Na+, K+ and volume regulation in the mudskipper, Periophthalmus chrysospilos

Abstract

1. 1. Periophthalmus chrysospilos was able to regulate its water content under various conditions except in deionized (DI) water and when on land. 2. 2. Osmolalities of plasma from naudskippers kept out of water or subjected to DI water and 100% SW showed significant changes (P < 0.05) compared to the control fish which has the liberty to be in or out of water. 3. 3. Flux studies using 22Na showed significant increases (P < 0.05) in both the influx (Ki) and efflux (Ke) rate constants in fish subjected to sea-water of higher salinities. 4. 4. Physiological adaptations in high salinities included increase in the gill's ATPase activity and its oxygen consumption. 5. 5. Regulation of its plasma Na+ and K+ concentration is only short termed. Long term subjection of the fish to high salinities revealed an increase in its plasma Na+ and K+content. 6. 6. Consequently, ninhydrin-positive substances (NPS) were involved in intracellular iso-osmotic regulation under long term osmotic stress. © 1987.