@article {3599,
	title = {Ectoparasite load is linked to ontogeny and cell-mediated immunity in an avian host system with pronounced hatching asynchrony},
	journal = {Biological Journal of the Linnean Society},
	volume = {94},
	number = {3},
	year = {2008},
	month = {July},
	pages = {463-473},
	type = {Article},
	abstract = {Several contrasting hypotheses have been proposed to account for host age-biased parasite distribution, with some of them suggesting a key role of ectoparasites in the evolution and maintenance of weight hierarchies within broods. We examined parasite distribution among individual hosts across the whole period of host exposure to the parasite in a host system that shows distinct within-brood differences in age and age-related mortality. By contrast to previous hypotheses, we found that the abundance of a haematophagous, mobile ectoparasite Carnus haemapterus on nestling European rollers (Coracias garrulus) was highest approximately during the mid-nestling stage of their host, coinciding with the inflection point of the host growth phase. Parasite load increased neither with absolute resource availability (i.e. body size), nor body condition index. By contrast to previous evidence, higher parasite load under natural conditions was associated with a stronger cell-mediated immune response. However, this association was moderated by low parasite densities, as well as a better brood body condition index. Overall, although we revealed remarkable host ontogenetic effects on parasite distribution, the present study suggests that a highly mobile ectoparasite generally prefers healthier hosts. We propose that, in host systems with a marked asynchrony of hatching and background mortality within the brood, parasites favour persistence rather than nutritional attractiveness of the host. (C) 2008 The Linnean Society of London.
},
	keywords = {Carnus hemapterus, Europe},
	isbn = {0024-4066},
	url = {<Go to ISI>://ZOOREC:ZOOR14409054805 },
	author = {Vaclav, Radovan and Calero-Torralbo, Miguel A. and Valera, F.}
}
@article {2060,
	title = {Origin-related, environmental, sex, and age determinants of immunocompetence, susceptibility to ectoparasites, and disease symptoms in the barn owl},
	journal = {Biological Journal of the Linnean Society},
	volume = {90},
	number = {4},
	year = {2007},
	month = {April},
	pages = {703-718},
	abstract = {Knowledge of the role of origin-related, environmental, sex, and age factors on host defence mechanisms is important to understand variation in parasite intensity. Because alternative components of parasite defence may be differently sensitive to various factors, they may not necessarily covary. Many components should therefore be considered to tackle the evolution of host-parasite interactions. In a population of barn owls (Tyto alba), we investigated the role of origin-related, environmental (i.e. year, season, nest of rearing, and body condition), sex, and age factors on 12 traits linked to immune responses (humoral immune responses towards sheep red blood cells (SRBC), human serum albumin (HSA) and toxoid toxin TT, T-cell mediated immune response towards the mitogen phytohemagglutinin (PHA)), susceptibility to ectoparasites (number and fecundity of Carnus haemapterus, number of Ixodes ricinus), and disease symptoms (size of the bursa of Fabricius and spleen, proportion of proteins that are immunoglobulins, haematocrit and blood concentration in leucocytes). Cross-fostering experiments allowed us to detect a heritable component of variation in only four out of nine immune and parasitic parameters (i.e. SRBC- and HSA-responses, haematocrit, and number of C. haemapterus). However, because nestlings were not always cross-fostered just after hatching, the finding that 44\% of the immune and parasitic parameters were heritable is probably an overestimation. These experiments also showed that five out of these nine parameters were sensitive to the nest environment (i.e. SRBC- and PHA-responses, number of C. haemapterus, haematocrit and blood concentration in leucocytes). Female nestlings were more infested by the blood-sucking fly C. haemapterus than their male nestmates, and their blood was less concentrated in leucocytes. The effect of year, season, age (i.e. reflecting the degree of maturation of the immune system), brood size, position in the within-brood age hierarchy, and body mass strongly differed between the 12 parameters. Different components of host defence mechanisms are therefore not equally heritable and sensitive to environmental, sex, and age factors, potentially explaining why most of these components did not covary.
},
	keywords = {Carnidae, Carnus, Carnus hemapterus},
	isbn = {0024-4066},
	url = {<Go to ISI>://ZOOREC:ZOOR14402011278 },
	author = {Roulin, A. and Christe, Philippe and Dijkstra, Cor and Ducrest, Anne-Lyse and Jungi, Thomas W.}
}
