Digestive flexibility during fasting in fish: a review

Area of Science:

• Comparative physiology
• Animal biology
• Digestive system research

Background:

• Digestive flexibility is crucial for animals to optimize nutrient absorption and minimize energy expenditure.
• Vertebrates exhibit distinct digestive flexibility patterns based on metabolic costs and gut emptiness during fasting.
• Fish represent a unique group for studying digestive flexibility due to their diverse environments and feeding strategies.

Purpose of the Study:

• To analyze digestive tract down-regulation during fasting in fish.
• To evaluate how digestive flexibility in fish compares to that in other vertebrate groups (mammals, birds, amphibians, reptiles).

Main Methods:

• Review of existing scientific literature on fish digestive physiology during fasting.
• Comparative analysis of gut size changes, histological alterations, and enterocyte turnover rates.

Main Results:

• Gut size decay in fish during prolonged fasting is nearly linear, resembling patterns seen in some mammals.
• Histological changes in the fish gut during fasting are more comparable to those in amphibians and reptiles.
• Enterocyte turnover rates in fish are relatively short, falling between those of mammals and birds.

Conclusions:

• Fish exhibit a mixed pattern of digestive flexibility, incorporating mechanisms seen in both mammals and ectothermic vertebrates.
• Both changes in gut epithelial configuration and enterocyte turnover rates likely contribute to digestive tract regulation in fish during fasting.