共查询到20条相似文献,搜索用时 15 毫秒
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Gloag R Fiorini VD Reboreda JC Kacelnik A 《Proceedings. Biological sciences / The Royal Society》2012,279(1734):1831-1839
Despite the costs to avian parents of rearing brood parasitic offspring, many species do not reject foreign eggs from their nests. We show that where multiple parasitism occurs, rejection itself can be costly, by increasing the risk of host egg loss during subsequent parasite attacks. Chalk-browed mockingbirds (Mimus saturninus) are heavily parasitized by shiny cowbirds (Molothrus bonariensis), which also puncture eggs in host nests. Mockingbirds struggle to prevent cowbirds puncturing and laying, but seldom remove cowbird eggs once laid. We filmed cowbird visits to nests with manipulated clutch compositions and found that mockingbird eggs were more likely to escape puncture the more cowbird eggs accompanied them in the clutch. A Monte Carlo simulation of this 'dilution effect', comparing virtual hosts that systematically either reject or accept parasite eggs, shows that acceptors enjoy higher egg survivorship than rejecters in host populations where multiple parasitism occurs. For mockingbirds or other hosts in which host nestlings fare well in parasitized broods, this benefit might be sufficient to offset the fitness cost of rearing parasite chicks, making egg acceptance evolutionarily stable. Thus, counterintuitively, high intensities of parasitism might decrease or even reverse selection pressure for host defence via egg rejection. 相似文献
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Many hosts of obligate brood parasites accept parasitic eggs despite the high costs of parasitism. Acceptance is particularly
perplexing in brown-headed cowbird (Molothrus ater) (hereafter “cowbird”) hosts because the eggs of cowbirds and most hosts do not appear to match closely in visual characteristics
detectable by humans. However, recent evidence suggests that parasite and host eggs may match in their ultraviolet (UV) reflectance,
undetectable by humans, and that birds may use UV signals for egg discrimination. We determined whether egg colour matching
in UV reflectance separates accepters and rejecters of cowbird parasitism by comparing the total UV (300–400 nm) reflectance
of the eggs of 11 host species to cowbird eggs. Eggs of three of five accepter species and five of five rejecter species differed
significantly from cowbird eggs in UV reflectance. We found no significant difference in the UV reflectance of the eggs of
three closely related pairs of accepter and rejecter species. There also was no significant difference in the UV reflectance
of cowbird eggs laid in nests of five host species, and the UV reflectance of cowbird eggs was not significantly correlated
with that of host clutches. Thus, we found no support for the UV-matching hypothesis in brown-headed cowbirds and UV reflectance
does not appear to separate accepters and rejecters of parasitism. Differences in UV reflectance between cowbird and host
eggs, however, provide potential cues for use in egg discrimination. Experimental testing is needed to determine the relative
importance of UV reflectance compared to other visual cues. 相似文献
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Antimicrobial peptides (AMPs) are multifunctional components of the innate systems of both insect and mammalian hosts of the pathogenic trypanosomatids Leishmania and Trypanosoma species. Structurally diverse AMPs from a wide range of organisms have in vitro activity against these parasites acting mainly to disrupt surface-membranes. In some cases AMPs also localize intracellularly to affect calcium levels, mitochondrial function and induce autophagy, necrosis and apoptosis. In this review we discuss the work done in the area of AMP interactions with trypanosomatid protozoa, propose potential targets of AMP activity at the cellular level and discuss how AMPs might influence parasite growth and differentiation in their hosts to determine the outcome of natural infection. 相似文献
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It has been suggested that individual recognition based on song may be constrained by repertoire size in songbirds with very large song repertoires. This hypothesis has been difficult to test because there are few studies on species with very large repertoires and because traditional experiments based on the dear enemy effect do not provide evidence against recognition. The tropical mockingbird, Mimus gilvus, is a cooperative breeder with very large song repertoires and stable territorial neighbourhoods. The social system of this species allowed us to test individual recognition based on song independently from the dear enemy effect by evaluating male response to playback of strangers, neighbours (from shared and unshared boundaries), co-males (i.e. other males in the same social group) and own songs. Although subjects did not show a dear enemy effect, they were less aggressive to co-males than to all other singers. Our results suggest that recognition in tropical mockingbirds (1) does not simply distinguish between familiar and unfamiliar singers, (2) requires a small sample of both songs and song types, (3) does not rely on individual-specific sequences of song types and (4) is not likely to rely on group-specific vocal signatures potentially available in cooperatively breeding groups. We conclude that this is a case of true recognition and suggest that the lack of a dear enemy effect in this and other species with large repertoires may relate to the role of song in mate attraction and the perception of neighbours as a threat to future paternity. 相似文献
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