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PubMed1997

Feather pecking in domestic chicks: its relation to dustbathing and foraging

Feather pecking is a serious problem in poultry housing, as it may lead to feather damage, injuries and even mortality. We tested predictions of the two prevalent hypotheses claiming that feather pecking is related to dustbathing and foraging, respectively. Forty-two groups of 30 laying hen chicks, Gallus gallus domesticuswere reared in pens with a slatted floor. Access to sand as a dustbathing substrate and straw as a foraging substrate was varied between groups. The rate of feather pecking was measured in early development up to week 7. The provision of a sand area did not prevent the chicks from developing high rates of feather pecking that caused injuries. Chicks that had access to sand from day 10 showed higher rates of feather pecking than chicks that had access to sand from day 1. The provision of straw to chicks that had developed high rates of feather pecking led to a decrease in this behaviour. Chicks that could use both sand and straw from day 1 on did not show high rates of feather pecking, and no injuries were observed in these groups. There was no significant difference in dustbathing activity between housing conditions characterized by high or low rates of feather pecking. On the other hand, foraging activity was inversely related to the rate of feather pecking, and the occurrence of feather pecking could be delayed from week 4 to week 7 by postponing procedures that led to changes in foraging behaviour. In conclusion, the results show that the presence of an appropriate substrate for dustbathing does not prevent domestic chicks from developing feather pecking. On the other hand, housing conditions that promote foraging behaviour are effective in reducing and preventing feather pecking.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Journal Article↗
PubMed2000

Metals in albatross feathers from midway atoll: influence of species, age, and nest location.

Female birds sequester some heavy metals in their eggs, which are then transferred to the developing embryo. Semiprecocial birds such as albatrosses are fully covered with down at hatching, but are dependent on their parents for food for many weeks. At hatching, levels of metals in the chick's down represent exposure from the female via egg, while levels in fully formed feathers at fledgling, several months later, represent mainly exposure from food provided by their parents. In this paper we examine the concentrations of "metals" (heavy metals, mercury, lead, cadmium, chromium, manganese, tin; and metalloids, arsenic and selenium), in the down and contour (body) feathers of half-grown young albatrosses, and contour feathers of one of their parents. We collected feathers from Laysan Diomedea immutabilis and black-footed Diomedea nigripes albatrosses from Midway Atoll in the central Pacific Ocean. We test the null hypotheses that there is no difference in metal levels as a function of species, age, feather type, and location on the island. Using linear regression we found significant models accounting for the variation in the concentrations of mercury, lead, cadmium, selenium, chromium, and manganese (but not arsenic or tin) as a function of feather type (all metals), collection location (all metals but lead), species (selenium only), and interactions between these factors. Most metals (except mercury, arsenic, and tin) were significantly higher in down than in the contour feathers of either chicks or adults. Comparing the two species, black-footed albatross chicks had higher levels of most elements (except arsenic) in their feathers and/or down. Black-footed adults had significantly higher levels of mercury and selenium. We also collected down and feathers from Laysan albatross chicks whose nests were close to buildings, including buildings with flaking lead paint and those that had been lead-abated. Lead levels in the down and feathers of chicks close to nonabated buildings were 10 times higher than for chicks from other locations. Conversely, levels of cadmium and tin were lower near the buildings. Near lead-abated buildings, lead levels decreased as a function of distance, indicating residual contamination on the soil. Our results indicate that black-footed albatross adults and chicks generally have higher levels of heavy metals in their feathers than Laysans. Chicks of both species have higher levels in their down than in their contour feathers, indicating potentially higher exposure during the early chick phase.

Animals↗
PubMed2002

Tissue levels of lead in experimentally exposed zebra finches (Taeniopygia guttata) with particular attention on the use of feathers as biomonitors.

