Analysis of the effects of co-exposure to antibiotics and cadmium on sea urchin embryos

In order to understand the mechanisms of responses to changes in the physical and chemical environment, as well as the mechanisms of developmental pathways, we investigated by RT-qPCR assays and light microscopy observations the impact of antibiotics and cadmium in P. lividus sea urchin embryos. In particular we inspected development and biomarkers for free radical damage and apoptosis. During development embryos were exposed to an antibiotic mix (Ab mix, usually added to sea urchin cultures) or to sulfamethoxazole/trimethoprim mix (TMP/SMX, usually added to aquacultures) and/or levels of 10-5, 10-4, 10-3 M CdCl2. Even though treatment with TMP/SMX apparently did not affect development, it stimulated a remarkable molecular response to oxidative stress. Moreover, when embryos were exposed to TMP/SMX and CdCl2, even development was seriously impaired and the antioxidant defense was blocked. On the other hand, Ab mix and Cd co-treatment made the cadmium effect on development worse, but the antioxidant molecular defense was unchanged, rising the possibility that another stress pathway is involved. This study leads to the conclusion that co-exposure to antibiotics and cadmium induces synergistic effects on sea urchin embryos. Thus, in cadmium contaminated areas, antibiotic discharge can be an important environmental factor which might play an important role in survival of P. lividus populations.