First occurrence of parasitic isopod ( <i>Braga nasuta</i> , Schioedte &amp; Meinert, 1881) on ornamental fish in Europe

Abstract Parasitic crustaceans represent a significant threat to both freshwater and marine aquaculture, with several families capable of inducing severe diseases with high mortality rates and therefore significant economic losses. Among them, isopods of the genus Braga (Cymothoidae) are haematophagous parasites of neotropical fish, causing anaemia, tissue damage, and mortality. Braga nasuta , endemic to Brazil, has been reported from various hosts, including ornamental species exported worldwide. During routine examination of imported cardinal tetra ( Paracheirodon axelrodi , Schultz, 1956), the authors detected that one of the fish harbored an adult male isopod (∼6.21 mm long, 2.66 mm wide) attached anterior to the dorsal fin. Based on morphological identification, the parasite was identified as Braga nasuta . No secondary pathogens were observed in affected fish. Given the global trade in ornamental species, the introduction of B. nasuta into non-native regions underscores the importance of quarantine and parasite monitoring. While the potential ability of this parasite to establish populations in Europe requires further studies, vigilance is warranted to prevent potential spread and ecological impact. In this study, the authors document the first occurrence of B. nasuta in Europe, detected on a cardinal tetra ( P. axelrodi ) imported to a Hungarian public aquarium.