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The good genes hypothesis of sexual selection postulates that ornamentation signals superior genetic quality to potential mates. Support for this hypothesis comes from studies on male ornamentation only, while it remains to be shown that female ornamentation may signal genetic quality as well. Female barn owls (Tyto alba) display more black spots on their plumage than males. The expression of this plumage trait has a genetic basis and it has been suggested that males prefer to mate with females displaying more black spots. Given the role of parasites in the evolution of sexually selected traits and of the immune system in parasite resistance, we hypothesize that the extent of female plumage`spottiness' re£ects immunological defence. We assessed the genetic variation in speci¢c antibody production against a non-pathogenic antigen among cross-fostered nestlings and studied its covariation with the plumage spottiness of genetic parents. The magnitude of the antibody response was positively correlated with the plumage spottiness of the genetic mother but not of the genetic father. Our study thereby provides the ¢rst experimental support, to our knowledge, for the hypothesis that female ornamentation signals genetic quality.

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Background: Inflammatory bowel disease (IBD) is thought to result from a dysregulated interaction between the host immune system and commensal microflora. Toll-like receptors (TLRs) recognize microbe-associated molecular patterns (MAMPs), but their role in enteropathies in dogs is unknown.Hypothesis: That there is a dysregulation of TLRs recognizing bacterial MAMPs in dogs with IBD. Animals: Sixteen healthy beagles and 12 dogs with steroid-treated (ST) and 23 dogs with food-responsive (FR) diarrhea. Methods: Prospective, observational study. mRNA expression of canine TLR2, 4, and 9 was evaluated by quantitative realtime RT-PCR in duodenal and colonic biopsies obtained before and after standard therapy. Samples from control dogs were taken at necropsy, with additional biopsies of stomach, jejunum, ileum, and mesenteric lymph node in 6 dogs.Results: There were significant differences (P .017) in expression of TLR2, 4, and 9 between the 6 sampled locations in healthy control dogs (lymph node 4 small intestine ! colon). Before therapy, ST expressed more mRNA than control dogs for all 3 receptors (P o .05). There were no significant differences between pretreatment and posttreatment values, even though 32/ 35 dogs improved clinically. No associations were found when comparing receptor mRNA expression with either histology or clinical activity scores.Conclusions and Clinical Importance: Bacteria-responsive TLR2, 4, and 9 are upregulated in duodenal and colonic mucosa in IBD. This might lead to increased inflammation through interaction with the commensal flora. The absence of significant changes after therapy despite clinical improvement might point toward the existence of a genetic predisposition to IBD as described in human IBD.

Summary1. The Tasty Chick Hypothesis (TCH) proposes that hatching asynchrony evolved as an antiparasite strategy. Hosts would benefit if ectoparasites aggregate more on the offspring that are of lowest reproductive value within a brood, i.e. on the last-hatched chicks, because offspring reproductive value generally decreases with hatching rank. The poor body condition of the later-hatched chicks would impair parasite resistance and render them especially attractive to ectoparasites. Thus, the TCH predicts a decline in chick parasite load with hatching order in avian broods. 2. We investigated the main assumption of the TCH that junior chicks are less immunocompetent than their senior siblings. We also examine the prediction of the TCH that junior chicks bear more ectoparasites than their senior siblings. 3. Conform to the assumption of the TCH for hosts, junior chicks in broods of the barn owl ( Tyto alba L.) showed a lower humoral immune response than their senior siblings. In contrast, the cell-mediated immune response of senior chicks in broods of the great tit ( Parus major L.) was not significantly greater than that of their junior siblings. 4. In line with the prediction of the TCH for the distribution of parasites among hosts, the fly Carnus haemapterus Nitzsch infested junior chicks in larger numbers than senior chicks in both barn owl and kestrel ( Falco tinnunculus L.) broods. 5. In conflict with the TCH, ticks ( Ixodes ricinus L.) were distributed randomly with respect to hatching rank in broods of the barn owl and the great tit. Moreover, louseflies Crataerina melbae Rondani infested mainly senior chicks instead of junior chicks in the Alpine swift ( Apus melba L.). 6. Summarizing, the present descriptive study indicates that the distribution of ectoparasites within-broods is not generally governed by rank-related variation in host defence of chicks as initially suggested by the TCH. We argue that specific aspects of the morphology, life history and ecological requirements of various ectoparasite species need more consideration as to explain the dynamics and evolution of host-parasite interactions.

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Summary Toll‐like receptors (TLR) have been described as partially sharing signalling pathways but showing unique ligand specificity and tissue distribution. Here, the response of bovine macrophages (Mφ) and dendritic cells (DC), both derived from monocytes, was compared by exposing them to the TLR‐specific ligands lipopolysaccharide, poly(I:C)‐double‐stranded RNA, and CpG‐DNA, as well as inactivated Gram‐negative and Gram‐positive bacteria, shown to bind to TLR. The production of NO, superoxide anion, interleukin‐10 (IL‐10), IL‐12 and tumour necrosis factor (TNF) was determined. Compared to monocytes, Mφ expressed more TLR2 and similar levels of TLR4 mRNA transcripts, as analysed by quantitative polymerase chain reaction, whereas DC expressed reduced amounts. Although both DC and Mφ recognized the TLR ligands, dramatic differences were seen in their reaction pattern to them. Both cell types responded with the production of TNF, but DC produced more IL‐12, whereas Mφ produced more IL‐10, regardless of the TLR agonist used. Co‐stimulation with interferon‐γ influenced the amount of cytokine production, but did not alter the cell type‐specific response pattern. Compared to Mφ, DC produced > 10 times less NO upon triggering with TLR ligands. In addition, DC produced superoxide anion to opsonized and non‐opsonized zymosan, but not to phorbol 12‐myristate 13‐acetate, a response pattern confirmed for human Mφ and DC, respectively. Different protein kinase C isoforms and extracellular signal‐regulated kinase patterns were detected in cell lysates of resting and stimulated Mφ and DC. Collectively, our results point to profound differences in pathogen‐derived signal–response coupling occurring commensurate with distinct functions carried out by Mφ or DC.