Blubber is a specialized form of adipose carried by cetaceans for the primary purposes of thermoregulation and energy storage. It constitutes a large portion of animal mass, such that a “normal” cetacean would be considered “obese” by terrestrial standards. In terrestrial mammals, adipose tissue plays a key physiological and signalling role in energy metabolism and consequently energy allocation to life functions such as survival and reproduction. Adipose plays a more complex role in the physiology of cetaceans, and recent phylogenomic work shows that we cannot expect adipose signalling to function in the same manner as in terrestrial mammals (Derous et al.) despite signals being similar (Leptin; Ball et al. 2017). Preliminary work also shows that the dolphin plasma metabolomic profile changes rapidly under fasting and that lipids play a key role in this rapid response (Houser et al.).
We need to understand how changes in adipose affect the life functions of dolphins for two reasons. Firstly, repeated foraging disruptions are becoming a conservation threat for dolphins as human activities at sea intensify and diversify. To manage this conservation impact, we need to understand how adipose signalling mediates these disruptions to affect the ability of individual dolphins to contribute to their population. Secondly, dolphins can maintain a healthy phenotype despite carrying a large adipose deposit. Understanding the role of adipose signalling in energy metabolism in this species has the potential to provide new biological insights on how to combat metabolic syndromes associated with obesity.
This study will develop experiments in a controlled environment, using a unique managed population of bottlenose dolphins, with known pedigrees, hosted by the National Marine Mammal Foundation. This unique population provides the opportunity to investigate genomic association with fasting response as well as adipose transcriptional changes in response to this short-term foraging challenge.
In addition to molecular observations of the adipose biology, the study will integrate genomic and transcriptomic information to phenotypic data collected on the same individuals at a physiological and behavioural scale. The aim will be to use state-of-the-art analytical approaches to integrate this information obtained at different biological scales in order to understand how adipose signalling influences other organs to affect energy metabolism and ultimately life function decisions.
Ball et al. 2017. J. Comp Phys B. 187 : 235-252
Derous, Sahu, Douglas & Lusseau (to be submitted) Evolution of the metabolic pathways related to nutrient sensing in cetaceans?
Houser, Derous, Douglas, Sahu & Lusseau (to be submitted) Rapid change in plasma metabolomic profile in response to short-term fasting in bottlenose dolphins.