Age-related changes in the gut melatonin levels and its possible role in the regulation of feeding and digestibility, with the development of the gut from fingerling to adult stages of carp, Catla catla

Impacts of Protein-, L-Tryptophan-, Carbohydrate-, Oil-Rich Diets on Growth Performance, Levels of Melatonin, Oxidative Stress, Antioxidative Agents, and Vital Digestive Enzymes in the Gut of Juvenile Carp (<I>Catla catla</I>)

“…In the present study, we worked on the early stage of juveniles, which exhibits a particular type of feeding preference and subsequent enzymatic actions. As noted in a recent publication 20 by our group, the higher α-amylase activity was recorded in the early stage (Fingerling), protease in the middle (Juvenile), and lipase and cellulase in later (Adult) stages of the growth phase. This indicates that similar kinds of food for all stages of carp is not suitable; instead, it is essential to understand the best food quality appropriate for a particular age group.…”

“…Melatonin concentration was quantified from the gut tissue extracts using the commercially available ELISA kit (Melatonin ELISA, IBL, Germany), following the manufacturer's instructions 20,52,53 . The absorbance was taken at 405 nm in a Bio-Rad iMark Micro Plate Absorbance Reader.…”

“…However, the availability, timing, and frequency of feed(s) per day 4,5,9,[12][13][14][15][16] , and even the quality of food supplied 7,17,18 might influence the melatonin content within the gut, at least in fish species 1,19 . A recent study has demonstrated that gut melatonin levels may also vary with the different growth stages of carp, as varied feeding intensities were recorded in their different developmental stages 20 . In the current decade, research in gut melatonin is gaining attention because, in addition to its endocrine functions, the molecule is playing a significant role as an autocrine, or paracrine, or luminal effector, or detoxifying modulator 19 in the context of regular activities of digestion of food particles for its better nutritional assimilation by the animal.…”

“…However, the present study sounds unique when the role of gut melatonin in oxidative stress management and digestive functions comes under the context of seven different quality dietary groups. Different dietary criteria have been provided by altering the nutrient matters of the experimental diets to the juveniles of the fastestgrowing Indian major carp (IMC), Catla catla, which achieves reproduction capability in just two years 20 . Moreover, being a tropical surface-dwelling carp, it also retains tremendous potential to act as the model organism for melatonin-related studies 8,9 .…”