Fig. 8. Hypothesized model for the organization of lipids in the intercellular spaces of the SC in house sparrows from mesic and desert environments. In sparrows, lamellae would be formed by three layers of lipids; two outer layers consisting of ceramides, and an inner layer formed by cerebrosides and free fatty acids. Ceramides would form a highly ordered structure, whereas the inner layer would be more fluid. In this model, we assume that the chain lengths of free fatty acids would be the same between desert and mesic individuals.