In aquatic arthropods, molting is a pivotal physiological process for normal development, but it may also expose them to higher risks from xenobiotics, because the organism may take up additional water during that time. This study aimed to assess the effects of molting on bioconcentration and survival after 96-h exposure to insecticide fipronil with or without oxygenase (CYP450s) inhibitor piperonyl butoxide (PBO) of two estuarine resident marine crustacean species: the sand shrimp Crangon uritai and the kuruma prawn Penaeus japonicus, with 96-h LC₅₀ value of fipronil = 2.0 µg/L and 0.2 µg/L, respectively. Two graded concentrations included group high (H) (equivalent to the 96-h LC₅₀ values) and low (L) (one-tenth of the H group concentration). Molting and survival were individually checked, and internal concentrations of fipronil and its metabolites (fipronil desulfinyl, fipronil sulfide, fipronil sulfone) were measured. The results showed that, only fipronil and fipronil sulfone were detected from organism, and that internal concentrations of these insecticides in molted specimens were higher than those of unmolted ones but comparable with those of dead ones. Accordingly, mortality was more frequent in molted specimens than those that were unmolted. Furthermore, involvement of oxygenase and higher lethal body burden threshold may confer higher tolerance to fipronil in sand shrimp than in the kuruma prawn. This study is the first to demonstrate that the body-residue-based approach is useful for deciphering the causal factors underlying fipronil toxicity, but highlights the need to consider physiological factors in arthropods, which influence and lie beyond body burden, molting and drug metabolism.

在水生节肢动物中，蜕皮是正常发育的关键生理过程，但它也可能使它们面临更高的外源性风险，因为在此期间生物体可能会吸收额外的水。本研究旨在评估两种河口常驻海洋甲壳类动物：沙虾Crangon uritai和 kuruma 在有或没有加氧酶 (CYP450s) 抑制剂胡椒基丁醚 (PBO) 的情况下，在 96 小时暴露于杀虫剂氟虫腈后蜕皮对生物浓缩和存活的影响对虾对虾，氟虫腈的 96 小时 LC ₅₀值分别为 2.0 µg/L 和 0.2 µg/L。两个分级浓度包括组高 (H)（相当于 96 小时 LC ₅₀值）和低（L）（H组浓度的十分之一）。单独检查蜕皮和存活，并测量氟虫腈及其代谢物（氟虫腈脱亚磺酰、氟虫腈硫化物、氟虫腈砜）的内部浓度。结果表明，从有机体中仅检出氟虫腈和氟虫腈砜，这些杀虫剂在蜕皮标本中的内部浓度高于未蜕皮标本，但与死标本相当。因此，蜕皮标本的死亡率高于未蜕皮标本。此外，加氧酶的参与和较高的致死体负荷阈值可能使沙虾对氟虫腈的耐受性高于库鲁马对虾。