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Immune function responds to selection for cuticular colour in Tenebrio molitor.
S A O Armitage1, M T Siva-Jothy
1Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. saoarmitage@bi.ku.dk
Heredity
|April 9, 2005
Summary
Darker mealworm beetles exhibit enhanced immune responses, suggesting a link between cuticular color and pathogen resistance. This study selected for beetle color, revealing higher immune activity in darker individuals due to shared melanin production pathways.
Area of Science:
- Evolutionary biology
- Insect immunology
- Quantitative genetics
Background:
- Cuticular color in mealworm beetles (Tenebrio molitor) varies quantitatively from tan to black.
- Darker insect cuticles are often associated with increased pathogen resistance.
- Cuticular color is a heritable trait influenced by melanin production.
Purpose of the Study:
- To investigate the correlated responses of immune effector systems to artificial selection for cuticular color in Tenebrio molitor.
- To determine if selection for darker cuticles leads to enhanced immune function.
Main Methods:
- Experimental evolution by selecting for black and tan cuticular phenotypes over at least six generations.
- Measurement of immune parameters including haemocyte density and phenoloxidase (PO) activity.
- Comparison of immune responses between selected black and tan beetle lines.
Main Results:
- Selection lines of black beetles showed significantly higher haemocyte density compared to tan lines.
- Pre-immune challenge activity of phenoloxidase (PO) was also significantly higher in black beetle lines.
- These immune differences suggest a correlated response to selection on cuticular color.
Conclusions:
- The study provides evidence that cuticular color in Tenebrio molitor is genetically correlated with immune function.
- Shared dependence on melanin production, involving the enzyme PO, likely underlies the observed correlation.
- Darker cuticular color may confer enhanced pathogen resistance through improved immune parameters.