AQUATIC ACOUSTIC NOISE: BEHAVIORAL AND MOLECULAR RESPONSES IN ECHINODERMS, THE CASE OF A. LIXULA (LINNAEUS, 1758) SEA URCHINS

Abstract

Anthropic noise is considered a real pollutant, in particular the submarine noise. The impact on biodiversity is not yet sufficiently understood. Further research is needed to evaluate any negative effects. The noises associated with anthropogenic activities are increasing: shipments, seismic surveys, sonar, recreational rowing and future mineral extraction activities from ocean depths (DSM). These noises are having an impact on the welfare of many marine species. The understanding of the effects on biodiversity could be important for the creation of guidelines, laws or rules for the most environmentally sustainable exploitation of natural resources. Our study aims to investigate the motility, biochemical and molecular responses of Arbacia lixula exposed to an acoustic stimulus produced by anthropogenic activities and perhaps perceptible by invertebrates. The animals were divided into a control tank and experimental tank. The specimens were exposed to sonic stress for 3 hours after which biological sampling was performed. The sonic stress used was a linear sweep from 100 to 200 kHz emitted every 1 second. The Sound Pressure Level ranges between 173 and 181 dBrms (re 1μPa), with a peak at 150 kHz. To measure the motility, on the top of the tanks two cameras were placed to make photo each 8 seconds during acoustic stimulus. The bottom of the tanks were divided virtually by squares and the vertical walls were divided by two quote. At each photo we assessed the position of the animals and count the number of squares/levels crossed comparing to the precedent photo. In this way we obtained the motility of the specimens in the three directions (cm/s). After three hours of stimulus projection, the sea urchins were captured and the coelomatic fluid was extracted. The protein concentration and the enzymatic activities of esterase, phosphatase, catalase and peroxidase were measured on the celomocytes and on the supernatant of the celomatic fluid. The gene expression of HSP70 and HSP90 with RT-PCR was evaluated on celomocytes. Exposure to this type of noise produced a significant changing in motility and an increase in the expression of HSPs gene, more so for HSP70. No statistical difference was observed in the extent of enzymatic activities and protein concentration. The results obtained indicate that this type of acoustic stimulus has effects on the behavior and on the gene expression of HSPs of individuals of Arbacia lixula.