Motor incoordination, intracranial fat bodies, and breeding strategy in Crested ducks (Anas platyrhynchos f.d.)

Effects of the Number of Crested Cushions in Runzhou White-Crested Ducks on Serum Biochemical Parameters

We investigated the effects of crest cushions in Runzhou white-crested (RWC) ducks. A total of 322 duck eggs were collected for incubation; 286 eggs were fertilized, and 235 RCW ducks were hatched. All the RWC ducks were weighed after 100 days and counted, and the volume of the crest cushion was measured. The number of crest cushions was positively correlated with the body weight, volume of the crest cushion, and distance from the mouth (p < 0.05). The serum Ca, Mg, Fe, Cu, Zn, and Se contents in the multiple-crest-cushion group were significantly higher (p < 0.05), as were the levels of triglycerides, immunoglobulin A, immunoglobulin G, immunoglobulin M, and immunoglobulin D (p < 0.01). The opposite results were seen for glycosylated low-density lipoprotein (p < 0.01). Propionic acid and acetic acid contents differed significantly between the two groups (p < 0.05), as did butyric acid content (p < 0.01), being higher in the multiple-crest-cushion group. Thus, an increase in the number of crest cushions coincided with a change in various serum biochemical indicators. The number of crest cushions might be involved in regulating various mechanisms of RWC ducks and might have an immunoregulatory effect.

Identification of Genes Associated with Crest Cushion Development in the Chinese Crested Duck

The crest trait is a specific and widely distributed phenotype in birds. However, the shape and function vary in different species of birds. To understand the mechanism of crest formation, the present study used RNA sequencing and weighted gene co-expression network analysis (WGCNA) to identify the crest-cushion-associated genes in the Chinese crested (CC) duck. As a result, 28, 40, 32, 33, and 126 differentially expressed genes (DEGs) were identified between CC and cherry valley (CV) ducks at the embryonic days (E)15, E22, E28, D7 (7 days old), and D42 stages, respectively. In addition, the results of WGCNA show that 3697 (turquoise module), 485 (green-yellow module), 687 (brown module), 205 (red module), and 1070 (yellow module) hub genes were identified in the E15, E22, E28, D7, and D42 stages, respectively. Based on the results of DEGs and WGCNA Venn analysis, three, two, zero, one, and seven genes were found to be associated with crest cushion formation at the E15, E22, E28, D7, and D42 stages, respectively. The expression of all the associated genes and some DEGs was verified by real-time quantitative polymerase chain reaction. In conclusion, this study provided an approach revealing the molecular mechanisms underlying the crested trait development.

Integrative analysis of histomorphology, transcriptome and whole genome resequencing identified DIO2 gene as a crucial gene for the protuberant knob located on forehead in geese

BACKGROUND

During domestication, remarkable changes in behavior, morphology, physiology and production performance have taken place in farm animals. As one of the most economically important poultry, goose owns a unique appearance characteristic called knob, which is located at the base of the upper bill. However, neither the histomorphology nor the genetic mechanism of the knob phenotype has been revealed in geese.

RESULTS

In the present study, integrated radiographic, histological, transcriptomic and genomic analyses revealed the histomorphological characteristics and genetic mechanism of goose knob. The knob skin was developed, and radiographic results demonstrated that the knob bone was obviously protuberant and pneumatized. Histologically, there were major differences in structures in both the knob skin and bone between geese owing knob (namely knob-geese) and those devoid of knob (namely non-knob geese). Through transcriptome analysis, 592 and 952 genes differentially expressed in knob skin and bone, and significantly enriched in PPAR and Calcium pathways in knob skin and bone, respectively, which revealed the molecular mechanisms of histomorphological differences of the knob between knob- and non-knob geese. Furthermore, integrated transcriptomic and genomic analysis contributed to the identification of 17 and 21 candidate genes associated with the knob formation in the skin and bone, respectively. Of them, DIO2 gene could play a pivotal role in determining the knob phenotype in geese. Because a non-synonymous mutation (c.642,923 G > A, P265L) changed DIO2 protein secondary structure in knob geese, and Sanger sequencing further showed that the AA genotype was identified in the population of knob geese, and was prevalent in a crossing population which was artificially selected for 10 generations.

CONCLUSIONS

This study was the first to uncover the knob histomorphological characteristics and genetic mechanism in geese, and DIO2 was identified as the crucial gene associated with the knob phenotype. These data not only expand and enrich our knowledge on the molecular mechanisms underlying the formation of head appendages in both mammalian and avian species, but also have important theoretical and practical significance for goose breeding.

