Evol Ecol Res 16: 593-603 (2014)     Full PDF if your library subscribes.

Immune responses vary with parasite burden in an insular lizard

Mario Garrido and Valentín Pérez-Mellado

Department of Animal Biology, University of Salamanca, Campus Unamuno, Salamanca, Spain

Correspondence: M. Garrido, Department of Animal Biology, University of Salamanca, Campus Unamuno, 37007 Salamanca, Spain.
e-mail: gaiarrido@usal.es

ABSTRACT

Background: Immunological studies are often context-independent. However, an alternative is emerging in the form of eco-immunology, which focuses on the natural variation in immune functions of free-living organisms in relation to their ecological constraints and evolutionary context. Immunological research also tends to study only parasite resistance – that is, mechanisms by which hosts prevent infection or reduce parasite growth. But eco-immunology addresses tolerance as well as resistance. Through tolerance, hosts defend themselves by minimizing the damage caused by parasites instead of reducing parasite infection.

Goal: To determine the immune responses of free-living lizards that have varying parasite loads and body conditions.

Organism: A wild, insular population of Podarcis lilfordi.

Method: Immune response was measured as the bactericidal strength of plasma, and the immune response was examined with respect to parasite load and to body condition.

Results: Immune responses were affected by an interaction between parasite load and body condition. In lightly infected lizards, the immune response was positively correlated with body condition. But in heavily infected lizards, this correlation was not evident. Individuals in the population studied seem to exhibit different strategies of parasite defence. Some appear to resist parasite infection, whereas others rely on tolerance.

Keywords: bacterial killing assay, haemogregarine, immune response, immunological strategies, insularity, parasitic infestation, resistance, tolerance.

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