Universidade Estadual do Maranhão

The present study aimed to report monogenoids parasitizing the gills of two species of piranhas from the state of Maranhão, Brazil: Pygocentrus nattereri Kner, and Serrasalmus rhombeus (Linnaeus). Fifty specimens of P. nattereri were caught in the Lake "Grande" in the municipality of São Bento, and 50 specimens of S. rhombeus were caught in the main channel of the Pericumã River, municipality of Pinheiro. Fourteen species of dactylogyrids were found parasitizing the gills of P. nattereri and S. rhombeus. Of the 14 species identified, 11 were found in P. nattereri: Amphitecium calycinum Boeger & Kritsky, 1988, Amphitecium camelum Boeger & Kritsky, 1988; Amphitecium falcatum Boeger & Kritsky, 1988; Amphitecium junki Boeger & Kritsky, 1988; Amphithecium sp.; Anacanthorus sp. 1; Anacanthorus jegui Van Every & Kritsky, 1992; Anacanthorus mesocondylus Van Every & Kritsky, 1992; Anacanthorus reginae Boeger & Kritsky, 1988; Anacanthorus sciponophallus Van Every & Kritsky, 1992 and Anacanthorus thatcheri Boeger & Kritsky, 1992. Five species were found in S. rhombeus: Am. calycinum; Am. falcatum; Anacanthorus amazonicus Van Every & Kritsky, 1992; A. maranhensis n. sp. and Notozothecium sp. Anacanthorus sp. 1 differs from its congeners by the morphology of the MCO, which is a flat tube with sclerotized walls and pointed terminations at both ends. Anacanthorus maranhensis n. sp. differs from its congeners by the morphology of the MCO, which is a trough-shaped tube. This study increases the number of reported dactylogyrids from P. nattereri to 28, and to 26 for S. rhombeus.

The red palm mite, Raoiella indica Hirst (Acari: Tenuipalpidae), is a major pest of coconut, banana and ornamentals in tropical America. Essential oils have proven bioactivity against pest arthropods and are highlighted for its potential in sustainable pest control. In this study, we evaluated the toxicity and sublethal effects of the essential oil extracted from Varronia curassavica Jacq. (Boraginaceae) [syn. Varronia (formerly Cordia) verbenacea DC] on R. indica. The essential oil from V. curassavica (accession VCUR 404) comprised 28 chemical constituents, with ar-turmerone being the predominant component. The oil exhibited high acute toxicity to adult R. indica, with a median lethal concentration (LC₅₀) of 1.9 mg/mL. In addition to toxicity, the oil significantly reduced the mite population growth rate, survival, and egg hatchability. Interestingly, despite its lethal and sublethal effects, adult mites showed a marked preference for oil-treated areas in a laboratory two-choice bioassay, suggesting an attractant-mediated mechanism that may lead to mortality. Overall, our findings highlight the essential oil of V. curassavica as a promising candidate for the development of environmentally sound strategies for the management of R. indica.