Journal of comparative physiology. B, Biochemical, systemic, and environmental physiologyOct 13, 2023

Changes in gut melatonin with age and its possible role in feeding and digestion during carp growth from young to adult

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗

Updated Mar 29, 2026

Abstract

The highest gut melatonin titer was observed in fingerling carp (BW ≥ 3 g to ≤ 20 g).

Gut melatonin titer is highest in fingerlings and decreases in later growth stages, with the lowest levels in late juveniles.
A negative correlation exists between gut development and melatonin content.
Gut melatonin is positively associated with feeding intensity and gastro-somatic index (GaSI).
There is a negative relationship between gut melatonin and ovarian onset and development.
Evidence suggests that gut melatonin may play a significant role in regulating digestive physiology as carp mature.

Simplified

The present study aims to understand the feeding-related age-bound changes in gut histoarchitecture and its response to gut melatonin (GM) titer regulating major digestive enzymes in carp, Catla catla. Therefore, gut samples were collected from different growth stages of carp, viz. (i) fingerling (FL), body weight (BW) ≥ 3 g to ≤ 20 g; (ii) advanced fingerling (AFL), BW > 20 g to ≤ 40 g; (iii) early juvenile (EJv), BW > 40 g to ≤ 70 g; (iv) juvenile (Jv), BW > 70 g to ≤ 200 g; (v) late juvenile (LJv), BW > 200 g to ≤ 300 g; (vi) preadult (PA), BW > 300 g to ≤ 500 g; (vii) subadult (SA), BW > 500 g to ≤ 1.00 kg; and (viii) adult (AD), BW > 1 kg to ≤ 2.5 kg. Data analysis revealed that the highest titer of GM was noted in FL, moderate in AFL, Jv, and PA, lower in EJv, SA, and AD, and lowest in LJv. Results depicted a negative correlation between the development of the gut and its melatonin content. Moreover, GM was positively associated with feeding intensity and gastro-somatic index (GaSI) and negatively related to ovarian onset and development. Following correlation and principal component analysis, several pieces of evidence were recorded on the role of gut melatonin in regulating digestive physiology. Finally, it indicates that gut melatonin has a progressively influential role in improving digestion, particularly protein and microbial digestion, with the development of an adult gut from the fingerling stage.

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Changes in gut melatonin with age and its possible role in feeding and digestion during carp growth from young to adult

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