Evidence is presented for the existence of a circulating erythropoiesis stimulating factor in the bled fish (blue gourami).
Erythropoiesis is inhibited by starvation and increased following a single bleeding in the gourami.
Administration of serum from the bled gourami to the starved gourami evokes a highly significant increase in erythropoiesis. Serum from normal non-bled fish fails to produce this effect.
Large doses of sheep plasma ESF and human urinary ESF (16 units/100 Gm. body weight) stimulate erythropoiesis in the starved gourami. Smaller amounts, highly active in the polycythemic mouse, are without effect in the gourami.
No in vitro stimulatory effect on radioiron uptake by peripheral red blood cells of the gourami was exerted by anemic gourami serum or mammalian ESF.
The starved gourami may find use as a test animal for erythropoietic factors from other lower vertebrates.