Abstract
Haliotis diversicolor aquatilis (H. diversicolor aquatilis) is one of the aquaculture abalone species in Jeju Island, South Korea. The high water temperature in the middle of the summer season frequently limits the aquaculture productivity of abalone. To cope with the problem, this study aimed to investigate viability, attachment rate, changes of immune response, and physiological properties of juvenile small abalone Haliotis diversicolor aquatilis against high water temperature stress under 60CO-gamma irradiation-mediated hormetic effects. To examine physiological changes of abalone, the gamma-ray irradiated and non-irradiated groups were distinguished by grouping a total of 70 abalones in a treated group and a control group (each group included twenty-five female and ten male abalones). The treated group was exposed to 60CO-gamma irradiation using a designed experimental apparatus, the control group was not. Our results revealed that the low level of gamma ray (20 Gy)-irradiated Haliotis diversicolor aquatilis showed a 100% survival rate during the experiment. After gamma ray exposure, all the abalones were cultured without feeding and bioactivities were measured to examine gamma ray-induced physiological responses. The results suggested the potential for selective breeding using gamma ray irradiation hormesis to manipulate the number of eggs, fertilization rate, hatching rate, and attachment rate. The shell length of juvenile abalone was significantly enhanced by a 20 Gy radiation dose. We could presume that the effect of hormesis in the gamma-ray irradiation parent shellfish also had a genetic effect on the offspring. In order to verify changes in immune response and stress tolerance of abalone under high temperature stress, lysozyme activity and survival rates were compared at a water temperature of 30 °C. Interestingly, the 60Co gamma ray-irradiated abalones exhibited almost a 1.65-fold enhanced survival rate along with reduced lysozyme activity after 12 h of high temperature stress. Our results speculate that low levels of 60Co gamma ray-mediated hormetic effects can be an effective strategy for shell length growth and high temperature stress tolerance.
Highlights
Hormesis can be explained as an adaptation to harsh changing environments
Hormesis and increased growth has been reported for the marine abalone species, Haliotis discus hannai and Haliotis discus at gamma-ray doses of 30 Gy and 20 Gy respectively [5,6], no studies have been undertaken for Haliotis diversicolor aquatilis
As a result of measuring the activity of lysozyme in Haliotis diversicolor aquatilis by the low salt stimulation, it was reported that the lysozyme activity was significantly increased and decreased in other experimental groups compared to the control group immediately after administering stress. These results suggest that the survival rate is improved by the increase in the initial immune-activity right after applying water temperature and salinity stress, and the abalones with strong resistance increase initial immune-activity, stabilize rapidly
Summary
Hormesis can be explained as an adaptation to harsh changing environments. The bioactive mechanism of hormesis has yet to be established. The low dose radiation produces proteins related to the DNA recovery process while the DNA synthesis process is temporarily inhibited, providing sufficient time for the treated cells to recover. Resistance is increased when free radicals spread [1]. Low-dose radiation treatment technology such as gamma radiation may be used to induce hormesis in plant species including cabbage, pepper, and gourd [2,3] to stimulate growth, increase viability and productivity, stabilize food supply, and increase plant resistance to environmental stressors [4]. Hormesis and increased growth has been reported for the marine abalone species, Haliotis discus hannai and Haliotis discus at gamma-ray doses of 30 Gy and 20 Gy respectively [5,6], no studies have been undertaken for Haliotis diversicolor aquatilis
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