Early swelling response to phytohemagglutinin is lower in older toads.

Mar Comas,Francisco Javier Zamora-Camacho

doi:10.7717/peerj.6104

Mar Comas, Francisco Javier Zamora-Camacho

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https://doi.org/10.7717/peerj.6104

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Abstract

The effects of age on performance of life-history traits are diverse, but a common outcome is senescence, an irreversible deterioration of physical and physiological capabilities of older individuals. Immune response is potentially bound to senescence. However, little is known about immune response ageing in amphibians. In this work, we test the hypothesis that amphibian early immune response is reduced in older individuals. To this end, we captured adult natterjack toads (Epidalea calamita) and inoculated them with phytohemagglutinin, an innocuous protein that triggers a skin-swelling immune response whose magnitude is directly proportional to the ability of the individual to mount an immune response. We measured early swelling immune response (corresponding to an innate-response stage) hourly, for six hours, and we calculated the area under the curve (AUC) for each individual’s time series, as a measure of immune response magnitude incorporating time. We estimated toad age by means of phalanx skeletochronology. Swelling and AUC decreased with age. Therefore, in accordance with our predictions, early immune response seems subject to senescence in these toads. Reduced ability to get over infections due to senescence of immune respose might be—together with a worse functioning of other organs and systems—among the causes of lower survival of older specimens.

Highlights

Performance of life-history traits shifts with age in most organisms (Stearns, 1992), as physiological and ethological processes change throughout organisms’ lifetime (Kirkwood & Austad, 2000)
The effect of ageing on a given trait may depend on the ontogenetic stage of organisms (Partridge & Gems, 2006)
When age and SVL were simultaneously analysed in a multiple regression on area under the curve (AUC), we detected a significant relationship of AUC with age (F1,35 = 6.195; β = −0.498; P = 0.018), but not with SVL (F1,35 = 1.474; β = 0.243; P = 0.233)

Summary

Introduction

Performance of life-history traits shifts with age in most organisms (Stearns, 1992), as physiological and ethological processes change throughout organisms’ lifetime (Kirkwood & Austad, 2000). Ageing may affect differently various life-history traits in different organisms (Jones et al, 2014), enhancing some while impairing others in the same individual, implying different genetic and physiological trade-offs (Massot et al, 2011; González-Tokman et al, 2013). The effect of ageing on a given trait may depend on the ontogenetic stage of organisms (Partridge & Gems, 2006). Processes underlying ageing are rather intricate, some common patterns can be recognized. Ageing typically results in senescence, an irreparable decay of physical and physiological conditions. How to cite this article Zamora-Camacho FJ, Comas M.

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