We tested experimentally whether zebra finch feathers can be used as a biomonitor for lead pollution, and we examined whether lead exposure influences the accumulation of zinc into feathers. Two groups of eight adult male zebra finches were dosed with, respectively, 0 and 25 ppm lead as lead acetate in their drinking water. After 30 days, lead-treated zebra finches accumulated significantly higher lead concentrations in brain, fat, kidney, liver, muscle, testes, and regrown outer tail feathers than control individuals. Lead levels in regrown outer tail feathers were significantly higher than in original outer tail feathers in the exposed group. The concentration of lead in original (not regrown) fifth tail feathers at the end of the experiment was significantly higher than lead levels in the original outer tail feathers. Our results indicate that lead in regrown feathers originates both from internal deposition and external contamination through the excretion of the uropygial gland during preening. Lead levels in regrown feathers were significantly correlated with levels in liver, kidney, and muscle, suggesting that feathers can be used as a biomonitor for lead. We found that lead had an influence on the metabolism of zinc. Zinc concentrations in the regrown feathers were significantly lower in the lead-treated group although zinc levels in the liver did not differ significantly. Moreover, lead and zinc concentrations in the feathers were significantly negatively correlated.

Animals↗
PubMed2002

Dust-mite allergen removal from feathers by commercial processing.

BACKGROUND: Individuals with allergies or asthma have had a long-standing bias against the use of chicken, goose, and duck feather pillows, comforters, quilts, and mattresses. OBJECTIVE: We show that raw, unprocessed feathers contain dust-mite allergen that is removed by washing, and that feather pillows, whether covered or not, do not internally accumulate dust-mite allergen when used in mite-infested bedrooms over a 3-month period. METHODS: Feathers obtained from six companies as unprocessed feathers (n = 8 batches) and processed feathers (n = 16 batches) were analyzed for dust-mite (Der p 1 and Der f 1) using monoclonal antibody-based immunoenzyametric assays with appropriate internal controls. Five pairs of new feather pillows (one covered and one uncovered) were placed in five bedrooms with known dust-mite contamination for 90 days. The pillows were then assayed for mite content. RESULTS: Dust-mite allergen was detected in 7 of 8 unprocessed feather samples; combined Der p 1 and Der f 1 mean = 524 ng/g, range 152 to 1,850 ng/g, whereas all 17 manufacturer-processed feather samples contained no detectable dust-mite. Although 4 of 5 bedrooms contained significant dust-mite allergen (>2,000 ng or Der p 1 and f 1, range 2,500 to 10,300 ng/g), none of the 90-day feather pillows became contaminated by dust-mite allergen even in the absence of a pillow cover. CONCLUSIONS: Feathers washed using industrial methods do not contain detectable dust-mite allergen. Pillows manufactured with processed feathers, whether encased in a dust cover or not, do not become contaminated by dust-mite allergen after 90 days of use in environments containing significant dust-mite allergen contamination.

Animals↗
PubMed2004

Effect of dietary crude protein and lysine on feather growth in chicks to twenty-one days of age.

A study was conducted to evaluate feather development in male broiler chickens fed variable levels of dietary CP and lysine. Diets contained 170, 210, 250, or 290 g of CP/kg with 0.86, 1.22, 1.34, or 1.46% lysine, each being fed to 2 replicate groups of 4 chicks. Dietary CP per se had a significant effect on feather weight and feather nitrogen gain. Increasing dietary CP from 170 to 250 g of CP/kg of diet increased feather weight and feather nitrogen gain. No differences were found at higher dietary CP levels. Dietary lysine levels from 0.86 to 1.46% did not affect feather weight, feather nitrogen gain, or feather:body weight in male chicks to 21 d. However, feather weight and feather nitrogen gain decreased as lysine increased in diets with 170 and 210 g of CP but not with 250 or 290 g of CP/kg. Percentage of total feather nitrogen was also influenced by the level of dietary lysine in diets containing 210 and 250 g of CP/kg. Feather development was more influenced by dietary CP per se than by levels of lysine.

Animals↗
PubMed1998

Allergy to feathers.

