Tolerance response to ammonia and nitrite in hatchlings paralarvae of <Emphasis Type="Italic">Octopus vulgaris</Emphasis> and its toxic effects on prey consumption rate and chromatophores activity

Ammonia and nitrite are among the most important water quality parameters. The aim of this study was to determine the acute toxicity of unionized ammonia and nitrite on newly hatched Octopus vulgaris paralarvae. Concretely, survival, feeding and chromatophore activity were examined under different NH₃ and NO₂ ⁻ concentrations. The median lethal concentration (LC 50) determined for 24 h was 10.7 ppm for NH₃ and 19.9 ppm for NO₂ ⁻. Based on these results, a concentration range was chosen to test the effect of this environmental contaminants in feeding and chromatophore activity (range between 2.5 and 20 ppm for feeding and 10 and 30 ppm for chromatophore activity), resulting in modifications in both parameters. In fact, a significant decrease (P < 0.05) in Artemia nauplii consumption by the paralarvae was observed with an increase in NH₃ and NO₂ ⁻. Similarly, the chromatophore activity was also affected by concentration of these contaminants, with decreasing response (P < 0.05) when submitted to stressful situations, as the ammonia and nitrite concentration was increased.