Effects of energy mobilization during fasting and lactation on plasma metabolites in the grey seal ( Halichoerus grypus)

Abstract

1. 1. The effects of fasting and lactation on plasma metabolites and insulin as well as morphometric parameters related to the mobilization of energy reserves were investigated in grey seals ( Halichoerus grypus) of different ages and sex during the 4 week terrestrial breeding period on Sable Island, NS, Canada. 2. 2. Clear differences in body length and girth between the sexes were already recognizable in juveniles. Fasting and lactation caused a marked decrease in adipose tissue thickness and girth in lactating females. At the same time, there was a considerable increase in body weight, blubber thickness and girth in sucking pups. 3. 3. The level of lipids and free fatty acids were much higher compared to terrestrial species and were clearly affected by lactation and sucking. The onset of lactation caused a marked decrease in total lipids (basically triglycerides). 4. 4. In sucklings, the level of lipids was much higher (mainly triglycerides) than in weaned ones, whereas phospholipids and cholesterol increased with the post-weaning fast. 5. 5. Glucose levels in blood were higher in grey seals of all ages (> 1.2g/l) than in terrestrial mammals. No obvious differences related to the metabolic changes were observed. 6. 6. Contrary to other species, glucose and glycerol were higher in the blood of the fetus than in the blood of the mother. 7. 7. The high concentrations of glucose and glycerol and the lack of ketone bodies in the blood plasma of adult seals during fasting suggests a possible utilization of acetone for gluconeogenesis.