Effect of light intensity on the growth and energy allocation of green and red variants of Apostichopus japonicas Selenka

We evaluated the effect of light intensity on the specific growth rate(SGR),food intake(FI),food conversion efficiency(FCE),and the energy budget of red and green variants of the sea cucumber Apostichopus japonicus.We reared 96 green(6.28 g ± 0.02 g) and 96 red(6.34 g ± 0.04 g) individuals under six light intensities(0,50,300,1 000,2 000,or 3 500 lx) for 60 d at 16°C.Light intensity had a significant effect on specific growth rate(SGR)(P0.05) in both variants.Within the range of 50–3 500 lx,there was a negative relationship between the SGR of sea cucumber and illumination intensity.Both red and green variants grew fastest(P0.05) at levels 50 lx.The maximum SGR,FI,and FCE(P0.05) were observed in individuals reared under 50 lx.Stronger light intensity inhibits FI and reduces the efficiency of food conversion.The lower FCE under stronger intensity lighting may be function of the oxygen consumption rate(OCR).Our results suggest that OCR is significantly affected by light intensity(P0.05).The minimum OCR was observed in animals reared under 50 lx,suggesting that little energy was expended on respiration,with most being invested in growth.Energy metabolism was significantly affected by light intensity(P0.05).At light levels under 50 lx,A.japonicus allocate 7% for growth and 90% for respiration and production of feces.As light intensity increases,the energy allocated to growth decreases and is instead diverted to respiration and production of feces.