Immune System Changes in Roundworms After Exposure to Radiation

Jenn Hoskins
12th July, 2024

Immune System Changes in Roundworms After Exposure to Radiation

Image Source: Natural Science News, 2024

Key Findings

  • The study, conducted by IRSN, examined the effects of gamma radiation on the fitness and host defense of Caenorhabditis elegans over 20 generations
  • Populations exposed to higher levels of radiation showed reduced fitness compared to control populations, but their fitness improved over time
  • When exposed to a bacterial parasite, irradiated populations had lower survival rates, indicating a trade-off between radiation adaptation and host defense capabilities
Adaptation to stressors can lead to significant costs on other traits, impacting the overall fitness and evolutionary pathway of a population. Host defense, in particular, is highly susceptible to these costs due to its energy-intensive nature, which is crucial for survival. When evaluating the ecological risks associated with pollution, it is essential to consider these costs to understand the evolutionary consequences on populations. A recent study conducted by the Institut de Radioprotection et de Sûreté Nucléaire (IRSN)[1] sheds light on the effects of evolution in irradiated environments on host defense, a topic that has not been extensively studied. The IRSN study aimed to analyze the fitness of Caenorhabditis elegans populations across 20 generations when exposed to varying levels of 137Cs gamma radiation (0, 1.4, and 50.0 mGy.h−1). Following 17 transfers under these conditions, the populations were then placed in a common environment without irradiation for about 10 generations. Subsequently, these populations were exposed to the bacterial parasite Serratia marcescens to estimate their host defense capabilities. The study sought to uncover any evolutionary trade-offs between the fitness of irradiated populations and their host defense mechanisms. The findings of this study are particularly relevant when contextualized with previous research. For instance, earlier studies have shown that adaptation to specific environmental stressors often comes with trade-offs in other environments. One notable study[2] demonstrated that Escherichia coli lineages adapted to low temperatures exhibited a general decline in fitness at higher temperatures. However, this trade-off was not universal, indicating that some lineages could adapt without significant fitness costs in other environments. Similarly, another study[3] on Caenorhabditis elegans exposed to uranium and salt stressors revealed that adaptive evolution could lead to either adaptive costs or benefits when encountering different stressors. In the IRSN study, the results indicated that populations exposed to higher levels of radiation showed a reduction in fitness when placed in a non-irradiated environment. This aligns with previous findings[3] that populations adapted to specific pollutants exhibited lower fitness when returned to their original environment. Furthermore, when these irradiated populations were exposed to the bacterial parasite, their survival rates were assessed to determine the impact on host defense. The study found that adaptation to radiation resulted in a trade-off, where the fitness benefits gained under irradiated conditions were offset by a decrease in host defense capabilities. This observation is consistent with another study[4] on Daphnia magna, which showed that resistance to the pesticide carbaryl led to increased susceptibility to parasite infection. The IRSN study extends these findings by demonstrating that similar trade-offs occur with radiation exposure, emphasizing the need to consider host defense costs in ecological risk assessments. Moreover, the IRSN study also highlights the importance of understanding latent costs associated with adaptation. Previous research on Biomphalaria glabrata[5] showed that while no immediate fitness costs were apparent under control conditions, latent costs emerged as decreased tolerance to secondary stressors. Similarly, the IRSN study found that while irradiated populations might not exhibit immediate fitness costs, their reduced host defense capabilities represent a latent cost that could impact their long-term survival. In summary, the IRSN study contributes valuable insights into the evolutionary trade-offs associated with adaptation to irradiated environments. By demonstrating that fitness benefits under specific stressors can lead to decreased host defense capabilities, the study underscores the importance of considering these costs in ecological risk assessments. The findings align with and expand upon previous research on trade-offs in different environmental conditions, highlighting the complex interplay between adaptation and fitness in evolving populations.

GeneticsAnimal ScienceEvolution

References

Main Study

1) Host defense alteration in Caenorhabditis elegans after evolution under ionizing radiation

Published 9th July, 2024

https://doi.org/10.1186/s12862-024-02282-7

Related Studies

2) An experimental test of evolutionary trade-offs during temperature adaptation.

Journal: Proceedings of the National Academy of Sciences of the United States of America, Issue: Vol 104 Suppl 1, Issue Suppl 1, May 2007

3) Adaptation costs to constant and alternating polluted environments.

https://doi.org/10.1111/eva.12510

4) Collateral damage: rapid exposure-induced evolution of pesticide resistance leads to increased susceptibility to parasites.

https://doi.org/10.1111/j.1558-5646.2011.01331.x

5) Adaptive responses and latent costs of multigeneration cadmium exposure in parasite resistant and susceptible strains of a freshwater snail.

https://doi.org/10.1007/s10646-010-0532-x


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