Coelomic fluid and blood serum proteins of the metamorphosing bullfrog tadpole

Bullfrog Rana catesbeiana tadpoles were divided into four groups containing Gosner ('60) stages as follows: I, 27–31; II, 32–36; III, 37–41; IV, 42–46. Extractable coelomic fluid volume from late metamorphic tadpoles (Group IV) was found to have a highly significant (p<0.001) negative correlation with stage; tadpole weight also had a negative correlation with stage (p<0.025). No significant correlation was found between coelomic fluid volume and tadpole weight. Group IV blood serum protein levels (x = 1.30 ± SEM 0.10 g/100 ml serum) were shown to be significantly higher than corresponding coelomic fluid serum protein levels (x = 0.80 ± 0.06 g/100 ml). Electrophoresis data demonstrated an increase in the albumin fraction of both blood serum and coelomic fluid during metamorphosis. I‐125 labeled human serum albumin equilibrated with the blood serum at equal concentrations about ten hours after an intracoelomic injection. A coelomic fluid turnover time of 26% per hour was calculated from the tracer data. We hypothesize that a slight sieving occurs at the coelomic fluid inflow site with none at the outflow site.