Adrenal hyperplastic and degenerative changes in beluga whales

Area of Science:

• Marine Mammal Health
• Wildlife Toxicology
• Comparative Pathology

Background:

• Beluga whales (Delphinapterus leucas) in the St. Lawrence Estuary and Hudson Bay face environmental pressures.
• Adrenal gland health is a key indicator of stress and toxicological exposure in marine mammals.
• Previous studies indicate potential health issues in Canadian beluga whale populations.

Purpose of the Study:

• To investigate the prevalence and nature of adrenal gland lesions in beluga whales from two distinct Canadian populations.
• To explore potential correlations between adrenal lesions, age, and environmental factors.
• To assess the health status of beluga whales concerning adrenal gland pathology.

Main Methods:

• Post-mortem examination of adrenal glands from 30 beluga whales (St. Lawrence Estuary) and 5 beluga whales (Hudson Bay).
• Histopathological analysis to identify and quantify adrenal lesions, including hyperplasia, cysts, and degeneration.
• Statistical analysis to determine relationships between lesion severity, age, and population.

Main Results:

• Adrenal lesions were observed in 21/30 St. Lawrence Estuary belugas and 4/5 Hudson Bay belugas.
• Cortical hyperplasia was prevalent in adult St. Lawrence belugas.
• Cortisol-rich adrenal cysts and vacuolar degeneration were found in 19 whales from both populations, with increased severity in older animals.
• Medullary hyperplasia was noted in seven St. Lawrence belugas.

Conclusions:

• Adrenal lesions, including cysts and hyperplasia, are common in beluga whales and may be associated with aging.
• Potential contributing factors for adrenocortical lesions include stress and xenobiotic exposure.
• Medullary hyperplasia might be linked to hypoxia or estrogenic xenobiotics, warranting further investigation into environmental impacts on beluga health.