CALCIUM AND pH REQUIREMENTS IN THE CULTURE OF BULLFROG (Rana catesbeiana) LARVAE

Skeletal deformities previously observed in Rana catesbeiana larvae reared in water containing <4 mg/liter calcium were suspected to be caused by calcium deficiencies. Initial studies utilizing the low calckum water showed that an increase of total calcium in the diet from 0.5 to 0.9% significantly (p< .001) reduced the frequency and severity of deformities. Mortality rates of Rana catesbeiana larvae increased significantly (p< .001) at pH levels above 8.1. Newly hatched larvae maintained for three weeks in water buffered at either pH 7.2 or 8.3 experienced mortality rates of 10.0 and 96.7%, respectively. Larvae maintained at pH 7.2 for three weeks and then at pH 8.3 for four weeks experienced higher mortality rates than did a similar group of larvae maintained at pH 7.2 for seven weeks (23.3% and 3.6% respectively). Bacteriological analysis of surviving larvae maintained at pH 7.2 or 8.3 indicated greater numbers of potentially pathogenic bacteria in the carcass and gut of larvae at pH 8.3.