Systemic rhabdomyolysis induced by venom of freshwater stingrays Plesiotrygon iwamae and Potamotrygon motoro (Chondrichthyes-Potamotrygonidae) from the Amazon Basin.

Injuries caused by freshwater stingrays are characterized by intense pain and pathological changes at the lesion site, including oedema, erythema and, in most cases, necrosis. In this study, the systemic myotoxic activity induced by mucus extracts from the dorsal region and stinger of the stingrays Plesiotrygon iwamae and Potamotrygon motoro was described, analysed and quantified. Twenty-four hours after injection of 400 μg of the extracts into the gastrocnemius muscle of mice, the following effects were observed: coagulative necrosis of the muscle tissue, muscle fibre regeneration and the presence of inflammatory infiltrates, including neutrophils, macrophages, and a reduced number of eosinophils and lymphocytes. These changes were also observed, although to a lesser extent, in the gastrocnemius muscles of the contralateral limbs, demonstrating that the extracts from the two species could induce systemic rhabdomyolysis. Based on morphometric analysis, it was observed that the stinger extract of P. motoro was more potent in inducing local and systemic myotoxic activity, followed by the dorsal extract from P. motoro and stinger and dorsal extracts from P. iwamae, which induced similar effects.