ELEVATED ORNITHINE DECARBOXYLASE ACTIVITY AND POLYAMINE LEVELS DURINGEARLY DEVELOPMENT IN THE BRINE SHRIMP ARTEMIA-FRANCISCANA

Rehydrated Artemia cysts were assayed for ornithine decarboxylase (ODC ) activity and levels of putrescine, spermidine, and spermine during p re-emergent development, emergence and hatching. Low but detectable OD C activity levels increased significantly within 2 hr, suggesting de n ovo synthesis of ODC protein and representing one of the earliest enzy matic biochemical markers in post dormancy development. ODC activity i ncreased 100-fold during preemergent development (occurring in the abs ence of an increase in tissue polyamine content). This increase in enz yme activity occurs in the relative absence of DNA synthesis but may b e related to an enhanced polyamine synthetic capacity necessary for ot her physiological processes such as early transcriptional and translat ional activity. A second, higher ODC activity peak (correlated with a significant increase in polyamines) prior to hatching may be related t o DNA synthesis and other biochemical processes associated with hatchi ng of stage 1 nauplii and is correlated with increasing ecdysteroid ti tres reported previously. Putrescine and spermidine levels were signif icantly higher than spermine levels (2.5, 2.65, and 0.13 mu moles/g dr y weight) at the onset of rehydration. High endogenous polyamines leve ls in encysted embryos are most likely available for use in metabolic processes associated with early differentiation. Polyamine levels incr eased significantly just prior to emergence and continued increasing t hroughout hatching. Spermidine to spermine ratios (>18) should reflect high rates of overall biosynthetic processes throughout preemergence, emergence, and hatching. (C) 1994 Wiley-Liss, Inc.