An 8-week feeding trial was conducted to investigate the effects of different dietary selenium yeast levels on growth, nutrient retention, waste output, and antioxidant capacity of juvenile triangular bream (Megalobrama terminalis). Five isonitrogenous (320 g/kg crude protein) and isolipidic (65 g/kg crude lipid) diets were formulated, with supplementation of graded levels of selenium yeast at 0 (diet Se0), 1 (diet Se1), 3 (diet Se3), 9 (diet Se9), and 12 g/kg (diet Se12). No significant differences were found in initial body weight, condition factor, visceral somatic index, hepatosomatic index, and whole body contents of crude protein, ash, and phosphorus among fish fed different test diet. The highest final body weight and weight gain rate were found in fish fed diet Se3. The specific growth rate (SGR) is closely related to dietary selenium (Se) concentrations with a relationship described as SGR = – 0.0043   S e 2 + 0.1062   Se + 2.661 . Higher feed conversion ratio was found, while lower retention efficiencies of nitrogen and phosphorus were found in fish fed diets Se1, Se3, and Se9 than in fish fed diet Se12. Contents of selenium in whole body, vertebra, and dorsal muscle increased with dietary supplementation of selenium yeast increased from 1 mg/kg to 9 mg/kg. Lower nitrogen and phosphorous waste was found in fish fed diets Se0, Se1, Se3, and Se9 than in fish fed diet Se12. Fish fed diet Se3 exhibited the highest activities of superoxide dismutase, glutathione peroxidase, and lysozyme while the lowest malonaldehyde content in both the liver and kidney. Our results showed that the optimal dietary selenium requirement for triangular bream should be 12.34 mg/kg based on the nonlinear regression on SGR, and fish fed diet Se3 in which selenium concentration (8.24 mg/kg) was close to the optimal requirement displayed the best growth performance, feed nutrient utilization, and antioxidant capacity.

Temperature is one of the major factors controlling the growth and development of Pyropia. Here, we set out to discover the most important changes arising at the growth rate, ultrastructure, lipids and low‐molecular‐weight carbohydrates of Neoporphyra haitanensis conchocelis under low temperature (12°C), mid‐temperature (23°C) and high temperature (28°C). Results showed that lower growth rate was at 12°C, while the conchosporangia formed under 28°C. Thicker cell wall was under 28°C. Larger size of plastoglobuli exhibited under 12°C. Less total contents of monogalactosyldiacylglycerols, digalactosyldiacylglycerols, sulfoquinovosyldiacylglycerols and phosphatidylinositols were under 12°C, while more total contents of phosphatidylcholines, phosphatidylethanolamines, phosphatidylglycerols and triglycerides were under 12°C. The ratio of unsaturated to saturated fatty acids in phosphatidylcholines, phosphatidylethanolamines, phosphatidylglycerols, monogalactosyldiacylglycerols, digalactosyldiacylglycerols, and sulfoquinovosyldiacylglycerols increased at 12°C and decreased at 28°C. The contents of floridoside and isofloridoside were more under 12 and 28°C than that under 23°C. Taken together, these findings indicated that temperature affected the physiological properties of Neoporphyra haitanensis.