Nucleotide Metabolism during Brine Shrimp Embryogenesis

Changes in the amounts of acid-soluble nucleotides during embryonic development of the encysted egg of the brine shrimp, Artemia salina, have been determined. Significant quantities of diguanosine tetraphosphate, the most abundant compound in the nucleotide pool, are apparently not utilized until hatching, at which time the amount falls precipitously. Diguanosine triphosphate, a homologue of the tetraphosphate, does not change appreciably in amount throughout development, but may participate in a reaction catalyzed by a nucleoside phosphokinase. Adenosine triphosphate increases over 5-fold during the first few hours of development and again after hatching, but is virtually absent from the dormant cyst. Early development is associated with the rapid appearance of nucleotides in the hatch medium. These nucleotides appear to arise by diffusion from cracked and nonviable eggs and not by an active secretory process of the normally developing embryo.