Blubber structure of finless porpoises. (A) A longitudinal section through the blubber layer at the ventral aspect of the umbilicus region. Longitudinal blubber images at the (B) dorsal, (C) lateral, and (D) ventral aspects of the umbilicus region, respectively. Lines with double-headed arrows indicate blubber depth; the arrows indicate the skin layer. AC, abdominal cavity; DB, deep blubber layer; IB, inner blubber layer; M, muscle layer; MB, middle blubber layer; OB, outer blubber layer; SB, superficial blubber layer. Scale marks are in centimeters.