Skin prick test reactivity to commercial and self-made feather-allergen extracts was examined in 269 consecutive adult patients with suspected allergic cutaneous or respiratory symptoms who had been referred to a university clinic. Some 177 subjects reacted to any inhalant allergen. Twenty-four (9% of the whole group and 14% of those positive to any inhalant allergen) reacted to commercial feather extracts from ALK (Hørsholm, Denmark), and 51 to any of the seven feather extracts used. Feather-mix RAST (Pharmacia, Sweden) was positive in three cases only. Skin prick test or CAP-RAST or both to house-dust mite were positive in 16 of those 24 subjects positive to the commercial feather extracts, but in only 23 of the 150 other atopic subjects (P < 0.001). A nasal challenge with a feather extract was made in 20 cases, always with negative result. In immunospot studies, concomitant allergy to feather-allergen extracts and house-dust mite could be demonstrated. Mite allergens in feather extracts were verified in RAST-inhibition studies. A clinically significant feather allergy was found in one patient only. The results suggest that true feather allergy is very rare, and most of the positive reactions seen in skin prick tests to feather extracts are probably caused by mite allergens present in feathers.

Adolescent↗
PubMedDate not supplied

High virus titer in feather pulp of chickens infected with subgroup J avian leukosis virus.

Subgroup J avian leukosis viruses (ALVs), which are a recombinant virus between exogenous and endogenous ALVs, can spread by either vertical or horizontal transmission. Exogenous and endogenous ALVs can be detected in feather pulp. In this study, virus titers in feather pulp of chickens infected with subgroup J ALV were compared with those of plasma and cloacal swab. All of the broiler chickens inoculated with subgroup J ALV at 1 day old were positive for virus from feather pulp during the experimental period of between 2 wk and 8 wk of age. Virus titers in feather pulp of some broiler chickens infected with subgroup J ALV were very high, ranging from 10(7) to 10(8) infective units per 0.2 ml. Virus titers in feather pulp were usually the highest among the samples of plasma, cloacal swab, and feather pulp tested. In another experiment in which layer chickens were inoculated with subgroup J ALV at 1 day old, virus was detected in feather pulp from 2 wk until 18 wk of age, and virus persisted longer in feather pulp than in plasma. Almost all of the layer chickens tested were positive for virus by polymerase chain reaction (PCR) with DNA extracted from feather pulp samples at 2, 4, and 10 wk of age, and the PCR from feather pulp was more sensitive than virus isolation from plasma, cloacal swab, and feather pulp. All above results indicate that samples of feather pulp can be useful for virus isolation and PCR to confirm subgroup J ALV infection.

Animals↗
PubMed2003

Avian skin development and the evolutionary origin of feathers.

The discovery of several dinosaurs with filamentous integumentary appendages of different morphologies has stimulated models for the evolutionary origin of feathers. In order to understand these models, knowledge of the development of the avian integument must be put into an evolutionary context. Thus, we present a review of avian scale and feather development, which summarizes the morphogenetic events involved, as well as the expression of the beta (beta) keratin multigene family that characterizes the epidermal appendages of reptiles and birds. First we review information on the evolution of the ectodermal epidermis and its beta (beta) keratins. Then we examine the morphogenesis of scutate scales and feathers including studies in which the extraembryonic ectoderm of the chorion is used to examine dermal induction. We also present studies on the scaleless (sc) mutant, and, because of the recent discovery of "four-winged" dinosaurs, we review earlier studies of a chicken strain, Silkie, that expresses ptilopody (pti), "feathered feet." We conclude that the ability of the ectodermal epidermis to generate discrete cell populations capable of forming functional structural elements consisting of specific members of the beta keratin multigene family was a plesiomorphic feature of the archosaurian ancestor of crocodilians and birds. Evidence suggests that the discrete epidermal lineages that make up the embryonic feather filament of extant birds are homologous with similar embryonic lineages of the developing scutate scales of birds and the scales of alligators. We believe that the early expression of conserved signaling modules in the embryonic skin of the avian ancestor led to the early morphogenesis of the embryonic feather filament, with its periderm, sheath, and barb ridge lineages forming the first protofeather. Invagination of the epidermis of the protofeather led to formation of the follicle providing for feather renewal and diversification. The observations that scale formation in birds involves an inhibition of feather formation coupled with observations on the feathered feet of the scaleless (High-line) and Silkie strains support the view that the ancestor of modern birds may have had feathered hind limbs similar to those recently discovered in nonavian dromaeosaurids. And finally, our recent observation on the bristles of the wild turkey beard raises the possibility that similar integumentary appendages may have adorned nonavian dinosaurs, and thus all filamentous integumentary appendages may not be homologous to modern feathers.

