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Covariation between brain size and immunity in birds: implications for brain size evolution
A P Møller1, J Erritzøe, L Z Garamszegi
1Laboratoire de Parasitologie Evolutive, CNRS UMR 7103, Université Pierre et Marie Curie, Paris Cedex 05, France. amoller@snv.jussieu.fr
Journal of Evolutionary Biology
|January 27, 2005
Summary
In birds, larger relative brain size in males is linked to larger immune organs, suggesting a coevolutionary relationship between brain size and immunity to combat parasites.
Area of Science:
- Comparative immunology
- Neuroscience
- Evolutionary biology
Background:
- Parasitism negatively impacts cognition and learning.
- Males may be more susceptible to parasites, potentially affecting cognitive abilities.
- Immune system investment may compensate for parasite susceptibility, especially in species with larger male brains.
Purpose of the Study:
- To investigate the covariation between the relative size of immune defense organs and brain size in birds.
- To explore sex differences in the relationship between immune organ size and brain size.
Main Methods:
- Analysis of the relative sizes of immune defense organs (bursa of Fabricius, spleen) and brain in juvenile and adult birds.
- Comparison across different bird species.
- Examination of covariation with sex differences in relative brain size.
Main Results:
- The relative size of the bursa of Fabricius and spleen in adult birds positively covaried with relative brain size.
- These immune organs' sizes covaried with sex differences in relative brain size, indicating a stronger relationship in males.
- Liver and heart size, and sexual size dimorphism, did not covary with immune defense.
Conclusions:
- Species with relatively larger male brains also exhibit relatively larger immune defense organs.
- This suggests a coevolutionary link between brain size and immune system investment, particularly in males, to manage parasite load.
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