Barnacle Larvae of Megabalanus coccopoma (Darwin, 1854) as a Toxicity Test Organisms

Abstract

In Brazil, Marine Ecotoxicology is a retelatively new science with few species routinely used in toxicity tests. Barnacle larvae (Naupliu) have been used for different research groups in the world as test organisms with a variety of methods and applications. These organisms have the advantages of easy obtainment in the field, availability throughout the year and easy manipulation in the lab. The use of these organisms in Brazil is still limited to tests of the activity of anticrustant substances and few work has been done to investigate their sensitivity as test-organisms in Ecotoxicology. This work presents a standard operating procedure to perform toxicity tests with naupliu of the barnacle Megabalanus coccopoma one of the biggest examplers of the subordem Balanomorpha and of great distribution around the Brazilian coast. The sensitivity of naupliu II to Zinc (Zn) was evaluted through mobility and mortality endpoints. Nauplius of the M. coccopoma were obtained from egged lamels of adults and used in 48 hours toxicity tests to assess the effect of zinc sulphate in static experimental conditions; poorly mobile and dead organisms were quantified every 12 hours. On the mobility tests, the EC₅₀ of 0.24 mg L^–1 (Zn) was obtained following 24 hours expousure; whilst the LC₅₀ of 0.27 and 0.22 mg L^–1 (Zn) were obtained following 36 and 48 hours of exposure, respectively. Significant differences were not observed between the EC₅₀ and LC₅₀ values for zinc therefore allowing the development of 24 h mobility and 48 h mortality tests. The EC₅₀; 24 h and LC₅₀; 48 h for zinc demonstrate similar sensitivity between the studied species the mysids Mysidopsis juniae and the copepod Acartia lilljeborgi.