EFEITO AGUDO DO EXTRATO DE MACROALGA (Kappaphycus alvarezii), EM JUVENIS DE GUPPY (Poecilia reticulata)

Abstract

This study aimed to evaluate the acute toxicological effects of the crude extract of the macroalga Kappaphycus alvarezii on juveniles of Poecilia reticulata (guppy), through toxicity tests, histological analysis, and monitoring of the water's physicochemical parameters. Five extract concentrations (4%, 6%, 8%, 10%, and 12%) and a control group were tested, with 20 animals per treatment (10 per replicate), exposed for 96 hours. The LC₅₀ was estimated for 24, 48, 72, and 96 hours, with the LC₅₀-96h determined at 4.17% (CI: 3.54–4.90%). Survival was analyzed using Kaplan-Meier curves with Bonferroni correction, revealing statistically significant differences between treatments. Progressive histological lesions were observed in the gills (edema, lamellar fusion, hypertrophy) and liver (vacuolization, necrosis, cellular disorganization), especially from the 6% concentration onward. The results indicate that K. alvarezii extract can present toxic effects even at relatively low concentrations, highlighting the importance of species-specific evaluations before its application in aquaculture systems. This study provides relevant information for the sustainable use of marine macroalgae as functional inputs in ornamental fish farming and in more ecological production systems.