Serum clinical biochemical and hematologic reference ranges of laboratory-reared and wild-caught Xenopus laevis

The South African clawed frogs Xenopus laevis and X. tropicalis are fully aquatic amphibians and well-established animal models. Because genetically engineered laboratory Xenopus are now being produced, the establishment of normal reference ranges for serum biochemical and hematologic parameters is essential for phenotyping and as a diagnostic aide. We determined normal reference ranges for hematologic values from 3 populations of X. laevis: wild-caught frogs (n = 43) and frogs from 2 commercial sources (A, n = 166; B, n = 109). For serum biochemistry, we determined normal reference ranges for frogs from source A and wild-caught frogs divided by sex and season. Significant differences across populations were found in WBC and RBC counts, hemoglobin concentration, hematocrit, mean corpuscular hemoglobin concentration, and mean corpuscular volume. Among serum biochemical analytes, significant differences were found for albumin:globulin ratio, anion gap, and concentrations of albumin, globulin, total protein, lipase, alanine transaminase, γ-glutamyl transpeptidase; creatine phosphokinase; indirect, direct, and total bilirubin; cholesterol, low-density lipoprotein lipase, carbon dioxide, glucose, lactacte dehydrogenase, calcium, chloride, and sodium. We hypothesize that these differences can be attributed to differences in water quality, habitat, ambient temperature, diet, sex, recent transport or shipment, and genetic background. However, testing that hypothesis is beyond the scope of the current study. In addition, clinical chemistry and hematologic reference range values Xenopus laevis are quite distinct from those for other species and are most consistent with the only values published for another fully aquatic amphibian, the Eastern hellbender (Cryptobranchus alleganiensis).