38 research outputs found
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Developmental effects of micro- and nanoscale tire particles and recycled rubber on zebrafish
Plastics have become an essential part of everyone lives, found in almost every product made today. Tires only make up a fraction of these products but as their use increasing so does the microplastics that flake off. Many studies have evaluated the toxic effects of tire particles on aquatic environments by testing the leachate they give off in water. However, no studies to date have investigated the specific effects of micro- and nanoscale tire particles themselves. With the increase of many toxic particulates being introduced into the ocean and other aquatic environments, there is serious concern as to how it could affect the life in these areas. This study looked at the effects of micro (1-20 μm) and nano-sized (<1 μm) tire and recycled rubber particles on developing zebrafish embryos. Zebrafish (Danio rerio) were selected for these studies because they are vertebrates that make for a efficient and cheap ecotoxicity indicator for potential impacts on fish in aquatic systems while providing insight into potential negative human health effects. Previous studies reveal that tire particles can cause mortality and sub-lethal effects in multiple fish species, while recycled rubber does not show any overt toxicity but can release polycyclic aromatic hydrocarbons (PAHs), some of which are known toxicants. In our studies, the highest mortality was caused by exposure to nanoscale tire particles (TPs). Micro-sized particles showed limited mortality and sub-lethal effects. Leachate exposures resulted in varying mortality occurrence but nothing that was significant, although, the leachate did show the most sub-lethal effects. These effects occurred at concentrations well above levels currently identified in environmental samples; however, the sampling techniques currently used in environmental sampling overlook any particles in the nanoscale range. Given that environmental concentrations are completely unknown, it is important to understand the levels at which micro- and nanoscale TPs and their leachates can elicit adverse outcomes for exposed organisms
Recommended from our members
Developmental effects of micro- and nanoscale tire particles and recycled rubber on zebrafish
Plastics have become an essential part of everyone lives, found in almost every product made today. Tires only make up a fraction of these products but as their use increasing so does the microplastics that flake off. Many studies have evaluated the toxic effects of tire particles on aquatic environments by testing the leachate they give off in water. However, no studies to date have investigated the specific effects of micron and nanoscale tire particles themselves. With the increase of many toxic particulates being introduced into the ocean and other aquatic environments, there is serious concern as to how it could affect the life in these areas. This study looked at the effects of micro (1-20 μm) and nano-sized (<1 μm) tire and recycled rubber particles on developing zebrafish embryos. Zebrafish (Danio rerio) were selected for these studies because they are vertebrates that make for an efficient and cheap ecotoxicity indicator for potential impacts on fish in aquatic systems while providing insight into potential negative human health effects. Previous studies reveal that tire particles can cause mortality and sub-lethal effects in multiple fish species, while recycled rubber does not show any overt toxicity but can release polycyclic aromatic hydrocarbons (PAHs), some of which are known toxicants. In our studies, the highest mortality was caused by exposure to nanoscale tire particles (TPs). Micron-sized particles showed limited mortality and sub-lethal effects. Leachate exposures resulted in varying mortality occurrence but nothing that was significant, although, the leachate did show the most sub-lethal effects. These effects occurred at concentrations well above levels currently identified in environmental samples; however, the sampling techniques currently used in environmental sampling overlook any particles in the nanoscale range. Given that environmental concentrations are completely unknown, it is important to understand the levels at which micro- and nanoscale TPs and their leachates can elicit adverse outcomes for exposed organisms.Key Words: Zebrafish, tire particles, nano, micro, fractionat
A Molecular Phylogeny of the Chalcidoidea (Hymenoptera)
Chalcidoidea (Hymenoptera) are extremely diverse with more than 23,000 species described and over 500,000 species estimated to exist. This is the first comprehensive phylogenetic analysis of the superfamily based on a molecular analysis of 18S and 28S ribosomal gene regions for 19 families, 72 subfamilies, 343 genera and 649 species. The 56 outgroups are comprised of Ceraphronoidea and most proctotrupomorph families, including Mymarommatidae. Data alignment and the impact of ambiguous regions are explored using a secondary structure analysis and automated (MAFFT) alignments of the core and pairing regions and regions of ambiguous alignment. Both likelihood and parsimony approaches are used to analyze the data. Overall there is no impact of alignment method, and few but substantial differences between likelihood and parsimony approaches. Monophyly of Chalcidoidea and a sister group relationship between Mymaridae and the remaining Chalcidoidea is strongly supported in all analyses. Either Mymarommatoidea or Diaprioidea are the sister group of Chalcidoidea depending on the analysis. Likelihood analyses place Rotoitidae as the sister group of the remaining Chalcidoidea after Mymaridae, whereas parsimony nests them within Chalcidoidea. Some traditional family groups are supported as monophyletic (Agaonidae, Eucharitidae, Encyrtidae, Eulophidae, Leucospidae, Mymaridae, Ormyridae, Signiphoridae, Tanaostigmatidae and Trichogrammatidae). Several other families are paraphyletic (Perilampidae) or polyphyletic (Aphelinidae, Chalcididae, Eupelmidae, Eurytomidae, Pteromalidae, Tetracampidae and Torymidae). Evolutionary scenarios discussed for Chalcidoidea include the evolution of phytophagy, egg parasitism, sternorrhynchan parasitism, hypermetamorphic development and heteronomy