New insights into feeding behavior and digestive physiology of the Chinese mitten crab (Eriocheir sinensis) zoea 5 (Z5) and megalopa (M)

Abstract

The metamorphosis from zoea 5 (Z5) to megalopa (M) stage represents a critical transit in the larval development of the Chinese mitten crab (Eriocheir sinensis). This study investigated the feeding behaviors and digestive physiology of Z5 and M stages through behavioral, morphological, and physiological analyses. The results of feeding behavior have showed: 1) M stage had significantly higher average swimming speed (3.42 ± 0.22 cm/s) than Z5 (1.22 ± 0.15 cm/s) at 07:00 am, 12:00 pm, and 17:00 pm (p < 0.05). 2) Only M stage preferred Artemia salina in mixed feed trials. 3) M exhibited a distinct feeding rhythm with intake at 07:00 am and 17:00 pm being 1.15 and 1.21 times higher than at 12:00 pm, respectively (p < 0.05). 4) M consumed approximately 1.8 times more food than Z5 (p < 0.05). The results of digestive physiology have showed: 1) Food accumulation in the hepatopancreas peaked at 60 min in Z5 and 120 min in M by situ observations of accumulation in the hepatopancreas after ingesting red algal powder, with faster food transit time in Z5 (25–50 min) compared to M (80–120 min) (p < 0.05). 2) Significant rhythmic changes in digestive enzyme activities (amylase, trypsin, lipase) and gene expression were observed during the Z5 and M stages, with peak levels at 07:00 am and 17:00 pm for most enzymes. These findings provide crucial theoretical insights for optimizing feeding strategies and enhancing the healthy cultivation of E.sinensis larvae, potentially leading to improved yield and economic value of megalopae in aquaculture.