Ontogenic screening of aldosterone in the South American toad Bufo arenarum (Hensel).

The content of aldosterone in the South American toad Bufo arenarum embryos developed in Holtfreter's 10% solutions and in distilled water was measured. The screening was carried out on embryos from the following periods of their development: 15 min after fertilization; gray crescent-32 cells; mid cleavage-late gastrula; neural plate-neural tube; tail bud-heart beat; gill circulation-tail fin circulation and operculum fold-complete operculum. The aldosterone content of embryos incubated both in Holtfreter and in distilled water decreased gradually up to gill circulation-tail fin circulation stages. The steroid content of both groups of embryos rose sharply at the end of their development (operculum fold-complete operculum); the observed increase was significantly higher in distilled water animals.