Animals↗
PubMed1999

The role of long range, local and direct signalling molecules during chick feather bud development involving the BMPs, follistatin and the Eph receptor tyrosine kinase Eph-A4.

The development of the feather buds during avian embryogenesis is a classic example of a spacing pattern. The regular arrangement of feather buds is achieved by a process of lateral inhibition whereby one developing feather bud prevents the formation of similar buds in the immediate vicinity. Lateral inhibition during feather formation implicates a role of long range signalling during this process. Recent work has shown that BMPs are able to enforce lateral inhibition during feather bud formation. However these results do not explain how the feather bud escapes the inhibition itself. We show that this could be achieved by the expression of the BMP antagonist, Follistatin. Furthermore we show that local application of Follistatin leads to the development of ectopic feather buds. We suggest that Follistatin locally antagonises the action of the BMPs and so permits the cellular changes associated with feather placode formation. We also provide evidence for the role of short range signalling during feather formation. We have correlated changes in cellular morphology in feather placodes with the expression of the gene Eph-A4 which encodes a receptor tyrosine kinase that requires direct cell-cell contact for activation. We show that the expression of this gene precedes cellular reorganisation required for feather bud formation.

Animals↗
PubMed2001

Branched integumental structures in Sinornithosaurus and the origin of feathers.

The evolutionary origin of feathers has long been obscured because no morphological antecedents were known to the earliest, structurally modern feathers of Archaeopteryx. It has been proposed that the filamentous integumental appendages on several theropod dinosaurs are primitive feathers; but the homology between these filamentous structures and feathers has been disputed, and two taxa with true feathers (Caudipteryx and Protarchaeopteryx) have been proposed to be flightless birds. Confirmation of the theropod origin of feathers requires documentation of unambiguously feather-like structures in a clearly non-avian theropod. Here we describe our observations of the filamentous integumental appendages of the basal dromaeosaurid dinosaur Sinornithosaurus millenii, which indicate that they are compound structures composed of multiple filaments. Furthermore, these appendages exhibit two types of branching structure that are unique to avian feathers: filaments joined in a basal tuft, and filaments joined at their bases in series along a central filament. Combined with the independent phylogenetic evidence supporting the theropod ancestry of birds, these observations strongly corroborate the hypothesis that the integumental appendages of Sinornithosaurus are homologous with avian feathers. The plesiomorphic feathers of Sinornithosaurus also conform to the predictions of an independent, developmental model of the evolutionary origin of feathers.

Animals↗
PubMed2002

The morphogenesis of feathers.

Feathers are highly ordered, hierarchical branched structures that confer birds with the ability of flight. Discoveries of fossilized dinosaurs in China bearing 'feather-like' structures have prompted interest in the origin and evolution of feathers. However, there is uncertainty about whether the irregularly branched integumentary fibres on dinosaurs such as Sinornithosaurus are truly feathers, and whether an integumentary appendage with a major central shaft and notched edges is a non-avian feather or a proto-feather. Here, we use a developmental approach to analyse molecular mechanisms in feather-branching morphogenesis. We have used the replication-competent avian sarcoma retrovirus to deliver exogenous genes to regenerating flight feather follicles of chickens. We show that the antagonistic balance between noggin and bone morphogenetic protein 4 (BMP4) has a critical role in feather branching, with BMP4 promoting rachis formation and barb fusion, and noggin enhancing rachis and barb branching. Furthermore, we show that sonic hedgehog (Shh) is essential for inducing apoptosis of the marginal plate epithelia, which results in spaces between barbs. Our analyses identify the molecular pathways underlying the topological transformation of feathers from cylindrical epithelia to the hierarchical branched structures, and provide insights on the possible developmental mechanisms in the evolution of feather forms.

