Inhibition of emergence, hatching, and protein biosynthesis in embryonic Artemia salina

Abstract

Prior to emergence after about 15 hr of incubation at 25°C, rehydrated cysts appeared quiescent in terms of amino acid and amino sugar exclusion but required to metabolize aerobically for this period. Inhibition of protein biosynthesis with 500 μ M cycloheximide markedly delayed hatching and impaired locomotor activity, although measurable incorporation of exogenous precursors in the period between emergence and hatching was minimal. In cysts incubated with 10 m M KCN, emergence and hatching were delayed. The mechanism chiefly inhibited was identified as the expansion of the hatching membrane sac which separates the embryo from the cyst, but the embryo was not killed. This inhibition in KCN sometimes caused a deranged form of partial emergence in which, typically, the posterior of the embryo and some appendages protruded from the cyst while its anterior remained trapped. Some photomicrographs of this are shown. A model of emergence is proposed in which the expansion of the hatching membrane sac depends upon the continued maintenance of an osmotic gradient by an energy-requiring process.