Effects of fasting and refeeding on the metabolic functions of the turtle Kinosternon scorpioides (Linnaeus, 1766) raised in captivity

Abstract

The metabolic responses of adult and young freshwater Kinosternon scorpioides turtles raised in captivity were evaluated. Two experiments were performed: a) blood metabolite changes caused by food deprivation, and b) liver and muscle glycogen and total lipid differences after fasting and refeeding. Blood glucose concentration of young animals was susceptible to food deprivation. In both groups this metabolite decreased after 30 days of fasting. Feeding for 15 days did not recover blood glucose. Total seric proteins were not affected by food deprivation. Fasting decreased blood urea nitrogen and the highest difference was found around 30 days. Uric acid increased in young animals after 60 days of fasting. Triacylglicerol decreased after 15 days of fasting and refeeding for 15 days recovered the pre-fasting levels. Free fatty acid plasma tended to increase around 15 days of fasting. Liver glycogen decreased at day 15 of fasting, being stable thereafter while muscle glycogen decreased at a slower rate. Total liver lipid stabilized after 30 days and then decreased 70% after 60 days of fasting. Muscle lipids remained stable throughout fasting. It could be concluded that fasting of Kinosternon scorpioides led to metabolic adaptations similar to the one reported from reptiles and fish.

The physiology of lipid storage and use in reptiles

“…() found that levels of plasma triglycerides were higher in recently fed green turtles compared to fasted individuals, and plasma triglycerides increased following refeeding. Similarly, fasting caused a drop in plasma triglyceride levels in the turtle Kinosternon scorpioides , and refeeding caused an elevation (Oliveira et al., ). Plasma NEFA levels were unchanged by the feeding protocol, while glucose levels were lower during fasting (Oliveira et al., ).…”

“…Similarly, fasting caused a drop in plasma triglyceride levels in the turtle Kinosternon scorpioides , and refeeding caused an elevation (Oliveira et al., ). Plasma NEFA levels were unchanged by the feeding protocol, while glucose levels were lower during fasting (Oliveira et al., ). Red‐eared sliders ( Trachemys scripta ) had elevated plasma triglyceride levels following feeding, in association with an increase in the amount of VLDL and enteromicron‐sized lipoproteins (Cain et al., ).…”

“…These lipid stores then decline during winter dormancy, particularly in the fat bodies (Souza et al., ; Haddad, ). Similarly, both liver lipids and glycogen were consumed during long‐term fasting in the turtle Kinosternon scorpioides (Oliveira et al., ). Lipid content of both the fat bodies and tail was reduced during winter dormancy in Zootoca ( Lacerta ) vivipara (Avery, ).…”

“…Oliveira et al . () studied the effects of fasting and refeeding in the turtle Kinosternon scorpioides . There was a loss of liver glycogen but not muscle glycogen over the fasting period, particularly at the beginning, and a concurrent drop in plasma glucose levels during the fast.…”

“…There was a loss of liver glycogen but not muscle glycogen over the fasting period, particularly at the beginning, and a concurrent drop in plasma glucose levels during the fast. Plasma urea concentration declined during the fast, implying reduced protein oxidation, and this rebounded upon refeeding (Oliveira et al., ). Levels of liver lipids declined only after extended fasting (60 days), but plasma triglyceride levels declined at least as early as 15 days into fasting.…”