Natural variation in host defense strategies impacts both host and pathogen fitness
Bibliographic record
Abstract
Summary Animals ranging from mosquitoes to humans often vary their feeding behavior when infected or merely exposed to pathogens. For example, some individuals drastically reduce their food intake (‘illness-mediated anorexia’) while others increase food intake (‘hyperphagia’). While these so-called ‘sickness behaviors’ are well documented, their functional consequences remain poorly resolved. Here, we examine links between natural genetic variation in susceptibility to infection, feeding behaviors, multiple traits of the host, and within-host pathogen production. Using a zooplankton host ( Daphnia dentifera ) and a fungal pathogen ( Metschnikowia bicuspidata ) as a case study, we show that genotypic and dose-dependent variation in feeding behaviors are associated with both resistance and tolerance mechanisms. In one genotype, immune-mediated anorexia was associated with increased tolerance to infection; unlike other genotypes, these individuals did not upregulate phenoloxidase activity, but lived longer, had the highest overall fecundity, and produced higher pathogen loads, despite their reduced growth rates and resultant smaller body sizes. In these hosts, peak parasite load remained unchanged, suggesting a tolerance mechanism that offset fecundity costs. In other genotypes, feeding behaviors followed either a flat or hump-shaped pattern with pathogen dose, exhibiting hyperphagia at intermediate doses and anorexia at higher doses. In these cases, anorexia functioned primarily in resistance. Our results suggest that infection-mediated changes in host feeding behavior — which are traditionally interpreted as immunopathology — may in fact serve as crucial components of host defense strategies. Moreover, these phenomena vary across host genotypes, and were associated with apparent trade-offs with another melanization component of immune defense. Together, these results underscore that while resistance and tolerance are typically viewed as alternative and fixed defense strategies, the immense genetic diversity for immune defense may result in more of a plastic spectrum spanning a gradient from resistance to tolerance.
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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 | 0.000 |
| 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".