The avian spleen: a neglected organ

Area of Science:

• Comparative anatomy and physiology
• Avian immunology
• Vertebrate zoology

Background:

• The avian spleen, a vital organ, is less understood than its mammalian counterpart.
• Avian spleens are proportionally smaller than mammalian spleens.
• The spleen is crucial for avian systemic immunity, especially given the lack of lymph nodes.

Purpose of the Study:

• To review and compare avian spleen functions with mammalian spleens.
• To explore the role of the avian spleen in immunity and oxygen supply.
• To discuss seasonal variations in spleen size and function from evolutionary and ecological viewpoints.

Main Methods:

• Literature review and comparative analysis of avian and mammalian spleens.
• Discussion of proposed explanations for seasonal spleen size variation.
• Identification of research gaps in avian spleen function.

Main Results:

• Avian spleens contribute to immunity similarly to mammals but have a lesser role in oxygen supply.
• Splenic erythrocyte storage, common in mammals, is not observed in birds.
• Intraspecific variation in spleen size is linked to seasonal changes in morphology and activity.

Conclusions:

• Seasonal spleen size reduction may result from receding infections and lymphoid involution.
• Evolutionary and ecological factors likely influence avian spleen function and size.
• Comprehensive studies using diverse species and modern techniques are essential for a full understanding of avian spleen functions.