Isosmotic media prevent edema in amphibian larvae without cardiac function

The absence of cardiac and circulatory function causes severe edema in amphibian embryos. Analyzing the roles of embryonic and larval circulation in respiration may thus be confounded by the increased diffusion distance and decreased surface area/volume ratio caused by edema. Similarly, detailed morphological analyses of embryos/larvae with defective circulatory or renal function is difficult or impossible due to the gross morphological anomalies engendered by edematous swelling. To circumvent these problems, two media have been developed which are isosmotic with the plasma of a common experimental amphibian species (Ambystoma mexicanun). These media are remarkably effective in preventing fluid accumulation in embryos and larvae lacking heart function and, when used in slightly lower concentrations, cause no apparent harm to embryos and larvae with normal circulation for periods up to 3 weeks. These media should prove useful for a variety of studies on the developmental physiology of the circulatory system and possibly also when examining the development of renal function and ionoregulation.