The Control of Emergence and Metabolism by External Osmotic Pressure and the Role of Free Glycerol in Developing Cysts of Artemia Salina.

An interesting relationship exists between the presence of free glycerol in high concentration and alterations in metabolic rate associated with the onset, duration and termination of dormancy in certain insects. This was first observed by Chino (1957, 1958) in diapausing eggs of the silkworm Bombyx mori, and by Wyatt & Kalf (1958) in diapausing pupae of the giant silkworm Hyalophora cecropia. Since then, considerable attention has been given to analysing the role of glycerol accumulation with respect to diapause (Wyatt & Meyer, 1959; Gilbert & Schneiderman, 1961; Wilhelm, Schneiderman & Daniel, 1961; Wyatt, 1961, 1962; Harvey, 1962; Chino, 1963), and to cold-hardness (Salt, 1958, 1959, 1961; Dubach, Pratt, Smith & Stewart, 1959) in insects. Glycerol has also been found in high concentration in dormant cysts of the brine shrimp Artemia salina (Clegg, 1962), but its physiological significance is not known. Since these cysts consist of an embryo covered by a tough shell (cf. Dutrieu, i960; Nakanishi, Iwasaki, Okigaki & Kato, 1962) the developing embryo must have some mechanism for rupturing this shell when it emerges from the cyst. It seemed possible that glycerol might be involved in shell-rupture because of its presence in high concentration, its relatively low molecular weight, and its well-known hygroscopic properties (Miner & Dalton, 1953). To test this possibility, a study was made of the relationship between external osmotic pressure, the emergence process, and carbohydrate metabolism in developing cysts of Artemia salina. Some of the results of this study will be presented here.