Feeding rhythm of the zoea larvae of Scylla paramamosain: The dynamic feeding rhythm is not completely synchronized with photoperiod

Abstract

The feeding rhythm is one of the key factors determining the success of artificial breeding of S. paramamosain. To understand the feeding rhythm of the different zoea larva developmental stages of S. paramamosain, the feeding rate, digestive enzyme activity, and expression of metabolism-related genes were investigated in the present study. The results showed that the S. paramamosain feeding rate has strong diurnal feeding rhythm, being significantly higher at 10:00–14:00 from stages ZI to ZIV. While the feeding rate peaked at 14:00 on Days 10 and 11, the peak shifted to 18:00 on Day 12. The activity of digestive enzymes amylase, pepsin and lipase decreased at night but increased in the daytime, showing a single-phase rhythm similar to that of the feeding rate, suggesting that the digestive enzyme activity was closely associated with the feeding rate during the larval development. Compared to pepsin and lipase, the activity of amylase was the most consistent with feeding rate. In particular, amylase activity peaked at 18:00 on Day 12. Due to its synchronicity with feeding activity, the activity of amylase could provide a potential reference for determining the best feeding time during zoea stages in S. paramamosain breeding. Moreover, the relative mRNA expression of metabolism-related genes SpCHH and SpFAS at most tested points was lower from 10:00 to 14:00, but higher at 18:00 to 6:00 of the next day. On the other hand, the expression patterns of SpHSL and SpTryp were converse to those of SpCHH and SpFAS. Our findings revealed that the S. paramamosain zoea has an obvious feeding rhythm, and the most suitable feeding time was 10:00–18:00 depending on different stages. The feeding rhythm is a critical aspect in aquaculture, influencing a series of physiological functions in aquatic animals. This study provides insights into the feeding rhythm during the zoea development of S. paramamosain, making a significant contribution to optimizing feeding strategy, improving aquafeed utilization, and reducing the impact of residual feed on water environment.