Yuan Wang’s research while affiliated with Ningbo University and other places

The aim of this study was to provide a reference value for the safe regulation and control of ammonia nitrogen in the aquaculture of Sepia pharaonis. The effects of acute and chronic toxicity of ammonia on the cuttlefish, S. pharaonis, were tested experimentally using juvenile S. pharaonis. The results showed that the half-lethal concentration (LC50 ) values of ammonia nitrogen in juvenile S. pharaonis with a body weight of 6.52 ± 0. 23 g at 24, 48, 72, and 96 h were 31.72, 25.77, 23.33, and 18.33 mg/L, respectively, and the corresponding un-ionized ammonia nitrogen (UIA-N) concentrations were 1.66, 1.35, 1.22, and 0.96 mg/L, respectively. Compared with the control, the survival rate, specific growth rate, and feed intake of juvenile S. pharaonis declined significantly, and the feed conversion ratio and hepatosomatic index increased significantly at 56 d after exposure to >1 mg/L ammonia nitrogen. Juvenile S. pharaonis should be maintained at a concentration of ammonia nitrogen of no more than 1 mg/L (UIA-N is 0.056 mg/L) in culture, and removing harmful nitrogenous wastes from the seawater is critical in maintaining cuttlefish culture.

This study was conducted to determine the effects of dietary lipids on the growth performance, muscle composition, and enzyme activities of the stomach, intestines, and liver of Sepia lycidas juveniles. Fish oil and soybean lecithin were selected as lipid sources to formulate six experimental diets containing lipid levels of 3.68, 4.15, 6.62, 8.09, 9.56, and 11.03%. The feed efficiency first declined and then rose, with the lowest value obtained in individuals fed the 8.09% lipid content diet; the protein efficiency ratio significantly decreased with an increased lipid level. The highest crude protein content and lowest crude lipid content were simultaneously obtained in individuals fed the 9.56% lipid content diet. The activities of pepsase, trypsin, and intestine lipase initially increased before decreasing. The highest activities of protease, trypsin, and lipase were obtained in individuals fed the 9.56% lipid content diet, while the highest activity of amylase was obtained in individuals fed the 6.62% lipid content diet. Hepatic glutamate pyruvate transaminase and glutamic oxaloacetic transaminase initially increased and then held steady, with the highest activities simultaneously obtained in individuals fed the 9.56% lipid diet. Our results suggest that dietary lipids at a level of 9.56% could be the optimal lipid requirement for S. lycidas to grow and maintain normal metabolism.

To investigate the ammonia detoxification pathways of the cuttlefish, Sepia pharaonis, the effects of environmental ammonia nitrogen exposure (control, 1, 3, and 6 mg/L) on nitrogen metabolism were quantified in the hemolymph, liver, and gills. The levels of glutamine synthetase, glutamate dehydrogenase, and arginase activities and ammonia, glutamine, and urea concentrations in the hemolymph, liver, and gills significantly increased upon exposure to 3 and 6 mg/L ammonia nitrogen and exhibited a dose-dependent relationship with the ammonia exposure concentration. These results suggest two main pathways of metabolic ammonia detoxification in S. pharaonis exposed to ammonia in this study: (1) conversion of ammonia to urea, which is stored temporarily or excreted, via the ornithine-urea cycle and (2) conversion of ammonia to glutamine, which can be stored in the body or used for other anabolic processes.

To investigate the effects of starvation and re-feeding on survival rate, behavior, growth and digestive enzyme activities of juvenile Sepia pharaonis, the manipulative laboratory experiments were conducted with 0-6 days of starvation and 15 days of re-feeding to reveal the mechanism of compensatory growth. The results showed that starvation exerted a significant negative effect on the survival rate, growth, hepatosomatic index and digestive enzyme activities (P<0.05). The survival rate and digestive enzyme activities declined during the whole starvation process. After 3 days, the survival rate began to decline significantly, the decrease rate of body mass increased obviously and juveniles experienced some abnormal behaviors, such as inkjet, fighting and so on. The effects of starvation on digestive enzyme activities of juveniles were significant, and the digestive enzyme activities declined and then rose during the whole starvation process. The lowest amylase activity occurred after 4 days of starvation (0.07±0.02 U·mg⁻¹·prot⁻¹). The lowest lipase activity occurred after 2 days of starvation (18.47±2.07 U·g⁻¹·prot⁻¹), and the highest after 6 days (57.60±3.98 U·g⁻¹·prot⁻¹). The lowest pepsin and trypsin activities occurred after 5 days (1.98±0.59 U·mg⁻¹·prot⁻¹) and 4 days (186.68±20.72 U·mg⁻¹·prot⁻¹) of starvation, respectively. The effects of re-feeding on survival rate, growth, hepatosomatic index and digestive enzyme activities of juveniles were significant. The survival rate, specific growth rate, hepatosomatic index and feeding rate were negatively correlated with hunger processing duration. The survival rate, specific growth rate and hepatosomatic index showed no significant difference between 1 day starvation group and 2 days starvation group (P>0.05). The survival rate, specific growth rate and hepatosomatic index of 3 days to 6 days starvation groups were significantly lower than the control group. The feeding rates of 1 day and 2 days starvation groups were obviously higher than that of the control group. The feeding rate of 6 days starvation group was significantly lower than that of the control group. The amylase and lipase activities were not significantly different among different starvation treatments, whereas the pepsin and trypsin activities were significantly different, with the highest value in the control group (pepsin 7.06±0.64 U·mg⁻¹·prot⁻¹, trypsin 914.67±26.54 U·mg⁻¹·prot⁻¹) and the lowest value in the group with 6 days of starvation (pepsin 3.21±0.57 U·mg⁻¹·prot⁻¹, trypsin 660.04±37.92 U·mg⁻¹·prot⁻¹). Six days of starvation would be the point of no-return for the juveniles, without any compensatory effect after starvation and re-feeding.

The aim of this experiment was to determine the optimal initial food for hatchling cuttlefish and to investigate the influence of dietary composition on the growth, survival, and nutritional composition of cultured juvenile cuttlefish, Sepia pharaonis. Six experimental food groups were designated: Artemia nauplii, Calanus sinicus, frozen Hyperacanthomysis brevirostris, Ampithoe valida, H. brevirostris, and subadult Artemia. The results showed that survival, growth body biochemical composition of juvenile cuttlefish were significantly affected by experimental diets (P < 0.05). The optimum initial food was H. brevirostris, yielding a growth rate as high as 6.39%/d and survival rate reaching 81%. Growth rate was significantly positively correlated with dietary protein, Lys, Met, Phe, Iie, Leu, Trp, Arg, Gly, Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA), and 16:0 (P < 0.05). Survival was significantly positively correlated with dietary protein, Lys, Met, Phe, Val, Thr, Iie, Leu, Trp, Arg, Gly, EPA, DHA, and 16:0 (P < 0.05). The dietary protein, lipid, Met, Val, Thr, Leu, 18:0, and EPA were prone to accumulation within the body of juvenile cuttlefish (P < 0.05). These results demonstrate that juvenile cuttlefish exhibited the best growth rates and survival when fed a diet that supplied high-protein, low-fat, and larger quantities of Lys, Met, Phe, Val, Thr, Iie, Leu, Trp, Arg, Gly, EPA, DHA, and 16:0.