Lethal and sublethal toxicity of sodio phosphate dibasic and effects in gills and behaviour of fry on the goodeid fish Skiffia multipunctata

Abstract

Organic phosphate is an essential compound involved on several metabolic processes, and it is a component of biomolecules of great relevance (proteins, DNA, RNA and ATP). In the aquatic ecosystems, it is necessary for the development of trophic chains. However, phosphates derivated from detergents and fertilizers are some of the main contaminants in water bodies. Nevertheless, the deleterious effects of the phosphates on the morphophysiology of aquatic organisms, particularly in fishes, have not been documented. For this reason, the present work determined the negative effects that the sodium phosphate caused on the survival, swimming behavior, response to the presence of food and gill morphology of the fry of Skiffia multipunctata (Pellegrin, 1901). This species is endemic to the lower Lerma basin and to the upper Santiago basin (both in the Western central part of Mexico), and it is considered threatened. Results showed that organisms exposed to the phosphate-exhibited lethargy, preference towards swimming near the bottom of the aquarium, gasping, spiral swimming and crashing against the walls of the aquarium. Histological preparations of the gills showed lamellar hyperplasia, cell pyknosis and lamellar fusion. The effects of these alterations depended on the phosphates concentration. The gill alterations coincided with the preference of the fish towards swimming near to the surface and bottom of the aquarium and with the decrease in the number of active fish during feeding. This constitutes strong evidence that behavioral changes are related to the failure of the oxygen capture in the gill tissue. These finds emphasize the importance of researching the negative effects that high concentrations of phosphates can cause on sensitive and endemic species such as S. multipunctata.