Patterns of Nitrogen Excretion by Embryonic Softshell Turtles (Trionyx spiniferus) Developing in Cleidoic Eggs

Science  09 Sep 1983:
Vol. 221, Issue 4615, pp. 1049-1050
DOI: 10.1126/science.221.4615.1049


Embryonic softshell turtles develop inside eggs exchanging little, if any, liquid water with the nest environment. Despite the consequent restriction on availability of water to support development, embryos convert most of the ammonia released in catabolism of proteins into soluble urea rather than insoluble urate, and thereby commit a portion of their limited reserve of water to serve as solvent for metabolic wastes. This finding is contrary to expectations from prior studies of cleidoic eggs.