The regulation of circadian gene expression remains largely unknown in farmed fish larvae. In this study, a high-density oligonucleotide microarray was used to examine the daily expression of 13,939 ...unique genes in whole gilthead sea bream (Sparus aurata) larvae with fast growth potentiality. Up to 2,229 genes were differentially expressed, and the first two components of Principal Component Analysis explained more than 81% of the total variance. Clustering analysis of differentially expressed genes identified 4 major clusters that were triggered sequentially, with a maximum expression at 0 h, 3 h, 9-15 h and 18-21 h zeitgeber time. Various core clock genes (per1, per2, per3, bmal1, cry1, cry2, clock) were identified in clusters 1-3, and their expression was significantly correlated with several genes in each cluster. Functional analysis revealed a daily consecutive activation of canonical pathways related to phototransduction, intermediary metabolism, development, chromatin remodeling, and cell cycle regulation. This daily transcriptome of whole larvae resembles a cell cycle (G1/S, G2/M, and M/G1 transitions) in synchronization with multicellular processes, such as neuromuscular development. This study supports that the actively feeding fish larval transcriptome is temporally organized in a 24-h cycle, likely for maximizing growth and development.
This study aimed to find a way for increasing the water content after rehydration of microdiet particles for fish larvae and to assess whether such increase contributes to a better disaggregation and ...digestion of particles within the gut of gilthead seabream larvae (4–15 days after hatching, dph). Four microdiets were prepared with increasing amounts of carboxymethylcellulose (CMC): 0, 20, 40 and 80 g kg−1. The inclusion of CMC resulted in an effective increase of the hydration capacity of particles. Water content after immersion ranged from 800 g kg−1 in the microdiet without CMC to 900 g kg−1 with 80 g kg−1 CMC. Larvae of different ages were fed during 10 h with these microdiets. The microparticles containing 80 g kg−1 CMC were more degraded in the gut of the younger larvae. No clear differences were observed from 10 dph onwards. Differences in enzymatic activities were not evident except for α‐amylase in 6 dph larvae. Gene expression of the enzyme precursors did not show any relation to the water content of microdiets. Overall, the results indicate that increasing the water content up to 900 g kg−1 may enhance the disintegration of food particles within the gut of younger larvae and to a lesser extent affect the response of digestive enzyme activities.
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