The legacy of past heatwaves on ‘off-host’ parasite stages: Reduced infection risk and costs in the <i>Daphnia-Pasteuria</i> system
Bibliographic record
Abstract
Abstract Heatwaves challenge our understanding of how environmental stressors reshape host-parasite interactions, particularly during the critical “off-host” stages of endoparasites. These stages, often dismissed as inert and unaffected by environmental changes, remain a black box in ecological research despite their key role in parasites’ life cycle. Here, we examined how heatwaves affect the infectivity and progression of infection of Pasteuria ramosa, a bacterial parasite of the planktonic crustacean Daphnia magna. In order to measure the respective influences of the bacterial genotype and the heatwaves, we exposed the off-host stages (=spores) from four genetically distinct parasite clones to three temperature regimes (20°C, 30°C, 40°C), and tested their subsequent effects on host and parasite traits. Heatwaves reduced parasite infectivity, regardless of parasite genotype. Intriguingly, heat-stressed spores induced genotype-specific shifts in their host: one host clone increased castration rates at higher temperatures, while others experienced moderate to dramatic declines. Furthermore, individuals exposed to heat-stressed spores that remained uninfected, exhibited enhanced survival, suggesting reduced costs of resistance against damaged parasite spores. This study provides insights into how heatwaves, endured only by the parasite, can modulate various aspects of host-parasite interactions, underlying the importance of the parasite’s environmental history in evolutionary ecology and epidemiology. Open Research Statement All data and code supporting the results of this study are provided here: https://github.com/JustineBoutry/HeatwaveSpores
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".