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Age-related mushroom body expansion in male sweat bees and bumble bees

Summary

Researchers studied how male bee brains change as they mature using microscopy to measure brain structures. They found that mushroom bodies, regions associated with learning and memory, expanded significantly in maturing males of two bee species even when kept in isolation without normal experiences. This suggests that brains naturally prepare for mating behaviors through development rather than requiring experience, and shows that male insects undergo similar brain changes as females.

Background

Brain changes in social insects often occur prior to or at the onset of specific experiences, potentially priming the brain for particular tasks. However, previous research on age-related brain plasticity has focused almost exclusively on females, leaving unclear whether these patterns are consistent across sexes.

Objective

To investigate age-related brain changes coinciding with sexual maturation in males of two bee species: the facultatively eusocial sweat bee Megalopta genalis and the obligately eusocial bumble bee Bombus impatiens, using confocal microscopy and volumetric analyses.

Results

Both species showed significant age-related expansion of mushroom bodies with maturation. M. genalis exhibited 16.6% larger calyces and 14.7% larger total mushroom body neuropil in mature males. B. impatiens showed 24.5% larger calyces and 19.5% larger neuropil in mature males. Neuropil:Kenyon cell ratios were significantly higher in mature males of both species.

Conclusion

Age-related mushroom body expansion occurs during reproductive maturation in male bees independent of ecologically-relevant experience, suggesting that experience-expectant neuroplasticity may prepare males for mating-related cognitive demands. This pattern can occur in males even when absent in females.
  • Published in:Scientific Reports,
  • Study Type:Comparative experimental study,
  • Source: PMID: 34426595, DOI: 10.1038/s41598-021-96268-w
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