中华绒螯蟹的摄食节律

为了探究中华绒螯蟹(Eriocheir sinensis)最适宜的投喂时间,本实验将120只初重约68 g的幼蟹随机分养在24个塑料缸(70 cm×40 cm×50 cm)中。采用一次饱食投喂(将昼夜分为8个时间点:10:00、13:00、16:00、19:00、22:00、01:00、04:00、07:00,每个时间段作为1个处理组,每天每个处理组饱食投喂1次)的方法研究中华绒螯蟹的昼夜摄食节律。结果显示,幼蟹在不同投喂时间点表现出24 h周期性的摄食节律,且总摄食高峰期在22:00。从其中6d的平均摄食量可以看出,河蟹主要在19:00~22:00时间段摄食;在肝胰腺酶活性方面,淀粉酶活性在19:00~22:00内高于其他各组,且在22:00获得最高值;脂肪酶、碱性磷酸酶和钠钾ATP酶酶活性有相似的变化趋势,在13:00~22:00时间段这些酶的酶活呈现上升的趋势,且最高值均在22:00获得。在相关摄食基因表达方面,肝胰腺中Leptin基因的相对表达量在22:00点显著低于13:00和16:00,与其他各组相比差异不显著(P0.05);肠道中胆囊收缩素(CCK)基因的相对表达量在22:00点显示出最低值,与10:00、13:00、04:00和07:00点相比差异显著(P0.05)。综上所述,中华绒螯蟹存在明显的摄食节律,这可能与光照紧密相关,最适宜的投喂时间为22:00。

Feeding rhythm of the Chinese mitten crab (Eriocheir sinensis)

The Chinese mitten crab (Eriocheir sinensis) is a native and important cultured freshwater that is widely distributed in the Yangtze Estuary, China. Many scholars have focused on crab farming, disease prevention, and diet. However, little is known about the feeding rhythm of Chinese mitten crabs, in regards to feeding mode, which is directly related to the feeding time, feeding method, and frequency of feeding strategies, which may affect feed efficiency, as well as aquaculture water. Accordingly, the present study investigated crab feeding behavior under a 24-h photoperiod and, ultimately, established a theoretical basis for determining optimal feeding time, which could benefit large-scale aquaculture and, therefore, improve feed utilization and reduce both water pollution and breeding costs. Crabs with weight of (68.0 ±2.4) g were randomly distributed among 24 cement pools (0.7 m×0.4 m×0.5 m, L×W×H). Each group had three cement pools replicates, each housing 5 crabs, and fed at different time points (10:00, 13:00, 16:00, 19:00, 22:00, 01:00, 04:00, and 07:00). After 10 d, three crabs from each pool were randomly selected and sampled for intestinal and hepatopancreas. The results showed that juvenile crabs exhibited different feeding patterns at different feeding times, and the peak of feeding was observed at 22:00. Based on the average food intake over 6 d, it was clear that the crabs fed primarily at 19:00-22:00. Meanwhile, amylase activity was higher in the hepatopancreas samples of crabs fed at 22:00 than in those of crabs fed at other times (except 19:00). Lipase, alkaline phosphatase, and Na⁺-K⁺-ATPase activities increased from 13:00 to 22:00 and decreased thereafter. Leptin expression in the hepatopancreas of crabs fed at 22:00 p.m. was significantly lower than that of crabs fed at either 13:00 or 16:00, whereas cholecystokinin (CCK) expression was lowest in the intestines of crabs fed at 22:00. In conclusion, feeding of Chinese mitten crab was with an increasing feed intake at 16:00; there after tend to decrease at 22:00. This could be attributed to the visual underdevelopment of the crabs. According to the observed feeding rhythm, Chinese mitten crabs are nocturnal and feed at night. The activities of digestion and absorption enzymes were lowest in crabs fed at 10:00-13:00 and increased from 16:00 to 22:00, with the highest level attained at 22:00. These results could indicate a strong the ability of nutrients digestion and absorption at 22:00. It was consistent with the trend of total feed intake. Digestive and absorption capacity are important indicators of feed utilization and animal growth, and enzyme activity can be used as an indicator of digestive and absorption capacity. On the contrary, the expression of leptin and CCK were downregulated at 22:00. These results were supported by the fact that leptin and CCK are involved in the regulation of food intake. According to previous studies, decreases in leptin and CCK increase the feed intake of animals, which also explains the why, in the present study, the highest feed intake was observed at 22:00. Overall, feeding Chinese mitten crabs at 22:00 could enhance digestion and absorption. Therefore, feeding at 19:00-22:00 could improve feed intake and efficiency.