Paraffin section is commonly used for skin characterization in amphibians. However, the standard of sampling design for this group of animals still remains largely unexplored. Because characteristics such as capillary density that cannot be measured directly may require large sample sizes, an exploration of the ideal sampling design for quantifying them will be beneficial. In this study, we quantified the density of capillaries beneath the epidermis in the Emei mustache toad (Leptobrachium boringii) and examined the required sample size through resampling simulations. We obtained the sections for 10 body regions of 2 males, and compared 29 simulated sampling designs with the actual one. The results showed that for most regions, a minimum sample size of approximately 20 sections or more were required for the small individual and 15 sections or more for the large individual. We suggested that all paraffin sections of an amphibian skin sample should be prepared for quantification, which may require an intensive sampling effort for certain characteristics. Capillary densities were significantly negatively correlated with sample sizes required. This could be partly explained by a more even distribution of capillaries in regions with higher capillary densities. Such a correlation might contribute to sampling design if it could be confirmed in other amphibians by further studies.
