Effects of different LED spectra on growth and expression of GH/IGF-I axis and apoptosis related genes in juvenile Takifugu rubripes
Authors: Liu Songtao , Fang Yingying , Liu Ying , Li Xin , Sun Fei , Wu Yanling , Ma Zhen , Ma He 
Published: October 2022

Light has long been known to have a profound influence on the growth and development of fish. The previous studies showed that different spectra had different effects on the growth of juvenile Takifugu rubripes. Among them, green light can promote the growth of Takifugu rubripes, but the influence mechanism is unknown. In this study, how different LED spectrums affect fish growth from the perspective of GH/IGF-I axis-related genes and apoptosis genes were deeply explored. In the experiment, juvenile Takifugu rubripes with an initial body length of (9.01 ± 0.70) cm and an initial body weight of (18.05 ± 3.17) g were selected as the research objects. 525 Takifugu rubripes juveniles were selected, cultured and monitored in five different LED spectrum treatment groups: white light (WL, λ 400-780nm), red light (RL, λ 625-630nm), yellow light (YL, λ 590-595nm), green light (GL, λ 525-530nm) and blue light (BL, λ 450-455nm). The photoperiod was 12L:12D, and the light intensity was set to 250 mW/m2. The effects of light spectrum on growth, melatonin synthesis, GH/IGF-I axis and relative expressions of apoptosis-related genes in juvenile Takifugu rubripes were studied, including arylalkylamine N-acetyltransferase (AANAT2), growth hormone (GH), growth hormone receptor type 1 (GHR1), growth hormone releasing hormone (GHRH), insulin-like growth factor type I (IGF-I), insulin-like growth factor type II (IGF-II), insulin-like growth factor binding protein (IGFBP), Bcl-2 protein family (Bcl-2), tumor suppressor (p53) and cysteine protease family (caspase 3, caspase 8, caspase 10) genes. The results showed that the final weight was the highest in the GL group (29.36 ± 3.78 g) and the lowest in the YL group (21.28 ± 2.56 g). The GL indeed promote the growth of Takifugu rubripes. The GHR1, IGF-I, IGF-II and IGFBP of juvenile Takifugu rubripes cultured under GL were significantly higher than those of WL (control group), BL and YL groups. The relative expression levels of GH and GHRH genes had no difference from those in the WL control group, and the relative expression levels of apoptosis genes in the GL group were significantly lower than those in the BL and YL groups. Under RL, the relative expression levels of all growth genes on the GH/IGF-I growth axis were relatively high. But at the same time, the relative expression of caspase 10 gene in juvenile Takifugu rubripes was high, and the growth state was inhibited. It is speculated that RL might disturb the endocrine system of the juvenile Takifugu rubripes, thus impeded its growth and development. Therefore, different LED spectra can affect the growth of juvenile Takifugu rubripes by affecting the expressions of GH/IGF-I growth axis and apoptosis-related genes: GL significantly promotes the growth of Takifugu rubripes, which may be due to that GL promoted the expressions of growth factors genes such as GHR1, IGF-I, and IGF-II, and decreased the expression of apoptosis-related genes, while the situation in the YL, BL and WL groups was on the contrary. RL significantly inhibited the growth of juvenile Takifugu Rubripes, which may be due to the fact that juvenile Takifugu Rubripes under RL were in a stressful state and the high expression of growth axis-related genes was not sufficient to offset the negative effects of the stress response, resulting in the inhibition of growth performance.