Artificial light including blue-green wavelengths promotes growth of Rachycentron canadum with mRNA upregulation of appetite, growth and lipid synthesis

IntroductionCues from light, including photoperiod, intensity, and wavelength, can all impact physiology in fish. This study investigated the effect of light wavelengths on growth performance in the cobia Rachycentron canadum, a commercially valuable species in tropical waters.MethodsJuveniles were exposed to blue (BL, 466 nm peak), green (GL, 518 nm peak), or natural light (NL) for four weeks.ResultsCompared to NL, BL and GL significantly enhanced body weight (BW) by 27.6% and 23.2%, respectively, and increased specific growth rate (SGR) by approximately 24% and 23%, respectively. Transcript levels of key visual opsins were more highly upregulated by blue and green light in the diencephalon, compared to the retina, highlighting the importance of extraretinal photoreception in growth regulation. Comparison of transcript levels of various genes regulating appetite or lipogenesis showed a wavelength-dependent effect on growth stimulation in juvenile cobia. Green light influenced transcript levels of the appetite-stimulating peptide, neuropeptide Y (npy), in the brain, and growth hormone receptor (ghr) in the liver. Whereas blue light increased the transcript levels of an anorexigenic peptide, pro-opiomelanocortin (pomc), in the brain, and fatty acid synthase (fas) in the liver.DiscussionThese results align with adaptation to blue-green-dominated marine environment, emphasizing the valuable, non-invasive tool that spectral optimization can be in aquaculture.