Physiological Tradeoffs of Immune Response Differs by Infection Type in Pieris napi.

Lucie Kučerová,Christopher W Wheat,Naomi L P Keehnen,Sören Nylin,Ulrich Theopold

doi:10.3389/fphys.2020.576797

Abstract

Understanding the tradeoffs that result from successful infection responses is central to understanding how life histories evolve. Gaining such insights, however, can be challenging, as they may be pathogen specific and confounded with experimental design. Here, we investigated whether infection from gram positive or negative bacteria results in different physiological tradeoffs, and whether these infections impact life history later in life (post-diapause development), in the butterfly Pieris napi. During the first 24 h after infection (3, 6, 12, and 24 h), after removing effects due to injection, larvae infected with Micrococcus luteus showed a strong suppression of all non-immunity related processes while several types of immune responses were upregulated. In contrast, this tradeoff between homeostasis and immune response was much less pronounced in Escherichia coli infections. These differences were also visible long after infection, via weight loss and slower development, as well as an increased mortality at higher infection levels during later stages of development. Individuals infected with M. luteus, compared to E. coli, had a higher mortality rate, and a lower pupal weight, developmental rate and adult weight. Further, males exhibited a more negative impact of infection than females. Thus, immune responses come at a cost even when the initial infection has been overcome, and these costs are likely to affect later life history parameters with fitness consequences.

Highlights

Pathogens and parasites exert strong selection pressures upon hosts for their survival
To determine the effect of live bacteria on survivorship and Darwinian fitness proxies, 5th instar larvae were injected with either phosphate-buffered saline (PBS) as a control, the gram-negative E. coli, or the gram-positive M. luteus, as in the previous section
On average M. luteus elicited a higher mortality than E. coli, and mortality increased with an increasing dose of both pathogens (Treatment: X2 = 34.87, df = 7, P < 0.001; Figure 1)

Summary

Introduction

Pathogens and parasites exert strong selection pressures upon hosts for their survival. Mounting an immune response is energetically costly in terms of physiology, development, and reproduction, and due to organism being limited by finite resources, often resulting in trade-offs between immune response and the other life history traits (Sheldon and Verhulst, 1996; Ahmed et al, 2002; Zuk and Stoehr, 2002; Freitak et al, 2003; Ardia et al, 2012). An energetically costly life-history trait among animals is insect metamorphosis, wherein the organism experiences a dramatic shift in their overall morphology, physiology, and often environment (e.g., from terrestrial larvae, to airborne butterfly; Russell and Dunn, 1996). Reallocating resources to fighting pathogens is expected to incur costs, to what extent variation in the type of infection mediates such tradeoffs between immune response and later life history allocation is under explored

Methods

Results

Conclusion