Evaluación del riego ambiental del insecticida metamidofos en bioensayos con cuatro organismos acuáticos no destinatarios

The aim of this research was to evaluate the ecotoxicological effect of methamidophos using two formulations of different toxicological class [Monofos®, class Ia (extremely dangerous) and Tamaron®, class Ib (highly dangerous)] on four non-target aquatic organisms: bloodworm Chironomus calligraphus (Goeldi, 1905) (Diptera: Chironomidae), black sea urchin Tetrapygus niger Molina, 1782 (Echinodermata: Arbaciidae), neon tetra Paracheirodon innesi (Rabout, 1940) (Osteichthyes: Characidae); and rainbow trout Oncorhynchus mykiss (Walbaum, 1792) (Osteichthyes: Salmonidae). Both methamidophos formulations evidenced a high risk effect on the aquatic environment, finding effects on larvae of C. calligraphus (Class Ia, LC₅₀ at 48 h = 1.32 mg a.i. L^-1 and Class Ib, LC₅₀ at 48 h = 4.5 mg a.i. L^-1), on fertilization of T. niger (Class Ia, IC₅₀ at 1 h = 1423 mg a.i. L^-1 and Class Ib, IC₅₀ at 1 h = 608 mg a.i. L^-1), on P. innesi (Class Ia, LC₅₀ at 96 h = 20.56 mg a. i. L^-1 and Class Ib, LC₅₀ at 96 h = 10.13 mg a.i. L ^-1) and O. mykiss (Class Ib, LC₅₀ at 96 h = 19.12 mg a.i. L^-1). The sequence of sensibility to methamidophos in both formulations was: C. calligraphus > O. mykiss ≈ P. innesi > T. niger. In addition, two sublethal effects were evaluated on P. innesi, immobilization and strange swimming, and finally an increment of opercular movement in O. mykiss. Risk quotients (RQ) indicated in all cases a high risk of methamidophos towards the aquatic environments.