Abstract
UVA is the most common type of solar UV radiation in aquatic environments; however, the effects it causes in shrimp farming in recirculating water systems (RAS) is unclear. Thus, the growth performance, immune responses, antioxidant status and apoptosis-related gene expression in Pacific white shrimp, Penaeus vannamei (body weight 9.56 ± 0.10 g), reared with 12L: 12D full spectrum light as background light under five UVA (peak at 400 nm) photoperiods (0L: 24D, 2L: 22D, 4L: 20D, 8L: 16D and 12L: 12D) at a light intensity of 1 W/m2 were investigated. The results showed that the 2L: 22D and 4L: 20D UVA photoperiods enhanced the growth performance and reduced the feed conversion ratio and the shrimp mortality. Shrimp exposed to UVA (2L: 22D and 4L: 20D) also displayed higher levels of hepatopancreas catalase (CAT), superoxide dismutase (SOD), acid phosphatase (ACP), phenol oxidase (PO) and lysozyme (LZM) compared to the 8L: 16D and 12L: 12D groups. The malondialdehyde (MDA) levels increased in line with the extension of the UVA irradiation time. The mRNA expression of apoptosis-related genes in all the UVA treatments were significantly higher than with the control treatment, except for the 2L: 22D group. The results of the 2L: 22D and 4L: 20D treatments were significantly higher than those of the control group, except for LGBP. In conclusion, 2L: 22D and 4L: 20D UVA photoperiods increased growth performance and decreased FCR, improved the innate immunity and antioxidant response and reduced the mortality rate in adult shrimp.
Highlights
Ultraviolet light is a crucial element on the natural spectrum and serves a variety of ecological purposes
The results showed that the growth rate and SGR of 2L:22D and 4L:20D groups were significantly higher than in the control group (p < 0.05), whereas there were no significant differences between the above two groups
UV-induced genetic changes have been found in studies to have a deleterious impact on ontogenetic development [18], as when compared to individuals exposed to natural sun conditions, Vitt et al [19] discovered that exposing stickleback Gasterosteus aculeatus to UVB radiation for an extra 4 h each day resulted in decreased growth and loss of body condition
Summary
Ultraviolet light is a crucial element on the natural spectrum and serves a variety of ecological purposes. UVC is extremely detrimental to organisms, the most harmful wavelengths are usually absorbed by the stratospheric ozone and, never reach the Earth’s surface [1,2]. Due to climate challenges such as global warming and ozone layer depletion, the amount of ambient UV radiation reaching the Earth’s surface has grown, which has ramifications for ecosystems. The impact of organisms’ exposure to ambient UV light is frequently studied, such as the evaluation of the UVA Photoperiod. Browman et al [4] reported that UVA and polarized light purportedly increase the visibility of prey by enhancing target contrast for fishes that can perceive them. Alves et al [5] described the harmful effects of UVA and UVB radiations in fish at different lifecycle stages, including embryo, larvae, juveniles and adults. According to previous research in our laboratory, the full spectrum plus a UVA light environment was most conducive to the development of P. vannamei [10]
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