Commercial product-derived microplastics based on polypropylene and polylactic acid and their harmful effects on the sea urchin Paracentrotus lividus (Lmk) embryos: Morphological and gene expression analysis

Plastics provide a range of benefits in our society, even if waste plastics are representing a worrying issue for the environment. In addition, various additives, i.e., chemical substances added to plastic polymers to enhance their properties, create complications in their lifecycle. In fact, inappropriate use and recycling of plastics inevitably leads to the release of toxic substances. In this work we analyzed the possible toxic effects of microplastics obtained from commercial cups made from polypropylene (PP) and from the biodegradable polymer poly (lactic acid) (PLA), on the sea urchin Paracentrotus lividus (Lmk) embryos. We exposed eggs of P. lividus to microplastics derived from PLA and PP cups for 10 ​min at increasing concentrations. The eggs were then fertilized and the embryonic development was followed until the pluteus stage at 48 ​h post fertilization (hpf). Our results showed that neither PLA nor PP microplastics had a measurable effect on fertilization, but both affected the first mitotic division, induced delay of embryonic development with many embryos still at blastula and gastrula stages at 48 hpf, and caused malformations in embryos that reached the pluteus stage. Moreover, the expression level of several genes involved in different functional pathways linked to stress and detoxification responses, development, differentiation and skeletogenesis were followed by Real time qPCR, with the aim of identifying the molecular targets of PLA and PP. These morphological effects were a result of the up-regulation of most of the genes analyzed and used by the embryos to react to the detrimental effects induced by plastics. Our findings highlighted the important issue of plastic additives, which can be released during the various recycling and recovery processes of contaminated ecosystems.