Microplastic is a growing concern as an environmental contaminant as it is ubiquitous in our ecosystems. Microplastics are present in terrestrial environments, yet the majority of studies have focused on the adverse effects of microplastics on aquatic biota. We hypothesized that microplastic ingestion by a terrestrial insect would have localized effects on gut health and nutrient absorption, such that prolonged dietary microplastic exposure would impact growth rate and adult body size. We further hypothesized that plastic form (fibres vs. beads) would influence these effects because of the nature of gut-plastic interactions. Freshly hatched tropical house crickets (Gryllodes sigillatus) were fed a standard diet containing different concentrations of either fluorescent polyethylene microplastic beads (75–105 μm), or untreated polyethylene terephthalate microfibers (< 5 mm) until they died or reached adulthood (approximately 8 weeks). Weight and body length were measured weekly and microplastic ingestion was confirmed through fluorescence microscopy and visual inspection of the frass. While, to our surprise, we found no effect of polyethylene bead ingestion on growth rate or final body size of G. sigillatus, females experienced a reduction in size and weight when fed high concentrations of polyethylene terephthalate microfibers. These results suggest that high concentrations of polyethylene beads of the 100 μm size range can pass through the cricket gut without a substantial negative effect on their growth and development time, but high concentrations of polyethylene terephthalate microfibers cannot. Although we report the negative effects of microplastic ingestion on the growth of G. sigillatus, it remains uncertain what threats microplastics pose to terrestrial insects.
Swede midge (Contarinia nasturtii Kieffer) is an invasive, economic pest of canola (Brassica napus L.) that threatens production throughout Canada. Swede midge has up to four overlapping generations, placing canola at risk of multiple infestations in the field. The relationship between single and multiple swede midge infestations at different canola stages, and the resulting impacts on yield, are unknown. Laboratory experiments were conducted to evaluate the impact of single and multiple infestations of swede midge on four plant stages of canola: three-leaf, seven-leaf, primary bud, and secondary bud. Previously, the seven-leaf and primary bud stages were considered vulnerable to swede midge, but we determined that the secondary bud stage is also vulnerable. Evidence of compensation by canola in response to herbivory by swede midge was discovered. Compensation occurred mainly through increased production of tertiary racemes and pods and was maximized with exposure of 4.5–6.5 female midges per plant. Although compensation may increase potential yield, it also results in uneven crop maturation resulting in delayed harvest and yield loss. Consequently, to prevent delays in maturation and harvest, insecticides should be applied before these densities are reached.
Microplastic is a growing concern as an environmental contaminant as it is ubiquitous in our ecosystems. Microplastics are present in terrestrial environments, yet the majority of studies have focused on the adverse effects of microplastics on aquatic biota. We hypothesized that microplastic ingestion by a terrestrial insect would have localized effects on gut health and nutrient absorption, such that prolonged dietary microplastic exposure would impact growth rate and adult body size. We further hypothesized that plastic form (fibres vs. beads) would influence these effects because of the nature of gut-plastic interactions. Freshly hatched tropical house crickets (Gryllodes sigillatus) were fed a standard diet containing different concentrations ofeither fluorescent polyethylene microplastic beads (75-105 μm), or untreated polyethylene terephthalate microfibers (<5 mm) until they died or reached adulthood (approximately 8 weeks). Weight and body length were measured weekly and microplastic ingestion was confirmed through fluorescence microscopy and visual inspection of the frass. While, to our surprise, we found no effect of polyethylene bead ingestion on growth rate or final body size of G. sigillatus, females experienced a reduction in size and weight when fed high concentrations of polyethylene terephthalate microfibers. These results suggest that high concentrations of polyethylene beads of the 100 μm size range can pass through the cricket gut without a substantial negative effect on their growth and development time, but high concentrations of polyethylene terephthalate microfibers cannot. Although we report the negative effects of microplastic ingestion on the growth of G. sigillatus, it remains uncertain what threats microplastics pose to terrestrial insects
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