The Effects of Domestication on the Brain and Behavior of the Chicken in the Light of Evolution

The avian class is characterized by particularly strong variability in their domesticated species. With more than 250 breeds and highly efficient commercial lines, domestic chickens represent the outcome of a really long period of artificial selection. One characteristic of domestication is the alterations in brain size and brain composition. The influence of domestication on brain morphology has been reviewed in the past, but mostly with a focus on mammals. Studies on avian species have seldom been taken into account. In this review, we would like to give an overview about the changes and variations in (brain) morphology and behavior in the domestic chicken, taking into consideration the constraints of evolutionary theory and the sense or nonsense of excessive artificial selection.

Selection for Divergent Reproductive Investment Affects Neuron Size and Foliation in the Cerebellum

The cerebellum has a highly conserved internal circuitry, but varies greatly in size and morphology within and across species. Despite this variation, the underlying volumetric changes among the layers of the cerebellar cortex or their association with Purkinje cell numbers and sizes is poorly understood. Here, we examine intraspecific scaling relationships and variation in the quantitative neuroanatomy of the cerebellum in Japanese quail (Coturnix japonica) selected for high or low reproductive investment. As predicted by the circuitry of the cerebellum, the volumes of the constituent layers of the cerebellar cortex were strongly and positively correlated with one another and with total cerebellar volume. The number of Purkinje cells also significantly and positively co-varied with total cerebellar volume and the molecular layer, but not the granule cell layer or white matter volumes. Purkinje cell size and cerebellar foliation did not significantly covary with any cerebellar measures, but differed significantly between the selection lines. Males and females from the high-investment lines had smaller Purkinje cells than males and females from the low-investment lines and males from the high-investment lines had less folded cerebella than quail from the low-investment lines. These results suggest that within species, the layers of the cerebellum increase in a coordinated fashion, but Purkinje cell size and cerebellar foliation do not increase proportionally with overall cerebellum size. In contrast, selection for differential reproductive investment affects Purkinje cell size and cerebellar foliation, but not other quantitative measures of cerebellar anatomy.

Whole genome re-sequencing of crested traits and expression analysis of key candidate genes in duck

The crested duck was a duck breed which features a topknot of feathers on the back of their head. In order to explain the reason of crest, we anatomy the head of some crested ducks. The anatomical structures showed that there was a fat body in the head and a hole in the skull. To determine the reason for the formation of the crest, we used whole genome re-sequencing to detect SNPs and InDels in three crested duck and three normal crested duck (without crest). There were 785,202 unique SNPs and 105,596 unique InDels include in crested duck. There were 14,591 SNPs containing genes and 13,784 InDels continuing genes were mapped on BGI_duck_1.0 by BWA 0.7.16a software. We use KEGG and GO to classification the SNP and InDel containing genes function. The PPI network of SNP containing genes and InDels containing genes was constructed by STRING. The result of PPI and KEGG analysis shown that the formation of crest might include feather development, fatty acid deposition, and skull hypoplasia. To determine the regulated of SNP containing genes and InDels containing genes, which related the different trait, of miRNA we used mirmap to predicted target miRNA of those genes. The miRNA-genes network constructed by Cytoscape. In conclusion, the formation of the crest was a complex process. The fatty acid metabolism block, feather growth and skull hypoplasia might lead crest formation. The tissue expression of four candidate genes showed that they were closely related to the formation of the trait, and could be used as important candidate genes to further elaborate the molecular mechanism of their function.

Unusual brain composition in Crested Ducks (Anas platyrhynchos f.d.)--including its effect on behavior and genetic transmission

Crested Ducks (CR) occasionally show intracranial fat bodies. Additionally, behavioral abnormalities such as motor incoordination can be observed. Here, it is shown that a behavioral test helps to identify CR that have a problematical fat body. The ducks were put on their backs, and the time required for them to stand up was measured. Ten CR exhibited suboptimal motor coordination. The appropriateness of this test has been proved in a special breeding program. To investigate the influence of fat bodies on brain composition, an allometrical comparison of 26 CR brains with those of three uncrested duck breeds was done. The fat bodies of CR varied from 0.3% to 41% of total brain volume, but two CR did not show a fat body. CR with motor incoordination show significantly larger fat bodies and require significantly more time in the test than "normal" CR. Total brain volume was significantly larger in CR, but brain volume minus fat body was significantly smaller compared to reference breeds. Cerebellum, apical hyperpallium, tegmentum and olfactory bulb are significantly reduced in CR. Obviously the behavioral deficits cannot be explained by the existence of a fat body, but they could be explained by functionally suboptimal cerebella and tegmenta. Fat body size seems to be a decisive factor. The relationship between fat body and reduced structures is discussed. By breeding with test-selected ducks the hatching rate increased and the number of ducklings with malformations or motor incoordination decreased.