Characterising grey seals' blubber structure

Accurate regulation of energy stores is linked to reproductive success and survival. Fat deposition and mobilisation has been associated with changes in adipocyte size and number, extracellular matrix deposition, vascularity among other adaptations in other mammals. How seals’ blubber adjusts with rapid body composition changes is unknown. Biopsy samples from mother and pup pairs (n = 6) were collected at early, late and pup’s early weaning lactation. Samples were processed and stained with Masson’s Trichrome. Biopsies were divided in three sections: inner, middle and outer blubber. Five microphotographs of each section were taken to be averaged. Adipocyte size/ number, collagen area and blood vessels were measured with Image J and Adiposoft plugin. Linear mixed models were used to investigate variation in relation to weight, depth and metabolic state with in each age class and comparison between fasting mums and pups. Preliminary results showed that, consistently with other mammals, adipocyte size increased with weight as adipocyte number per picture is reduced. Collagen area decreased in late lactation and weaning in pups, but not mum. Vascularity was not significantly associated to any measured variable. According to preliminary results, grey seals’ blubber structure is not stratified and only adipocytes vary with weight changes.