Endocrine regulation of feeding in non-transgenic and transgenic fluorescent orange tiger barb (Puntigrus tetrazona)

Tiger barbs are popular tropical aquarium fish but despite their economic importance, nothing is known about their feeding physiology, in particular their endocrine regulation of feeding. The tiger barb has also been used to make genetically modified fluorescent fish but the influence of this genetic modification on their physiology is poorly understood. In this study, we submitted both non-transgenic (NT) and transgenic fluorescent orange (T) fish to 2 weeks of fasting or different temperatures (20, 25 and 30 °C) and assessed food intake and the expression of appetite regulators in brain, intestine and liver. Fasting had no effect on appetite regulators in the intestine, and decreased liver leptin expression in NT fish only. Fasting caused an overall increase and decrease in brain orexigenic and anorexigenic factors, respectively. The nature of peptides affected by this response differed between strains (MCH, ghrelin, POMCb in both NT and T, orexin in NT only, CRF and CCK in T only). In both T and NT fish, increasing temperatures increased food intake. Temperature affected the expression of most of the peptides examined, but the effects differed between the two fish strains. A shift from 25 to 20 °C increased hepatic leptin in NT and T, and intestine ghrelin in NT and had no effect on brain expression. A shift from 25 to 30 °C did not affect intestine or liver expressions, increased orexin, MCH and CRF brain expression in NT and T, and increased POMCb and CCKa expressions in T. Our study presents new information on the endocrine regulation of feeding in tiger barb, and provides insights on how transgenesis might affect feeding physiology of fish.