This study compared these aspects in omnivorous, herbivorous, plankton-feeding, and carnivorous fish from the same environment, Dianchi Lake, in Yunnan, China.
The researchers stated that fish feeding habits directly reflect the digestive ability to different nutrient components.
The fishes’ ability to digest and utilize different nutrients in feed is affected by the structure of the digestive tract, the digestive enzymes secreted and the intestinal microbiota composition, abundance, and diversity.
Twelve intestine samples were collected from each of the four species of fish including the mandarin fish, a carnivorous fish; grass carp, an herbivorous fish; the Dianchi high-back crucian carp, an omnivorous fish; and the Kunming schizothoracin, a plankton feeder.
Three fish per species were carefully dissected, and their intestines and hepatopancreas were collected in Eppendorf tubes and immediately frozen in liquid nitrogen.
These samples were mixed with nine times phosphate buffer saline, homogenized for 15 seconds in an ice bath, and then centrifuged at 13,400 g at 4°C for 20 minutes. The resulting liquid supernatant was used for digestive enzyme analysis.
The carnivorous mandarin fish was found to have higher trypsin and pancrelipase activity than other species, followed by the herbivorous, plankton feeding, and omnivorous fishes respectively.
The mandarin fish was also found to have more complex intestine structures, which the researchers believe have adapted to its feeding habits.
It has many branches and complex structures to increase surface area for digestion of ingested nutrients and absorption of digested nutrients as an adaption to the short intestine of a carnivorous fish and instable nutrition.
The intestinal lipase activity observed in this study was higher in the herbivorous and omnivorous fish species than the plankton feeder and carnivorous fish species.
The different feeding habits also shape the gut microbiota in these fish species, adapting them for various functions.
The omnivorous fish had the highest gut bacteria diversity, while carnivorous fish had Acinetobacter species, and herbivorous fish had Bacteroides species as dominant gut flora.
These bacteria may assist in protein and cellulose digestion, said the researchers. They added that this knowledge was valuable for optimising feed and feeding practices for these fish species.
Overall, the researchers concluded that the insight gathered is valuable for optimising feed and enhancing nutrient absorption, ultimately promoting fish growth.
Source: Ecology and Evolution
A comparison of digestive strategies for fishes with different feeding habits: Digestive enzyme activities, intestinal morphology, and gut microbiota
Authors: Fang et al.
https://doi.org/10.1002/ece3.10499
