Abstract
Investigations focusing on host–ectoparasite interactions in animals have revealed asymptomatic to severe health and fitness consequences suggesting that species mobilize different interspecific response mechanisms. Fewer studies, however, have examined intraspecific responses to ectoparasitic burdens. In this study, we analyzed host health and fitness responses to increasing ectoparasite burdens along with the presence/absence of hemoparasites of free‐ranging insular rock iguanas (Cyclura cychlura) in The Bahamas. Using hematology, plasma biochemistry, as well as body condition and growth rate comparisons, we failed to find significant associations of tick burdens with annual growth rate, corticosterone, packed cell volume, total white blood cell, and heterophil, monocyte, eosinophil or hemoglobin measures. We did, however, find mixed and significant associations of tick burdens with lymphocyte and basophil counts, heterophil‐to‐lymphocyte ratios, and body condition indices. These associations varied by sex, size, and hemoparasite infection status suggesting that different life stages of iguanas may invest differently in immune responses, and impacts may be modulated based on size and sex of hosts, and coinfection status.
Highlights
Parasites are widespread in natural ecosystems and, by definition, infer some cost to their hosts (Watson, 2013)
No significant associations were found between total tick burden and annual growth rate, corticosterone (
Only Noddy Cay was significantly different from other sites with re‐ spect to mean feeding tick burdens (29.9 ticks, 95% CI: 26.0–33.8, Figure 2d)
Summary
Parasites are widespread in natural ecosystems and, by definition, infer some cost to their hosts (Watson, 2013). Re‐ sistance is a physiological response by the host to reduce parasitic burdens (including immunological resistance), while tolerance is the ability of a host to reduce the negative effect of infection on fitness at a set parasitic burden (Råberg et al, 2009). Each of these strate‐ gies could be influenced by predators (Marino, Holland, & Middlemis Maher, 2014), climate (Jones et al, 2016), or host traits (Comas, Ribas, Milazzo, Sperone, & Tripepi, 2014). We tested the hypothesis that there would be no growth or body condition costs associated with intensity of tick parasitism
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