Phenotypic variation in american bullfrogs (Lithobates catesbeianus) bred under intensive systems in Mexico: A preliminary report

Abstract

Commercial bullfrog farming has increased steadily in Mexico from 1925 to satisfy both the national and international markets. However, intensive production systems are still scarce, and there is a need for information to help further advance their development. Therefore, this study aimed to char-acterize and compare morphometric and physiological traits of bullfrogs bred under intensive culture systems. Three-year-old breeding adults (n = 100) from five farms in three different states, and one-year old juveniles (n = 60) from two of these locations, were used in the study. The scaled mass index (SMI) was calculated by considering body weight and snout-vent length mea-surements. Hematocrit and white blood cell concentrations were determined in juveniles, and a leukocyte profile was established. Eight linear (based on measurements from photographs of the skull), plus one geometric, variables, were used for morphometric analyses. Results show that the SMI did not vary between localities or gender in juvenile frogs, while differences were found both between sexes (p < 0.026) and between farms (p < 0.001) in adult frogs. Hematocrit and neutrophil concentrations in juvenile individuals also differed between localities. Linear and geometric morphometric analyses in juvenile frogs showed differences between sexes (p < 0.001) and between localities (p < 0.001), the latter suggesting the existence of at least two morphotypes of this species. This study presents relevant information to help advance bullfrog farming in Mexico.