White Blood Cell Differentials of Northern Cricket Frogs (acris C. Crepitans) with a Compilation of Published Values from Other Amphibians

Herpetologists are becoming increasingly aware of the importance of hematological parameters for evaluating the welfare of their study animals. In particular, differential counts of white blood cells (from blood smears) are now commonly performed on amphibians, although interpretation of such counts relies on some knowledge of the normal range for the species in question, and for many species this range is not known. In this study we examined blood smears from 79 cricket frogs (Acris c. crepitans) from two ponds in northeastern Georgia to establish reference ranges of white blood cell differentials for this species and to explore possible differences in relative white blood cell numbers between sexes, ponds, and body sizes. For comparison, we also compiled values of many other amphibians from published and unpublished records. We found that lymphocytes made up the majority (68.3%) of white blood cells in cricket frogs, followed by neutrophils (22.4%). There was no difference in relative cell numbers of any type between sexes, nor was there an association with body size. Relative numbers of certain cell types (lymphocytes and neutrophils) varied between ponds. In general the values for cricket frogs resembled those of other amphibians, with high numbers of lymphocytes and neutrophils and low numbers of eosinophils, basophils and monocytes. However, in assembling the records for other species we discovered that all Ambystomatid salamanders examined thus far have markedly elevated values of eosinophils compared to other amphibian species. Moreover, their eosinophil counts may be the highest of all vertebrates, and clearly warrant further study to determine their significance.