Imidacloprid (IMI), a widely used neonicotinoid insecticide, has raised environmental concerns due to its potential impact on non-target aquatic organisms. This study investigates the effects of IMI exposure on the intestinal immune function of red swamp crayfish (Procambarus clarkii, P. clarkii), focusing on oxidative stress, inflammatory response, and autophagy. The P. clarkii was exposed to different doses of IMI (0, 10.93, 21.86, 43.73, 87.45 μg/L) for 96 h. Our findings reveal that IMI exposure leads to a survival rate of less than 70% when the concentration was 87.45 μg/L at 96 h. Hemolymph LZM and AKP contents were significantly decreased at the medium and high concentrations, and the expressions of hsp70 and nf-κb genes were significantly up-regulated. The expression of the lysozyme gene was significantly down-regulated. Additionally, the activities of SOD, CAT, and GPX were significantly decreased, the contents of MDA were significantly increased, and the gene expressions of CuZnsod, mMnsod, cat, and gpx in the gut were significantly down-regulated after exposure to medium-high IMI. The expression of autophagy-related genes showed that the expressions of beclin1, atg5, atg13, and lc3c genes in the medium- and high-concentration groups were significantly up-regulated. In summary, this study elucidates that medium-high levels of IMI exposure impair intestinal immune function in P. clarkii through mechanisms involving oxidative stress, inflammatory response, and autophagy.

In pursuit of sustainable aquaculture, this study was performed to evaluate chicken meal as a substitute for fishmeal in bullfrog diets. Three experimental groups were established: a control group (FM) with 20% fishmeal, a CM50 group with 50% replacement (10% fishmeal), and a CM100 group with 100% replacement (0 fishmeal). Bullfrogs were fed for 56 days. The CM50 group exhibited significant increases in total weight gain and survival rate and a notable decrease in feed coefficient (p < 0.05). However, the CM100 group showed contrary effects. Increasing chicken meal substitution correlated with decreased amino acid content in muscle. Notably, the CM50 group demonstrated enhanced activities of antioxidant enzymes (CAT, T-AOC) and elevated gene expression levels (cat, sod, gst, etc.) in muscle and the intestine (p < 0.05), improved intestinal morphology, enhanced digestive enzyme activities (amylase, lipase), and reduced expression of inflammatory factors (il-1β, il-8, il-17, etc.). Conversely, the CM100 group’s indicators regressed to levels similar to or worse than those of the FM group. Therefore, a 50% substitution of fishmeal with chicken meal effectively promoted bullfrog survival, protected the intestines, and enhanced antioxidant capacity, supporting its potential as a fishmeal alternative. However, the adverse outcomes of the CM100 strategy, including growth retardation and reduced amino acid content in muscle, indicate that complete replacement is unsuitable.

At present, studies on tadpole nutrition and metabolism are scarce. This study aimed at comparing the influence of two protein sources, fishmeal (FM) and dried whole egg powder (DWEP), on tadpoles from the perspective of growth, the metamorphosis rate, lipid metabolism, antioxidant properties and the intestinal flora. In this experiment, the control diet was set to contain no FM or DWEP. Based on the control diet, 5% and 10% FM or DWEP were included, respectively. The results of the experiment indicated that FM or DWEP inclusion significantly enhanced the growth performance and metamorphosis rate (p < 0.05); activated hepatic lipid metabolism, as manifested by enhanced LPL and HL activity; upregulated lipid metabolism-related gene expression (fasn, acc, acadl and cpt1α) (p < 0.05); and distinctly elevated the activity of SOD, CAT and GPX (p < 0.05), suggesting improved antioxidant capabilities (p < 0.05). Moreover, the inclusion of FM or DWEP elevated the relative abundance of Actinobacteria and Actinomyces and reduced the relative abundance of Proteobacteria. Unexpectedly, no significant differences were observed between the FM and DWEP groups regarding the above detected indices. This indicates that using DWEP to replace FM is a viable option.