Animals↗
PubMed2005

Feathers as a nondestructive biomonitor for persistent organic pollutants.

Keratinous tissues of mammals and humans, such as hair, have been used to determine the exposure to polychlorinated biphenyls (PCBs) and organochlorine pesticides. In the present study, we investigated the accumulation of persistent organic pollutants (POPs; PCBs, p,p'-DDT, p,p'-dichlorodiphenyldichloroethane [DDD], p,p'-dichlorodiphenyldichloroethylene [DDE], hexachlorobenzene [HCB], oxychlordane, trans-nonachlor, polybrominated diphenyl ethers, and polybrominated biphenyls [PBBs]) in feathers of the great tit (Parus major). The accumulation of POPs in feathers and fat samples of 27 adult great tits collected in April 2000 and December 2002 was compared with regard to possible temporal and spatial differences. Polybrominated diphenyl ethers, PBBs, trans-nonachlor, and HCB could not be quantified in feathers. Most PCB congeners and DDTs (p,p'-DDE, p,p'-DDD, and p,p'-DDT) could be determined in feathers, although concentrations in feathers were markedly lower (sigmaPCB concentration range, 28.2-87.1 ng/g) than concentrations in fat (sigmaPCB concentration range, 1244-10074 ng/g). Feathers had relatively higher levels of low-chlorinated PCBs (tetra- and pentachlorinated biphenyls) and p,p'-DDD compared to levels in fat, presumably reflecting levels in blood. Persistent organic pollutant concentrations did not increase with the age of the feather, suggesting that exogenous or aerial depositions of POPs onto the feather surface had no, or only minimal, influence on levels in feathers. For almost all compounds studied, POPs in feathers and fat were significantly positively correlated in samples collected during the breeding season but not in samples collected during the winter. This temporal difference may have been caused by seasonal changes in lipid reserves. Although further research is required, feathers appear to be a promising new, nondestructive biomonitor for PCBs and DDTs in avian wildlife.

Animals↗
PubMed1998

Effect of a mixture of feather and blood meals on lactational performance of dairy cows.

An experiment was conducted over 18 wk of lactation to determine the effect of supplemental feather and blood meals (85:15, wt/wt, dry matter basis) fed at two dietary concentrations of crude protein (CP) on dry matter intake and milk protein production. Forty-eight Holstein cows were grouped by parity and assigned randomly at 3 wk postpartum to one of four diets following a 2-wk covariate period. Diets consisted of 50% alfalfa silage and 1) no feather or blood meals, 17.6% CP, and 5.1% ruminally undegradable protein (RUP); 2) 4% mixture of feather and blood meals, 17.6% CP, and 6.3% RUP; 3) no feather or blood meals, 19.6% CP, and 6.3% RUP; and 4) 4% mixture of feather and blood meals, 19.6% CP, and 6.9% RUP. According to the National Research Council, diet 1 was deficient in RUP, diets 2 and 3 were adequate in RUP, and diet 4 contained excessive CP and RUP. Intakes of dry matter and CP were depressed by 11% for cows fed the 19.6% CP diet supplemented with feather and blood meals. For cows fed the 17.6% CP diet, the supplementation of feather and blood meals increased RUP intake, but the supplementation of feather and blood meals to the 19.6% CP diet had no effect on RUP intake. Supplemental feather and blood meals increased the production of milk protein and 3.5% solids-corrected milk by cows fed the 17.6% CP diet. Diets 2, 3, and 4 resulted in similar efficiencies of solids-corrected milk production, but the efficiency of milk protein production specifically was increased by the supplementation of feather and blood meals to the 17.6% CP diet only. Results of this experiment indicate that a mixture of feather and blood meals improves the production of milk protein when supplemented to a diet that meets, but does not greatly exceed, the requirements established by the National Research Council for RUP and that contains alfalfa as the sole forage.

