More Urban Roads Linked to Gut Damage in Social Bees

Greg Howard
7th July, 2024

More Urban Roads Linked to Gut Damage in Social Bees

In contrast to the healthy tissue from bees in greener areas (e–h), the midgut epithelium of Halictus scabiosae from urbanized sites shows severe cellular damage, including a high frequency of fragmented, dying nuclei (karyorrhexis) (a), extensive vacuolization (b, d), and a damaged brush border (c).

Image adapted from: Ferrari et al. / CC BY (Source)

Key Findings

  • The study focused on Halictus scabiosae bees in Milan to examine the impact of urbanisation on their midgut health
  • Bees from more urbanised areas showed significant damage to their midgut cells, including disorganisation and cell death
  • Higher road cover, indicating more pollution, was linked to increased midgut damage, potentially impairing bees' digestive functions
Urbanisation often leads to increased air and soil pollution, particularly from heavy metals. One of the primary tissues exposed to these pollutants in insects is the midgut epithelium, as pollutants are ingested with food. Bees, crucial urban insects, provide essential ecosystem services such as pollination. However, there has been limited research on the potential histological alterations in the midgut epithelium of bees caused by urbanisation. A recent study by the University of Milan[1] aimed to fill this gap by examining workers of the ground-nesting, primitively eusocial bee Halictus scabiosae in Milan. The researchers hypothesized that bees from areas with higher urbanisation and consequently higher pollution levels—characterised by a greater proportion of roads—would exhibit more significant histological tissue and cellular alterations in the midgut epithelium. Using histological techniques, they obtained semi-thin sections of the midgut and adopted a semi-quantitative approach to assess morphological damage. The study found a range of histological alterations, including epithelium disorganisation, vacuolisation (formation of vacuoles within the cell), and nucleus karyorrhexis (a stage of cellular death). Sites with a higher proportion of roads showed a higher histological damage score and frequency of karyorrhectic nuclei, suggesting a potential impairment of the digestive function in bees from highly urbanised areas. These findings are significant as they highlight the potential adverse effects of urbanisation on bee health, which could have broader implications for ecosystem services such as pollination. The study's results align with previous research on other insects. For instance, a study on common wasps (Vespula vulgaris) found that wasps from highly polluted environments exhibited morphological changes and metal particles in their guts, encapsulated with melanin pigment, indicating a phenotypic response to pollution[2]. Similarly, another study on bumble bees (Bombus spp.) across an urban gradient in Saint Louis, Missouri, found that some species exhibited body size clines despite a lack of population genetic structure, suggesting that plasticity can cause phenotypic changes across human-modified landscapes[3]. The University of Milan study provides new insights into the specific histological alterations in bees due to urbanisation. By focusing on the midgut epithelium, the researchers were able to identify tangible cellular changes that could affect bee health and their ability to perform essential ecological roles. This study underscores the importance of considering urbanisation's impact on pollinators and adds to the growing body of evidence that environmental contamination can lead to significant phenotypic and histological changes in insects. In conclusion, the study by the University of Milan highlights the detrimental effects of urbanisation on the midgut epithelium of Halictus scabiosae bees, with potential implications for their digestive function and overall health. These findings contribute to our understanding of how urban environments impact insect physiology and underscore the need for further research and conservation efforts to mitigate these effects. The study also aligns with previous research on the phenotypic plasticity of insects in polluted environments[2][3], further emphasizing the complex relationship between urbanisation and insect health.

EnvironmentEcologyAnimal Science

References

Main Study

1) Increasing road cover in urban areas is associated with greater midgut histological damage in a primitively eusocial bee

Published 4th July, 2024

https://doi.org/10.1007/s00040-024-00980-5

Related Studies

2) Phenotypic Plasticity of Common Wasps in an Industrially Polluted Environment in Southwestern Finland.

https://doi.org/10.3390/insects12100888

3) Bumble bees exhibit body size clines across an urban gradient despite low genetic differentiation.

https://doi.org/10.1038/s41598-022-08093-4


Related Articles

An unhandled error has occurred. Reload 🗙