The metabolic status of diapause embryos of Artemia franciscana (SFB)

The brine shrimp Artemia franciscana is widely used in aquaculture and basic research in areas ranging from molecular biology to evolution and ecology. A key feature of its life history involves the production of encysted embryos whose development is halted (enters diapause) at the gastrula stage. These shelled embryos are released into the aqueous environment where diapause continues until terminated by suitable conditions that produce an ''activated embryo,'' which then can resume development when conditions permit. Very little is known about the metabolism of diapause embryos, in contrast to activated embryos, which have been studied extensively. We have examined selected features of metabolism in diapause embryos produced in laboratory cultures and collected from the field. Although in a state of developmental arrest, newly released diapause embryos are shown to carry on a vigorous metabolism. However, as diapause continues metabolism slows until its detection becomes an experimental problem; it is possible that metabolism comes to a reversible standstill. We also present results from studies on diapause termination and the resumption of metabolism. Finally, we will show that a major protein (p26), previously implicated as a potential molecular chaperone in activated embryos undergoing anoxia and thermal shock, behaves similarly in diapause embryos Although direct evidence is lacking, that result suggests a role for p26 that may be common to the mechanisms involved with the control of diapause as well as the stress response in this system.