Effect and associated mechanism of copper plates on Cryptocaryon irritans tomonts in large yellow croaker (Larimichthys crocea) farming

Cryptocaryonosis, caused by the ciliate parasite Cryptocaryon irritans , results in large economic losses in large yellow croaker (Larimichthys crocea) culture. In order to explore the effect of copper plates on C. irritans tomonts, incubation rate, morphological characteristics, copper concentration, and transcriptome changes were studied. After copper plate treatment for 6 h, the tomonts showed erosion in the internal structure and the tomonts wall exhibited reduced transparency. Compared with the control group, the hatching rate of tomonts in the treatment group was significantly lower. Copper concentrations of tomonts in the treatment group was 340.67 +/- 0.94 mg/kg, while the copper value in the control group was 22.40 +/- 0.91 mg/kg. Transcriptome analysis revealed that 21 GO terms were significantly enriched by differential expression genes (DEGs). Among them, the regulation of cellular respiration and protein-containing complexes were highly enriched (q-value < 0.001). The results of KEGG analysis showed that the ribosome pathway and the systemic lupus erythematosus pathway were the most significantly enriched pathways. In addition, most of the annotated DEGs on these two pathways were down-regulated indicating the killing effect was mainly mediated by ribosomal proteins, histones, and small nuclear ribonucleoproteins.