No abstract

We evaluated the effect of winter feeding frequencies (F1: one daily meal; F2: two daily meals; F3: four daily meals; F4: continuous diurnal feeding using a belt feeder) on the growth performance, biochemical blood parameters, oxidative stress, and appetite-related genes in Takifugu rubripes held at a constant temperature (18.0 ± 1.0°C) for 60 days. The results showed that the nal weight, weight gain rate, speci c growth rate, and survival of tiger puffer in the F3 group showed the best growth performance. The total cholesterol, triglyceride, and glucose levels were signi cantly higher with the increased feeding frequency.We also observed the antioxidant enzymes (superoxide dismutase, catalase, glutathione, and glutathione peroxidase) and the digestive enzyme activities (trypsin, amylase, and lipase) in tiger puffers cultured in the F1 group were signi cantly higher than those in the F3 and F4 groups. In addition, the tiger puffers in the F1 group exhibited the highest expression of orexin and the lowest contents of glucose, tachykinin, cholecystokinin, and leptin among all the groups. In contrast, the mRNA levels of tachykinin, cholecystokinin, and leptin in the tiger puffers in the F4 group may be attributed to the negative feedback mechanism in the brain-hypothalamus-neuropeptide axis. All parameters exhibited relatively optimal levels in the F3 group. In conclusion, inappropriate feeding frequencies could have negative effects on growth and physiological indicators. The optimal feeding frequency for enhanced growth performance while maintaining a relatively good physical condition in juveniles of this species was four times a day.

Manganese is an indispensable trace element, however, it may be present at high concentrations in water and sediments of aquatic ecosystems due to natural and anthropogenic activities, and can interfere with physiological and biochemical mechanisms in fish. This study was conducted to determine the toxic effects associated with exposure to Mn2+ (0, 0.5, 1, 2, and 4 mg/L) for 30 d, regarding liver damage and apoptosis in Yunlong grouper (Epinephelus moara♀×E. lanceolatus♂). Expression of superoxide dismutase (sod) and catalase (cat) genes in the liver was significantly increased on days 10 and 20 following Mn2+ exposure (4 mg/L), but was reduced on day 30. Similarly, expression of glutathione peroxidase (gpx) and glutathione reductase (gr) genes was elevated after 10 d of exposure to 2 and 4 mg/L Mn2+, but decreased after 20 and 30 d. After 30 d of exposure to high concentrations (2 and 4 mg/L) of Mn2+, liver tissue showed hepatic sinusoidal gap congestion, dilatation, cell vacuolation, and necrosis. In addition, the activities of alanine aminotransferase (ALT) and aspartate transaminase (AST) as well as 8-hydroxydeoxyguanosine (8-OHdG) levels were significantly increased after Mn2+ exposure. Moreover, Mn2+ exposure altered the expression pattern of some pivotal genes associated to apoptosis (p53, bax, bcl-2, apaf-1, caspase-9, and caspase-3), which suggested that Mn2+ exposure induces apoptosis through the mitochondrial pathway. The above results showed that excessive Mn2+ induced apoptosis and liver damage in grouper through elicitation of oxidative stress. These insights help elucidate the mechanism by which Mn2+ induces toxicity in marine fish, and provide a new perspective regarding the detrimental effects of heavy metals in fish.

No abstract

We evaluated the effect of winter feeding frequencies (F1: one daily meal; F2: two daily meals; F3: four daily meals; F4: continuous diurnal feeding using a belt feeder) on the growth performance, biochemical blood parameters, oxidative stress, and appetite-related genes in Takifugu rubripes held at a constant temperature (18.0 ± 1.0°C) for 60 days. The results showed that the final weight, weight gain rate, specific growth rate, and survival of tiger puffer in the F3 group showed the best growth performance. The total cholesterol, triglyceride, and glucose levels were significantly higher with the increased feeding frequency. We also observed the antioxidant enzymes (superoxide dismutase, catalase, glutathione, and glutathione peroxidase) and the digestive enzyme activities (trypsin, amylase, and lipase) in tiger puffers cultured in the F1 group were significantly higher than those in the F3 and F4 groups. In addition, the tiger puffers in the F1 group exhibited the highest expression of orexin and the lowest contents of glucose, tachykinin, cholecystokinin, and leptin among all the groups. In contrast, the mRNA levels of tachykinin, cholecystokinin, and leptin in the tiger puffers in the F4 group may be attributed to the negative feedback mechanism in the brain-hypothalamus-neuropeptide axis. All parameters exhibited relatively optimal levels in the F3 group. In conclusion, inappropriate feeding frequencies could have negative effects on growth and physiological indicators. The optimal feeding frequency for enhanced growth performance while maintaining a relatively good physical condition in juveniles of this species was four times a day.