Effects of two juvenile hormone analogue insecticides, fenoxycarb and methoprene, on Neocaridina davidi.

Juvenile hormone analogue (JHA) insecticides are endocrine disrupters that interfere with hormonal action in insects by mimicking their juvenile hormones (JH). As the structure and functions of methyl farnesoate in crustaceans are similar to those of JH in insects, exogenous JHA insecticides could have adverse effects on the development and reproduction of crustaceans. This study examined the toxic effects of two JHA insecticides, fenoxycarb and methoprene, on a freshwater shrimp model of cherry shrimp, Neocaridina davidi. Both insecticides had detrimental effects on cherry shrimp, but fenoxycarb was more toxic than methoprene. Chronic exposure to these insecticides reduced the shrimp's body length and molting frequency. Based on transcriptome annotations for N. davidi, we identified important gene homologues that were active in both insect JH biosynthetic and degradative pathways as well as JH and ecdysteroid signaling pathways. Chronic treatments with JHAs had significant effects on these genes in N. davidi. Our transcriptomic analysis showed that genes involved in the pathways related to cuticle development, serine protease activity, and carbohydrate, peptide and lipid metabolic processes were differentially expressed in shrimp exposed to JHAs. These results demonstrate the toxicity of fenoxycarb and methoprene to freshwater crustaceans and indicate the need to monitor the use of JHA insecticides.
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