ABSTRACT
Alcolapia grahami inhabits an extremely stressful aquatic environment of Lake Magadi, Kenya. Significant salt gain and water losses in fish living in a hyperosmotic environment occur through the gill surface and gastro-intestinal tract since the skin and scales offer relatively impermeable surfaces. Since A. grahami lives in a hyperosmotic environment and drinks highly alkaline water at a relatively high rate, the design of the esophagus, stomach and intestines ensures bypassing of an empty stomach by the alkaline water. The aquatic environment of Lake Magadi provides unique respiratory challenges to the inhabitants. Red muscle mitochondria—for which information is available—only exhibit modest evolutionary adjustments in the maximal rate of mitochondrial respiration. Fish living in marine environments, due to the high concentration of salts in the surrounding water, tend to lose water and gain salts while those in freshwater environments lose salts and gain water.