Animal Feed↗
PubMed1997

Feather mites are potentially an important source of allergens for pigeon and budgerigar keepers.

BACKGROUND: Previous studies on allergy to feathers have not addressed whether organisms living on feathers (mites, lice, moulds) are a source of allergens. OBJECTIVE: To investigate whether feather mites produced allergens of clinical relevance to bird keepers. METHODS: We examined serum IgE responses of 96 pigeon breeders to an extract of feather mites from pigeons (predominantly Diplaegidia columbae), using Western blotting, specific IgE assay using AlaSTAT EIA and RAST inhibition. RESULTS: Feather mites are a major source of soluble proteins derived from feathers, accounting for up to 10% of the total weight of the feather. Forty-three sera had a negative score (0) for anti-feather mite IgE, 27 were weakly positive (1-2) and 26 had strongly positive scores (3-4). Fewer pigeon breeders with scores > or = 3 were asymptomatic than those with negative scores (12 versus 40%), more had late onset symptoms (with or without early onset symptoms: 77% versus 44%) and had IgE antibody against house dust mite (89% versus 23%). Western blotting of eight sera against the extract of Diplaegidia columbae revealed 20 IgE-binding components ranging from 22 to 200 kDa. A high diversity of components was recognized by each serum: arithmetic mean 7 (range 2-14). RAST inhibition indicated feather mites had species-specific epitopes as well as ones that cross-reacted with Dermatophagoides pteronyssinus. CONCLUSION: Strongly-positive AlaSTAT scores to pigeon feather mite were associated with allergic symptoms of late onset in pigeon breeders. We conclude that feather mites are a major source of clinically-relevant allergens for pigeon breeders.

Allergens↗
PubMed1998

The effect of quality and availability of foraging materials on feather pecking in laying hen chicks.

Feather pecking resulting in feather damage, injuries and mortality causes severe welfare problems in laying hens. In the present study, we tested whether there is an inverse relationship between feather pecking and foraging behaviour (exploratory and manipulative behaviour away from the feeder). Forty-eight groups of 30 or 31 chicks, Gallus gallus domesticus, were reared in pens and provided with different types of foraging material. Feather pecking and foraging behaviour were quantified when the chicks were 4 and 5 weeks of age. In experiment 1, chicks with access to long-cut straw showed more foraging behaviour and less feather pecking than chicks that were provided with the same straw but in shredded form. On the other hand, there was no difference in foraging behaviour and feather pecking between chicks reared with access to long-cut straw and polystyrene blocks. In experiment 2, the importance of the form of the foraging material was confirmed. Chicks provided with polystyrene blocks performed more foraging behaviour and less feather pecking than chicks with access to polystyrene beads. The provision of an area with a layer of wood-shavings to promote scratching behaviour had no significant effect, however, on the incidence of feather pecking. In experiment 3, polystyrene blocks and beads were offered during the whole day or only in the morning. Both the quality and the availability of the foraging materials had a significant effect on foraging behaviour and a significant but opposite effect on feather pecking. Focal animal observations showed that the chicks performed different types of foraging behaviour at polystyrene blocks and beads. This suggests that not only the quantity but also the quality of foraging behaviour elicited by a given material may be important to prevent the development of feather pecking. Feather pecking should thus be considered as redirected foraging behaviour. Copyright 1998 The Association for the Study of Animal Behaviour. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2000

Is there social transmission of feather pecking in groups of laying hen chicks?

