Involvement of oxygenase confers higher resistance to neonicotinoid insecticides in estuarine resident sand shrimp Crangon uritai than in kuruma prawn Penaeus japonicus and mysid Americamysis bahia

Globally, neonicotinoid contamination in aquatic environments, including estuarine areas, is a prevailing environmental concern. The estuarine resident marine crustacean sand shrimp Crangon uritai was previously found to have a higher tolerance to neonicotinoids than the marine crustaceans kuruma prawn Penaeus japonicus and mysid Americamysis bahia. Based on these findings, we aimed to explore the mechanisms underlying their differences in insecticide sensitivity. We hypothesized that differences in the structures of their nicotinic acetylcholine receptors (nAChRs) and/or the involvement of a metabolizing enzyme may confer sand shrimp resistance to neonicotinoids. No obvious differences were found in the amino acid residue (position 81) of the loop D region of the nAChR β-subunit among the three crustaceans. A synergistic toxicity bioassay was used to explore candidate metabolizing enzymes, esterase, glutathione S-transferase, and oxygenase. The three species were exposed to two neonicotinoids (acetamiprid and clothianidin) at concentrations equivalent to 1/15–1/10 of 96-h LC50 values and synergists (inhibitors of metabolizing enzyme) or combinations of both. Treatments with the oxygenase inhibitor and the neonicotinoids resulted in increased mortality in sand shrimps but not in kuruma prawns or mysids. Consequently, it was determined that oxygenase may explain the higher resistance of the sand shrimp to neonicotinoid insecticides.