Blubber development in bottlenose dolphins (Tursiops truncatus)

Area of Science:

• Marine Mammal Biology
• Comparative Anatomy
• Histology

Background:

• Blubber, the hypodermis of cetaceans, is crucial for thermoregulation, buoyancy, energy storage, and locomotion.
• Understanding blubber development is key to comprehending cetacean physiology and adaptation.

Purpose of the Study:

• To investigate the ontogenetic development of bottlenose dolphin (Tursiops truncatus) blubber.
• To analyze morphological and structural changes in blubber across different life history stages.

Main Methods:

• Collected blubber samples from 25 bottlenose dolphins (fetus to adult).
• Measured blubber mass, depth, and lipid content.
• Utilized light microscopy and digital image analysis to assess adipocyte size, shape, number, and fiber density through blubber depth.

Main Results:

• Blubber mass and depth increased proportionally with body size from fetus to adult.
• Lipid content and adipocyte size significantly increased with age, particularly in postnatal stages.
• Adipocyte size increased in middle and deep blubber regions, while cell numbers remained constant.
• Emaciated adults showed lipid depletion localized to middle and deep blubber layers.

Conclusions:

• Bottlenose dolphin blubber increases in depth primarily through adipocyte hypertrophy, not hyperplasia, during postnatal growth.
• Middle and deep blubber layers are metabolically dynamic, involved in lipid storage and mobilization.
• Superficial blubber likely provides structural support for streamlining.
• Blubber is a heterogeneous tissue with depth-dependent and life history-specific characteristics.