Baby Seal

Surfactant Composition
When compared to terrestrial mammals (cow, sheep, pigs, humans), California sea lions (Zalophus californianus), Northern elephant seals (Mirounga angusturistris), Ringed seals (Phoca hispida), and Harbor seals (Phoca vitulina) had lower levels of the anionic surfactant phospholipids (phosphatidyldlycerol and phosphatidylinositol). Although the role of PG and PI are not clear, they appear to interact with hydrophobic surfactant proteins SP‐B and SP‐C to prevent the irreversible removal of the phospholipids from the surfactant film during alveolar compression and collapse for rapid reinsertion upon reexpansion. There is a also greater percentage of short fatty acid phosphatidylcholine, the primary phospholipid contributor to surfactant function, in pinnipeds than in terrestrial mammal. Since fluidity of the surfactant mixture is also dependent on fatty acid tail length where length leads to increased surfactant fluidity, the change in tail length may indicate a surfactant system adaptation in response to the selection for an effective anti‐adhesive surfactant in collapsed lungs of diving pinnipeds.