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 characterize 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 measurements. 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.
Highlights
The American bullfrog (Lithobates catesbeianus, Shaw, 1802) belongs to the Ranidae family and is among the most economically and ecologically relevant amphibian species in the world
The mean snout-vent length was 12.6 cm for juvenile individuals, and 14.2 cm for breeder frogs. This variable behaved to weight, in that differences were found between localities (p < 0.001), but not between sexes in juvenile frogs (p = 0.509)
Body size and weight values obtained from juvenile and breeding bullfrogs in the present study, were similar to those reported for those obtained in intensive production systems, and for an introduced wild frog population in Brazil.[20,21]
Summary
The American bullfrog (Lithobates catesbeianus, Shaw, 1802) belongs to the Ranidae family and is among the most economically and ecologically relevant amphibian species in the world This is firstly because it is commonly used in international cuisine (mainly in the United States, France, Belgium, Canada, Italy and Spain,[1] and as it has become one of the 100 most invasive species in the world,[2] as a result of its worldwide expansion for aquaculture development (in over 40 countries).[3] Commercial demand for American bullfrogs increased in the international market from the 1980s, pushing the need to develop and modernize existing production systems.[7] The world bullfrog market has steadily grown since the 1990s,1 with China heading annual production, followed by Singapore and Malaysia, while Brazil and Mexico are fourth and fifth, respectively. Production has increased considerably in several countries, reaching an average annual revenue of $28,141,319 US dollars in 2011.1 Bullfrog farming formally began in Mexico in 1925,4 and has since been introduced in at least 16 states, Michoacán having the higher production yield in the country.[5,6] Since México has become an important bullfrog producer, especially for the American market, reaching over 202 tons and a production value of $18,960,792 Mexican pesos in 2015.4,6
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