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Reflections on iridescent neck and breast feathers of the peacock, Pavo cristatus.

ABSTRACT: The blue neck and breast feathers of the peacock are structurally coloured due to an intricate photonic crystal structure in the barbules consisting of a two-dimensionally ordered rectangular lattice of melanosomes (melanin rodlets) and air channels embedded in a keratin matrix. We here investigate the feather coloration by performing microspectrophotometry, imaging scatterometry and angle-dependent reflectance measurements. Using previously determined wavelength-dependent refractive indices of melanin and keratin, we interpret the spectral and spatial reflection characteristics by comparing the measured spectra to calculated spectra by effective-medium multilayer and full three-dimensional finite-difference time-domain modelling. Both modelling methods yield similar reflectance spectra indicating that simple multilayer modelling is adequate for a direct understanding of the brilliant coloration of peacock feathers.

SUBMITTER: Freyer P

PROVIDER: S-EPMC6304014 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature

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Project description:BackgroundTo date, Campylobacter jejuni has not been found to be pathogenic to peafowl. The available publications show that out of a total of 44 samples tested from peafowl, this bacterium was isolated only in two cases. Eimeria pavonina infestations in the peafowl have been described, but no fatal cases have been reported yet.Case presentationThe four-year-old peacock was presented with chronic diarrhea, emaciation and weakness. Post mortem examination revealed enlarged and pale kidneys, small intestinal mucosal necrosis and thickening of intestinal wall, and pericardial effusion. The histopathological examination revealed necrotic enteritis with marked mononuclear cells infiltration associated with the presence of coccidia, additionally there was histological evidence of septicemia in liver and kidneys. Bacteria identification was based on light microscopy of the small intestine sample, culture, and biochemical tests. Further identification was based on PCR. Antimicrobial susceptibility profile was created by determination of minimal inhibitory concentration (MIC) values for 6 antimicrobial agents from 5 different classes. PCR assays were performed to detect virulence factors genes responsible for motility, cytolethal distending toxin production, adhesion and internalization. Bacteriology of the small intestine sample showed abundant growth almost exclusively of Campylobacter jejuni, resistant to ciprofloxacin, gentamycin and ampicillin. Bacteria was sensitive to Amoxicillin + clavulanic acid, tetracycline, and erythromycin. All tested virulence factors genes have been detected. The parasitological examination was performed by microscopic examination of fresh faeces and intestinal content, and revealed the moderate number of Eimeria pavonina, Histomonas meleagridis, single Capillaria spp. eggs as well Heterakis spp. like parasites.ConclusionThe above case shows that a virulent isolate of Campylobacter jejuni in combination with a parasitic invasion may cause chronic enteritis in peafowl, which most likely led to extreme exhaustion of the host organism and death.

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Reflections on iridescent neck and breast feathers of the peacock, Pavo cristatus.

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