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Digestive rhythms in fish larvae and juveniles. From molecular gene expression to enzymatic activity

AuthorsYúfera, Manuel ; Navarro, Gabriel ; Mata, J. A. ; Moyano, Francisco Javier; Martínez-Rodríguez, Gonzalo
Issue DateMay-2015
CitationWorld Aquaculture (2015)
AbstractThe aim of this review is to remark the importance of having circadian and postprandial records of the digestive function in fish. Most teleostean fish are visual feeders and exhibit rhythmic daily feeding patterns accordingly to photoperiod and food availability. In farmed fish, two different feeding situations can be found in larval and juvenile stages respectively. During the larval stage, live prey is frequently supplied along the day to maintain a permanent availability in the water column, while in the juvenile stage, food is offered in one or several discrete meals. Although in a different way, in both cases daily feeding pattern will change with changes in the illumination period and meal timing. The daily and postprandial digestive patterns of the different digestive enzymes are directly depending on these changes in the feeding pattern. Unfortunately, information about digestive daily rhythm in different fish species both in larval and juvenile/adult stages is still very scarce and practically restricted to pancreatic and gastric enzymes. Therefore, a global picture of the digestive function is far to be achieved. Larval fish reared with permanent food availability and under light/dark photocycle exhibit clear circadian rhythms in trypsinogen gene expression and trypsin activity. While the trypsin activity peaks in concordance with the gut content, the trypsinogen expression is upregulated before the start of illumination and feeding period. Lipase and amylase activity follow different patterns and the activity may increase before and after the daily maximum of gut content. Nevertheless, although with some variations, the molecular expression exhibits the same anticipation behaviour observed in trypsinogen and tend to increase before the feeding period. Interestingly, these rhythms of activity and expression are maintained even under permanent illumination, although without synchrony with the subjective day/night period. Some species are not strict visual feeders and the feeding behaviour changes throughout the development. In this case, the digestive rhythms also accommodate to ingestion rhythms. On the other hand, in juvenile fish the digestive function is largely dependent on feeding protocol and it may change with meals time and frequency, but always trying to optimize the digestion efficiency. In addition to inter-specific temporal feeding behaviour, diurnal and nocturnal feeding groups have been described in some farmed species. This diversity of feeding protocols and behaviours together with the lack of studies makes very complicate to define general rules to optimize the digestion efficiency. Particularly remarkable are the restrictions found in the activation of pepsin activity due to changes in the gastric pH with meal time and frequency.The main point in describing the complete circadian patterns in the activity and expression of digestive enzymes is the evidence for misinterpretation when the measurements are restricted to only one daily point, because it can fall in any moment of the activity or expression cycle.
DescriptionTrabajo presentado en el World Aquaculture (Aquaculture For Healthy People, Planet and Profit), celebrado en Jeju (Corea del Sur) del 26 al 30 de mayo de 2015.
Appears in Collections:(ICMAN) Comunicaciones congresos
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