LED light spectra differently affected growth, antioxidant capacity, stress response, GH/IGF and HPI axis in largemouth bass (Micropterus salmoides) larvae

Abstract

This study aimed to investigate the effects of white (control), blue, green and red light-emitting diodes (LEDs) spectra on the growth, antioxidant and stress response, and mRNA levels in the growth hormone/insulin-like growth factor-I (GH/IGF) axis, NF-E2-related factor 2 (Nrf2) pathway and hypothalamus–pituitary–interrenal (HPI) axis in largemouth bass (Micropterus salmoides) larvae. The blue and green LEDs significantly increased body weight and condition factor, which may be explained by increased mRNA expression of GH/IGF axis genes that encode insulin-like growth factor, growth hormone, hormone release hormone, and growth hormone receptors. The promoted antioxidant capacity was observed in the brain of fish subjected to blue LEDs and liver of fish subjected to blue and green LEDs, which may be associated with increased expression of nrf2 and its downstream genes. Both blue and green LEDs did not significantly affect cortisol levels but down-regulated several HPI axis genes. Unlike blue and green LEDs, red LED increased malondialdehyde (MDA) levels, reduced the activities of superoxide dismutase (SOD) and catalase (CAT), and total antioxidant capacity (TAC), and down-regulated Nrf2 signaling in the head kidney. Cortisol levels increased, and HPI axis was down-regulated in fish exposed to red LEDs. Taken together, blue and green LEDs had beneficial effects on growth, antioxidant capacity, and stress response via physiological and transcriptional regulation of GH/IGF axis, Nrf2 and HPI axis signaling, which may help to improve the welfare of largemouth bass in indoor recirculating water aquaculture facilities.