Behavioral characteristics and physiological ecological responses of Mizuhopecten yessoensis to predation by Neptunea arthritica cumingii
In this study, we investigated the effects of predation by the whelk Neptunea arthritica cumingii on the culture and survival of scallops (Mizuhopecten yessoensis) during bottom culture. The behavioral characteristics of three sizes (small, medium, and large) of scallops were assessed in response to exposure to N. cumingii. We also measured the activities of superoxide dismutase, catalase, arginine kinase, and octopine dehydrogenase in the gill, adductor muscle, and mantle tissues of scallops before and after exposure to predation. Tissues that exhibited significant differences between control and test specimens were selected for deep sequencing of the transcriptome to identify and validate the key genes that were sensitive to predation. We found that scallops escaped from N. cumingii predation by continuous shell closure or movement. The shell closure force increased with the scallop size, and scallops of the same size that were stimulated by the presence of N. cumingii closed their shells more frequently than control scallops. The shell closure ability of scallops of all sizes decreased as the duration of the experiment continued. The enzyme activities in the three scallop tissues changed significantly after continuous stimulation, and the trend was particularly obvious for the enzyme activities in the adductor muscles of medium-sized scallops. Transcriptome analysis of the adductor muscles from medium-sized scallops detected 405 differentially expressed genes (172 upregulated and 233 downregulated), where the expression levels of RYK, APC, BAMBI, WNT16, CACYBP, and RUVBL1 changed after stimulation by N. cumingii. The sequencing results were verified by quantitative real-time PCR. We hypothesize that these genes may be related to muscle movement and regulation in M. yessoensis after stimulation. In conclusion, when M. yessoensis was stimulated by the presence of predators, its behavioral characteristics and related physiological and ecological indexes changed significantly. These results were useful for developing specifications for M. yessoensis seedling casting during bottom culture.