Morphophysiological differences in the gastrointestinal tract of Mugil liza mullets from rearing and the environment
The mullet has a sophisticated gastrointestinal tract, allowing you to enjoy nutritionally poor food. Because the treatment is modulated by the different types of food available in the environment, the objective of the present study was to evaluate the morphophysiological changes in the digestive tract of mullets, Mugil liza, from different environments. Twenty specimens of M. liza were used, five from Praia do Cassino (PC), 10 from Lagoa dos Patos (LP). Of these, five were maintained for 147 days in a recirculation system (LP-RAS) and five in a network tank for x days (RAS-TR). LP-RAS organisms were fed twice a day with commercial feed with 38% CP and RAS-TR with 42% CP. All mullets were euthanized with benzocaine (500 mg / L) and immediately after CP organisms,LP and RAS-TR were transported to the laboratory in styrofoam with water + ice (temperature <4ºC). Weight, total length, intestinal quotient (IQ), stomach index (IE), stomach content index (ICE), pH of the tract and distribution of goblet cells in the caeca and intestine were analyzed. The specimens of the environment showed a statistically higher IQ, IE and ICE than that of captivity. The stomach pH of RAS-TR fish was more acidic than that of CP fish, and the LP and LP-RAS treatments remained in an intermediate condition. From the caeca there was no difference in pH between the different origins, except in the midgut. A greater number of goblet cells were found in the distal intestine and pyloric caeca, followed by the proximal intestine and the medium intestine.The data suggest that the morphophysiological changes are adaptations modulated by the degree of ease of digestion and absorption of the nutrients that each food contains due to its composition, so that the rations are assimilated faster, tend to reduce the weight of the stomach and the area absorption of the intestine. In addition, it is believed that the presence of more protein foods increases the release of gastric juice by reducing stomach pH. The largest number of goblet cells was found precisely in places where there is a need to increase absorption, lubrication and protection of the epithelium.