Feather pecking is an abnormal behaviour where laying hens peck the feathers of conspecifics, damaging the plumage or even injuring the skin. If it occurs in a flock, more and more birds show it within a short period of time. A possible mechanism is social transmission. Several studies have shown that laying hen chicks, Gallus gallus domesticus, are able to modify their own behaviour when observing the behaviour of other chicks, for example, when feeding and foraging. As there is good experimental evidence that feather pecking originates from foraging behaviour, we hypothesized that feather pecking could also be socially transmitted. To test this, we reared 16 groups of 30 chicks. After week 4, the birds were regrouped into 16 groups of 20 chicks into each of which we introduced either five chicks that showed high frequencies of feather pecking or, as controls, five chicks that had not developed feather pecking. We then determined the feather-pecking rate and the frequency of foraging, dustbathing, feeding, drinking, preening, moving, standing and resting of all birds in a group. Data from the introduced birds were analysed separately and excluded from the group data. Chicks in groups with introduced feather-pecking chicks had a significantly higher feather-pecking rate than chicks in the control groups. In addition, birds in groups with introduced feather peckers showed significantly lower foraging frequencies than those in the control groups, although the housing conditions were identical and there were no differences in either the number or the quality of the stimuli relevant to foraging behaviour. The study therefore suggests that feather pecking is socially transmitted in groups of laying hen chicks. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2002

Shh-Bmp2 signaling module and the evolutionary origin and diversification of feathers.

To examine the role of development in the origin of evolutionary novelties, we investigated the developmental mechanisms involved in the formation of a complex morphological novelty-branched feathers. We demonstrate that the anterior-posterior expression polarity of Sonic hedgehog (Shh) and Bone morphogenetic protein 2 (Bmp2) in the primordia of feathers, avian scales, and alligator scales is conserved and phylogenetically primitive to archosaurian integumentary appendages. In feather development, derived patterns of Shh-Bmp2 signaling are associated with the development of evolutionarily novel feather structures. Longitudinal Shh-Bmp2 expression domains in the marginal plate epithelium between barb ridges provide a prepattern of the barbs and rachis. Thus, control of Shh-Bmp2 signaling is a fundamental component of the mechanism determining feather form (i.e., plumulaceous vs. pennaceous structure). We show that Shh signaling is necessary for the formation and proper differentiation of a barb ridge and that it is mediated by Bmp signaling. BMP signaling is necessary and sufficient to negatively regulate Shh expression within forming feather germs and this epistatic relationship is conserved in scale morphogenesis. Ectopic SHH and BMP2 signaling leads to opposing effects on proliferation and differentiation within the feather germ, suggesting that the integrative signaling between Shh and Bmp2 is a means to regulate controlled growth and differentiation of forming skin appendages. We conclude that Shh and Bmp signaling is necessary for the formation of barb ridges in feathers and that Shh and Bmp2 signaling constitutes a functionally conserved developmental signaling module in archosaur epidermal appendage development. We propose a model in which branched feather form evolved by repeated, evolutionary re-utilization of a Shh-Bmp2 signaling module in new developmental contexts. Feather animation Quicktime movies can be viewed at http://fallon.anatomy.wisc.edu/feather.html.

Alligators and Crocodiles↗
PubMed1977

Abnormal morphogenesis of feather structures and pattern in the chick embryo integument. II. Histological description.

The development of skin and feathers in highly feathered scaleless mutants and normal Single Comb White Leghorn chick embryos was analyzed histologically. In addition, the growth of mutant feathers in chorioallantoic membrane culture is reported as a verification of several inferences made from observations of serially staged fixed specimens. The most striking feature of scaleless high line feather development is the widespread appearance of condensed or nearly condensed dermis. The discrete arrangement of normal placodes with underlying condensed dermis is replaced in the mutant by a heterogeneously shaped group of extremely large islands of columnar ("placodized") epithelium as long as 3,000 micron. The shape and extent of the condensed areas of dermis reflect the shape and extent of the overlying "placodized" epithelium. The polarity of the epidermis in normal feather germs, i.e., thicker epidermis on the posterior surface, is absent in mutant feather germs. This absence of epidermal polarity is reflected in the aberrant outgrowth of the mutant feather primordial. In the mutant, the basal cell layer of the epidermis invades the dermal core of the aberrant feather germs and may form barb vane ridges or feather sheaths. This process had no counterpart in the development of normal down feathers.

Animals↗