ABSTRACT
Crude electronic waste (e-waste) recycling has been banned due to the serious environmental pollution it caused, leaving many abandoned e-waste sites. However, information on the current levels and associated ecological risks of e-waste-derived contaminants such as polychlorinated biphenyls (PCBs) in e-waste site is limited. Wild fish, because they can accumulate high pollutant levels, are suitable indicators for environmental pollution monitoring and has been widely employed as biomonitoring. In this study, we investigated the changes in the levels and profiles of PCBs in a wild fish species, the northern snakehead (Channa argus), before (2009) and after (2016) the ban of crude e-waste recycling from a typical e-waste recycling site in South China. The mean total PCB concentration in the northern snakehead sampled in 2016 (343 ng/g ww) declined by 75% compared with that (1410 ng/g ww) in 2009. The contributions of less chlorinated congeners (tri-CBs and tetra-CBs) in the northern snakehead tended to decrease over the years, indicating that the lighter congeners are more easily eliminated than the heavier ones in the environment. Our findings suggested no fresh PCB input in these years, as well as the positive impacts of laws and regulations on the prohibition of e-waste recycling. The ecological risk assessment suggested that PCB exposure may have median to high risks to the wild fish and fish-eating wildlife that inhabit the e-waste site, even after the ban of crude e-waste recycling activities.
Subject(s)
Electronic Waste , Polychlorinated Biphenyls , Animals , Polychlorinated Biphenyls/analysis , Environmental Monitoring , China , FishesABSTRACT
Insects perceive dangerous or attractive chemicals in the environment (such as the presence of predators, food or mates) through their olfaction and gustation. This leads to host searching, mate finding and other behaviors that are critical for insect survival. These vital activities are mediated by many chemosensory receptor proteins, including odorant receptors (ORs), gustatory receptors (GRs) and ionotropic receptors (IRs). Trichogramma japonicum Ashmead (Hymenoptera: Trichogrammatidae) is a commonly used egg parasitoid for controlling lepidopteran pests in rice fields. To reveal the roles of its olfactory and gustatory systems in biological control, we systematically analyzed major chemosensory receptor genes from T. japonicum. Through transcriptomic analyses of male and female heads, we found that the differentially expressed genes (DEGs) were mainly related to chemosensory functions, and there were more chemosensory-related genes expressed in female heads than male heads, which may be related to the need for females to search for their hosts or sense male pheromone. Furthermore, we identified 66 chemosensory receptor genes, including 51 ORs, seven IRs and eight GRs, that were most closely relate to those of other hymenopteran species according to the results of both Blast best-hit and phylogenetic analyses. The tissue expression profile showed that 65 of the 66 chemosensory receptors were highly expressed in the heads, suggesting their putative roles in olfaction and gustation. In addition, the sex-specific expression patterns suggested their potential functions in host-seeking or mate sensing behaviors. This study may provide base for further understanding the olfactory and gustatory systems of T. japonicum and increasing its efficiency in pest control in the future.
