Palabras clave: Dafniidae, metal pesado, toxicidad aguda, relevancia ecológica RESUMEN Los cladóceros han sido utilizados como organismos de prueba para evaluar el efecto adverso de contaminantes en sistemas acuáticos. Daphnia magna y Ceriodaphnia dubia están entre los más utilizados en pruebas de toxicidad acuática. Sin embargo, son poco representativos para evaluar ecosistemas acuáticos tropicales. Ceriodaphnia cornuta es un organismo común en aguas tropicales que tolera variaciones de temperatura, distribuyéndose ampliamente en diversos humedales. En este estudio, evaluamos la sensibilidad de C. cornuta a los metales pesados: plomo, cobre, cadmio, aluminio, y cromo, a través de pruebas de toxicidad letal. Los valores nominales y reales de Concentración Letal 50 (CL50) a 48 h obtenidos para plomo, cadmio, aluminio, cobre y cromo fueron (0.05, 0.06), (0.031, 0.027), (1.58, 1.54), (0.02, 0.02) y (1.12, 1.16) mg/L, respectivamente. La mayor sensibilidad de este cladócero ocurrió en bajas concentraciones de cobre, cadmio y plomo, mientras que es poco sensible al aluminio. Los valores de CL50 a 48 h para C. cornuta expuesta a cobre, cadmio y plomo son menores a lo reportado con otras especies de cladóceros usadas en pruebas de toxicidad letal. Lo anterior muestra una mayor sensibilidad que D. magna y C. dubia, incluso es comparable a lo reportado para otras especies de cladóceros tropicales. En conclusión, C. cornuta puede ser considerada como un organismo de prueba adecuado para el monitoreo de ecosistemas costeros tropicales contaminados con metales como cobre, cadmio y plomo presentes en el Golfo de México.Key words: Daphniidae, heavy metal, acute toxicity, ecological relevance ABSTRACT Cladocerans have been used as test organisms to assess the adverse effects of pollutants in aquatic systems. Both Daphnia magna and Ceriodaphnia dubia are among the most commonly cladocerans used in aquatic toxicity tests. However, they are inadequate to assess tropical aquatic ecosystems. Ceriodaphnia cornuta is a common organism in tropical waters which tolerates variations in temperature, and is widely distributed Rev. Int.

<p>Arroyo Moreno (AM) is an estuarine water flow located between Boca del Río and Medellin municipalities from Veracruz State; although this estuarine habitat is situated in a state natural reserve, their environmental conditions had been altered in last decades by anthropogenic activities, which had caused changes on biotic communities including fishes. The aim of this contribution was to describe the temporal variation of fish species composition from Arroyo Moreno; an updated list of fish species was compiled for this estuarine channel, this list was made with ethnographic information provided by local fisherman using surveys, fish species catalogues, previous publications and complemented with cast net samplings. Sixty-two fish species were recorded, of these 18 were collected directly for us, another 41 species were identified by surveyed fishermen; the most abundant ecological guilds were marine temporary, freshwater temporary, and marine migrant species. With the historical fishermen’s information was inferred than both fish species richness, abundance and size had diminished noticeably in commercial fish species mainly, this outcome was related by the fishermen to the use of estuarine channel as drainage attributed to urban development in the zone.</p>