Antifouling Compounds Endangering Marine Invertebrates Reproduction

Abstract

EditorialReproduction and embryo development of marine animals occur in the sea water and are processes very sensitive to substances present in the environment that come from industrial and agricultural activities. These compounds are collectively known as xenobiotics due to their extra-environmental origin. Among xenobiotics present in the sea water, a relevant role is played by the anti-fouling compounds. These are used to prevent settlement and growth of organisms on submerged structures of vessels and ships that otherwise should create serious problems of speed slow down.In the 60', chemical industries designed paints based on tin metallic compounds named organotines that included tributyltin (TBT) and triphenyltin (TPT). These biocides demonstrated to be very efficacious in impeding the attachment of marine organisms on the ships surface, however a serious toxic side effect exerted on the wild marine species has emerged during the last decades [1]. Numerous ecotoxicological studies clearly indicated that organotines are highly toxic for sea life since they persist in the water, being recycled from the sediments and entering the food chain. The interference with the endocrine system of marine invertebrates and vertebrates, even at low concentrations, may generate high risk of reproductive disorders up to threaten the survival of the species In particular, the exposure to TBT was clearly associated to the phenomenon of imposex, i.e. an irreversible induction of male sex characteristics on females marine snails [2]. For this reason, the International Maritime Organization Although not all the countries adhered to this ban, chemical industries have started to formulate new friendly antifouling compounds as possible alternatives to organotines. Among them, the organic booster biocides diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) [4] and chlorothalonil are the most widely employed. Since their recent application and release in the environment, no many data are currently available on their toxicity and in particular on their impact on the main parameters and events of reproduction such as gametes physiology, fertilization, and early embryo development of marine species. Our group has performed a comparative investigation on the effects of TBT, diuron and chlorothalonil, as old and new generation antifouling biocides, and to do this it was chosen a very peculiar approach that is the study of the oocyte plasma membrane by looking at the ion currents underlying the reproductive events of the marine invertebrate Ciona intestinalis (ascidians).The use of this model is particularly challenging since ecotoxicological studies used for decades the sea urchin embryo survival to test environmental toxicity, but it was not considered to test also the basic process of fertilization.In our studies, surprisingly we discovered a common action of the three biocides in reducing the sodium currents of the virgin oocytes. This is an alarming view since, in the past, it was shown a clear role of these currents in driving a correct...