The impacts of sublethal neonicotinoid exposure on shrimp

Peter Joseph Butcherine

doi:10.25918/thesis.169

The widespread use of systemic neonicotinoid insecticides in agriculture has resulted in the unintended contamination of aquatic environments at concentrations that could impact aquaculture stock. The high toxicity of neonicotinoids to non-target aquatic insects and crustaceans has been documented; however, the effects on commercial shrimp species are unclear. This thesis aimed to examine the impacts of sublethal neonicotinoid exposure on black tiger shrimp (Penaeus monodon) and assess the implications for shrimp aquaculture and consumer safety. A series of well-replicated controlled experiments compared the effects of aqueous and dietary exposure on survivorship, growth, behaviour, and biochemical stress indicators. Neonicotinoid residues were extracted from tissue and water by QuEChERS and solid-phase extraction, respectively, then analysed by liquid chromatography-mass spectrometry. Sublethal impacts on flesh biomarkers examined AChE, CAT and GST enzyme activity, as well as lipid and protein profiles. Acute toxicity tests showed that clothianidin (190 μg L-1), thiamethoxam (390 μg L-1), and imidacloprid (408 μg L-1) were acutely toxic to juvenile P. monodon, while acetamiprid was non-toxic to shrimp up to 500 μg L-1. Thiamethoxam, clothianidin, and imidacloprid residues accumulated rapidly in shrimp from either dietary or aqueous exposure, with accumulated residues exceeding maximum residue thresholds for seafood. A four-day depuration reduced accumulated residues, although a more extended depuration period is necessary for clothianidin exposed shrimp. Positive correlations existed between neonicotinoid tissue concentration and biomarker activity for aqueous and dietary exposure routes. Elevated AChE impacted neurotransmission affecting movement, while elevated CAT and GST confirmed an oxidative stress response. Routine monitoring of AChE, CAT, and GST biomarkers could provide an early warning of shrimp stress, with an elevated response in all three biomarkers indicating that investigating potential contamination by neonicotinoid insecticides would be worthwhile. Neonicotinoids reduced feed consumption affecting shrimp nutritional status, altering fatty acid composition, carbohydrate metabolism, amino acid biosynthesis, and calcium signalling. Exposure increased mortality and inter-moult interval and reduced weight gain and growth rate, thus posing a risk to aquaculture productivity. A reduced abundance of eicosanoid precursors and pathogen detection proteins suggest pathogen defences may be compromised. Allergenic protein abundance increased and may affect food safety. Overall, this study confirmed that shrimp are vulnerable to neonicotinoids from aqueous or dietary sources and that exposure could significantly impact food safety and aquaculture productivity. The threat of increased neonicotinoid use and the increased risk to shrimp aquaculture requires effective monitoring and regulation in shrimp producing areas.

The impacts of sublethal neonicotinoid exposure on shrimp

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The impacts of sublethal neonicotinoid exposure on shrimp

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