Effects of eyestalk ablation on growth, feeding behavior, movement and circadian gene expression in Haliotis discus hannai

The present study aimed to investigate the effects of eyestalk ablation on growth, feeding behavior, circadian movement activity, and circadian gene expression in the abalone Haliotis discus hannai. Abalones were divided into two groups: eyestalk-ablated (EA) and control (C), and were cultured for 60 days. Results showed that the EA group exhibited significantly higher growth rates in body weight compared to the C group. However, the EA group also had a higher mortality rate, indicating the negative consequences of eyestalk ablation. The feeding rate was significantly higher in the EA group, especially during nocturnal feeding, suggesting that eyestalk ablation may specifically affect nocturnal feeding behavior in abalone. Both EA and C groups displayed rhythmic oscillations in movement activity, with no significant differences in mesor and amplitude. Nevertheless, the peak of populational movement proportion in the EA group occurred approximately 2 h earlier than that in the C group. Transcriptome analysis identified 417 circadian genes, with the most significant enrichment found in the growth-related thyroid hormone signaling pathway. The expression of five core clock genes (clock, cry, rho, tipin, per) exhibited significant circadian rhythms in H. discus hannai, while their rhythmic oscillation significance was weaker in the EA group, except for the tipin transcript. These findings reveal that eyestalk ablation affects growth, feeding and locomotor behavior, and clock gene expression in abalone, providing valuable insights for understanding the circadian regulatory mechanisms and physiological ecological adaptations of abalone. However, due to its harmful effects on animal welfare and the limited promotion of growth, this technology is not advocated for use in aquaculture practices.