Phototaxis in aquatic invertebrates: possible use in ecotoxicity tests.

A series of experiments has been carried out aimed at (i) a deeper study of the phototaxis of some aquatic invertebrates and (ii) its possible use in ecotoxicity tests. For the first point the phototaxis of the nauplii of Artemia salina was examined: through tests carried out under different conditions, it was observed that a marked complex response to light existed, which led to a subdivision between individuals with different phototactic response, mainly depending on the density of the nauplii, on light intensity, and on spectral composition. The second point has been analyzed with A. salina, Daphnia magna, and Aëdes aegypti. For the first species it must be stressed that in ecotoxicity tests carried out with nauplii of A. salina one should bear in mind the complexity of their phototactic response. With D. magna and A. aegypti a simple pvc apparatus connected with optic fibers and set up on a microscope was used. The result is marked and easily observable; therefore, it will be possible in the future to perform easily tests with toxic substances which are important in ecotoxicology.