Figure 4. At the ultrastructural level, lipids (L) appeared as electrodense droplets within the myofibrils, closely related to the mitochondria (arrowheads), which were bigger and less electrodense in the deep-diving species.

(A) Adult female of blainville’s beaked whale (Mesoplodon densirostris). (B) Adult specimen of Atlantic spotted dolphin (Stenella frontalis). Bar = 1 μm.