Costly parasite resistance: a genotype-dependent handicap in sand lizards?
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Olsson, M and Wapstra, E and Madsen, T and Ujvari, B and Rugfelt, C, Costly parasite resistance: a genotype-dependent handicap in sand lizards?, Biology Letters, 1, (3) pp. 375-377. ISSN 1744-9561 (2005) [Refereed Article]
Male sand lizards (Lacerta agilis) with a specific restriction fragment length polymorphism fragment in their major histocompatibility complex (MHC) genotype ('O-males') are more resistant to ectoparasites (a tick, Ixodes ricinus) than are males that lack this fragment ('NO-males'). However, emerging evidence suggests that such adaptive immune responses are costly, here manifested by reduced body condition and a compromised defence against secondary infections by haemoprotid parasites that use the ticks as vectors. Subsequent to tick encounter, O-males suffer from a higher leucocyte-erythrocyte ratio, and higher haemoprotid parasitaemia, in particular in relation to vector encounter rate. Furthermore, O-males (i.e. successful tick defenders) with more haemoprotid parasites remaining in their blood stream were in better body condition, whereas this did not apply in NO-males, demonstrating that the adaptive immunoreaction can-in the short term-be energetically even more costly than being moderately parasitized. In agreement with Zahavian handicap theory, O-males had a (marginally) higher reproductive success than males that lacked this fragment. © 2005 The Royal Society.
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