish, mosquito larvae must solve the twin problems of water gain and ion loss. In response, they drink very little water. They conserve ions taken with the diet by absorbing them with cells that line the midgut and rectum, and they secrete a dilute urine. Freshwater mosquito larvae replace the ions lost with urine by actively absorbing Na+ and Cl? from the water with cells in their anal papillae. Freshwater mosquitoes and fish use totally different structures to meet nearly identical environmental challenges.