Although pesticides are often discharged into surface waters in pulses as opposed to a sustained release, the effect of episodic pollution events on freshwater crayfish is largely unknown. We monitored change in heart rate and distance moved to assess the response of signal crayfish Pacifastacus leniusculus to short-term exposure to environmentally relevant concentrations of metazachlor (MTZ), terbuthylazine (TER), and thiacloprid (TCL). Crayfish exposed to 20 µg/L of MTZ exhibited a significant increase in mean heart rate and distance moved. Increased heart rate was detected at 118 ± 74 s post-exposure to MTZ. There were no significant differences in mean heart rate and distance moved in crayfish exposed to 6 µg/L of TCL and 4 µg/L of TER. A significant correlation between heart rate and distance moved was found in all exposed groups. These results suggest that pulse exposure to MTZ impact crayfish physiology and behavior during short-term period. With pulse exposure to TCL and TER, crayfish not exhibiting a locomotor response may continue to be exposed to lower, but potentially harmful, levels of pollutants. Evidence of the impacts of pesticide pulse at environmentally relevant concentrations on crayfish is scarce. Further study is required to determine the ecological effects of such events on freshwater crayfish.

• Keywords
• Freshwater invertebrate, Locomotor activity Metazachlor, Short-term exposure, Terbuthylazine, Thiacloprid,
• MeSH
• Water Pollutants, Chemical * toxicity   MeSH
• Pesticides * toxicity   MeSH
• Astacoidea MeSH
• Heart Rate MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Water Pollutants, Chemical * MeSH
• Pesticides * MeSH
• thiacloprid MeSH Browser

The effects of the herbicide metazachlor and its major metabolite metazachlor OA at two concentrations, including environmentally relevant concentrations of metazachlor (0.0115 µmol/l and 0.0790 µmol/l) and metazachlor OA (0.0117 µmol/l and 0.0805 µmol/l), respectively, were evaluated on early ontogeny, growth, behaviour, oxidative stress, antioxidant enzyme levels, histology, and mortality of marbled crayfish Procambarus virginalis. Both tested concentrations of metazachlor and metazachlor OA were associated with significantly lower growth and delayed ontogenetic development compared to controls. Exposure of metazachlor at 0.0115 µmol/l and metazachlor OA at 0.0117 µmol/l and 0.0805 µmol/l resulted in significantly lower activity of total superoxide dismutase (SOD), catalase (CAT), glutathione s-transferase (GST), glutathione reductase (GR), and reduced glutathione (GSH) compared with control and resulted in gill anomalies ranging from wall thinning to focal disintegration of branchial structure. Metazachlor at the environmentally relevant concentration of 0.0790 µmol/l was associated with significant alterations of crayfish distance moved and walking speed. The potential risk associated with metazachlor use in agriculture related to effects on non-target aquatic organisms.

• MeSH
• Acetamides metabolism   toxicity   MeSH
• Antioxidants metabolism   MeSH
• Water Pollutants, Chemical toxicity   MeSH
• Ecotoxicology MeSH
• Embryo, Nonmammalian drug effects   MeSH
• Glutathione metabolism   MeSH
• Glutathione Reductase metabolism   MeSH
• Hepatopancreas drug effects   pathology   MeSH
• Herbicides metabolism   toxicity   MeSH
• Locomotion drug effects   MeSH
• Oxidative Stress drug effects   MeSH
• Astacoidea drug effects   embryology   growth & development   metabolism   MeSH
• Superoxide Dismutase metabolism   MeSH
• Gills drug effects   pathology   MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Acetamides MeSH
• Antioxidants MeSH
• Water Pollutants, Chemical MeSH
• Glutathione MeSH
• Glutathione Reductase MeSH
• Herbicides MeSH
• metazachlor MeSH Browser
• Superoxide Dismutase MeSH