Here, we describe a laboratory experiment as part of an upper-level vertebrate physiology course for biology majors to investigate the physiological response of vertebrates to osmoregulatory challenges. The experiment involves measuring plasma osmolality and Na[superscript +] -K[superscript +] -ATPase activity in gill tissue of teleost fish…

The advantages of using invertebrates in teaching physiological principles are discussed. The ability to illustrate with greater clarity physiological principles, the range and variety of physiological processes available for examination, and the unlimited possibilities for student research are topics of discussion. (KR)