Na+ and C1– Effluxes and Ionic Regulation in Tilapia Grahami, a Fish Living in Conditions of Extreme Alkalinity

Abstract

The osmoregularity ability of the cichlid Tilapia grahami enables this fish to live in conditions of extreme alkalinity (Reite, Maloiy & Aashaug, 1974; Maloiy et al. 1978). In this paper we describe the ionic balance of T. grahami from Lake Magadi (East African Rift Valley) which has a pH value of around 10, temperature in the range 30–40 °C and an osmotic pressure of about 500 mOsm, the principal inorganic ions being sodium carbonate and bicarbonate (Table 1). We also describe ionic balance of fish in water with a high NaCl concentration and in fresh water.