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Abstract: The major neutral lipase excreted by the pancreas in fish, is bile activated lipase (BAL). Here we present evidence that cod have a functional BAL and a non-functional pancreatic lipase related protein (PLRP). The Atlantic cod genome does not seem to contain colipase which is essential for pancreatic lipase activity. During the larval stages, the gene expression of BAL was low until the point when pyloric caeca started to differentiate and develop (~20mm standard length (SL)). Then the expression increased until ~50mm SL. The PLRP gene was expressed but showed very little regulation. The activity of neutral lipase did not increase in parallel to gene expression. The mismatch between activity and gene expression measurements may be partly explained by the unspecific analytical method, when analysing lipase activity in larva whole body. There is neutral lipase activity in numerous tissues in the fish larvae and the lipase activity in the gut, relatively to activity in the whole body, decreased with age. Furthermore, neutral lipase activity in rotifers was ten times higher than in whole cod larvae with full guts. Activity originating from the live prey may therefore explain the high whole body lipase activity from 3 to 20dph. The results also indicate that “adult type” digestion of neutral lipid develops late in the larval period (from 20mm SL), while other mechanisms of lipid uptake are active at the early larval stage. [ABSTRACT FROM AUTHOR]

Trypsin activity is usually measured using synthetic substrates, principally amide and ester derivatives of the amino acids lysine or arginine. The aim of this study was to compare trypsin activity measurements done with two assays using amide substrates and two assays using ester substrates. The activity of purified commercial enzyme extracts (bovine and Atlantic cod, Gadus morhua) were measured as was the activity in animal tissues (mice and Atlantic cod) at 5, 15, 25, and 35°C. The results clearly showed the potential impact of the substrate choice on the results when comparing different taxonomic groups at different temperatures. The sensitivity, the measurement reproducibility and even the thermal sensitivity of the enzyme varies according to the assay used. [ABSTRACT FROM AUTHOR]

The observations that the gastric evacuation of a meal was accelerated after ingestion of an additional meal, whereas the evacuation of the latter meal was slowed down were compared to the predictions of mass-dependent models derived from experiments on evacuation of single meals. In contrast, the present study on cod Gadus morhua fed identical double meals of sandeel Ammodytes tobianus demonstrated that the evacuation of each meal was slowed down relative to the evacuation of a single meal. This fact could be explained by the exposed meal surface area being reduced while the meals were together in the stomach as it was expected by a surface-dependent cylinder interpretation of the square-root model. The cylinder model forecasted accurately the observed evacuation of each meal in the double-meal situation. The simple surface considerations of the model further explained the discrepancies between observed and expected evacuation rates using mass-dependent models, which suggested that the above finding of the previous studies was an artefact. The ability of the cylinder model to predict properly also the evacuation of multiple meals in juvenile coho salmon Oncorhynchus kisutch indicated that the model would apply to gastric evacuation in small-sized predatory fishes as well. This should increase considerably its value as a generic tool for studies on the feeding biology of fishes in the wild. [ABSTRACT FROM AUTHOR]