Sex Of Birds Research Articles

Call for Your Life: Acoustic Structure and Age‐Sex Differences in Distress Calls of Red‐Necked Nightjars

ABSTRACTPredatory interactions result in strong selection pressures acting on multiple aspects of animal behaviour. Anti‐predator strategies are therefore common in most animals, typically signalling at various stages of a predation event. Many species of caprimulgids perform conspicuous anti‐predator displays, including stereotyped behaviours and vocal signals. Here, we described distress calls of red‐necked nightjars (Caprimulgus ruficollis), produced when birds are trapped and unable to escape during a predatory interaction. Distress calls are harsh, low‐frequency guttural vocalisations with irregular amplitude modulations. The age and sex of birds partially explained the acoustic variation observed, whereas size‐related morphological features were poor predictors of the acoustic structure. Age‐sex differences in distress calls may respond to physiological constraints associated with sexual dimorphism and/or developmental variation. Alternatively, directional selection associated with differential predation risk on each age‐sex class may have resulted in the observed differences in distress calls. The extremely deep voice and the harsh quality of distress calls fit the structure of aggressive signals and may resemble those produced by a larger animal. We propose that these calls serve as a last resort strategy to reduce post‐encounter risk of predation, either as a startling effect to facilitate escape or to attract other predators that could intimidate the captor.

Unveiling the critical role of androgen receptor signaling in avian sexual development

Gonadal hormone activities mediated by androgen and estrogen receptors, along with cell-autonomous mechanisms arising from the absence of sex-chromosome dosage compensation, are key factors in avian sexual development. In this study, we generate androgen receptor (AR) knockout chickens (AR−/−) to explore the role of androgen signaling in avian sexual development. Despite developing sex-typical gonads and gonadal hormone production, AR−/− males and females are infertile. While few somatic sex-specific traits persist (body size, spurs, and tail feathers), crucial sexual attributes such as comb, wattles and sexual behaviors remain underdeveloped in both sexes. Testosterone treatment of young AR−/− males fails to induce crow behavior, comb development, or regression of the bursa of Fabricius, which are testosterone-dependent phenotypes. These findings highlight the significance of androgen receptor mechanisms in fertility and sex-specific traits in chickens, challenging the concept of a default sex in birds and emphasizing the dominance of androgen signaling in avian sexual development.

Weather events influence survival and recruitment of Coereba flaveola (Bananaquit) in the Caribbean

Abstract The West Indies is considered a biodiversity hotspot and a priority for ecological conservation efforts. Understanding how environmental conditions influence survival of resident avifauna is an important information need given the predicted increases of drought and frequency and intensity of severe storms in the region. Throughout much of the Caribbean, Coereba flaveola (Bananaquit) are widespread and abundant, traits that may facilitate understanding their response to environmental changes in the region. We used a 10-yr capture–mark–recapture data set to examine C. flaveola survival, recruitment, population growth, and age structure in context of monthly and seasonal precipitation and temperatures, drought conditions, and occurrence and intensity of storm events. Our models suggested wing length, occurrence of storms, and drought all influenced survival. Both the incidence of storms and drier than average conditions in the preceding wet season (April–June) decreased survival. Sex of bird and net hours influenced capture probability, but weather influences on recruitment were equivocal. During non-storm years, mean population growth was stable at 1.019 (95% CI: 0.962, 1.098), but dropped to 0.843 (95% CI: 0.795, 0.846) in storm years. Increasing frequency of storms, such as back-to-back years, would likely push the growth rate lower. A protracted pattern of increased storm frequency, especially if coupled with a subsequent drought during the wet season, may lead to localized extirpations or strongly reduced populations.

Identifying the hidden parasitic intruders: Molecular insights into the health of common Myna

Birds are known to act as the parasite reservoir and can transmit them to other organisms through food chains. This study aims to report the molecular prevalence and phylogenetic evaluation of various blood borne pathogens (Toxoplasma gondii, Isospora spp., Plasmodium spp., Haemoproteus spp., Leucocytozoan spp. and Neospora caninum) in blood samples of common Myna (Acridotheres tristis: N = 80) collected from four region (Jhang, Khanewal, Multan and Muzaffargarh) in Punjab Pakistan. Effect of pathogens on the complete blood count of the host was also determined. Results revealed by 2/80 Myna (2.5 %) amplified ITS-1 gene of Toxoplasma (T.) gondii (confirmed by DNA sequencing) while 2/80 (2.5 %) birds amplified 18S rDNA gene and Isospora spp. Phylogenetic analysis of both pathogens showed that Pakistani isolates were clustered together and were closely related to isolates that were reported from worldwide countries.Risk factor analysis revealed that prevalence of both pathogens was not restricted to a particular sampling site or a particular bird sex (P > 0.05). T. gondii infected birds had elevated red cell distribution width while Isospora sp. infected birds had elevated % monocytes and platelet distribution width while decreased mean cell hemoglobin, mean corpuscular hemoglobin concentration and platelets hematocrit than their respective uninfected birds. In conclusion, we are reporting the presence of T. gondii and Isospora sp. among Pakistani common Myna that had disturbed the complete blood count parameters that may have affected their normal physiology.

PSVII-5 Heat shock protein 70 gene expression and association with morphometric and heat tolerance traits in three plumage colors of Noiler chicken exposed to acute heat stress

Abstract Heat stress is one of the most difficult climatic conditions chickens faces and is a direct result of climate change. It is important to research poultry thermotolerance because it may help find genetic lines resistant to heat stress. This study investigated the influence of plumage colors on heat shock protein 70 gene expression in Noiler chickens exposed to acute heat stress. Noiler is a dual-purpose breed developed for smallholder poultry production in Nigeria. A total of 150 birds of three plumage colors (black, brown and white) of mixed sexes were used for the experiment. The birds were raised in deep litter house separated into six groups of 25 birds each and fed with commercial broiler diets from 0-8 wk and broiler finisher diets from 8 to 12 wk old. The birds were shared into treatments in 3 x 2 x 2 factorial arrangements with 3 plumage colors (black, brown, white), two temperature regimens (Control/thermoneutral, Heat stress) and sex of birds (male, female). The heat stressed birds were exposed to 41oC for 8 h from 0600 h to 1400 h for 7 d while control group maintained a thermoneutral temperature range of 30 oC to 32 oC for the same period. At 13 wk old, two birds were selected per treatment, slaughtered and the spleen removed and stored in RNA later for heat shock protein (HSP) 70 gene expression. Data collected were analyzed with Microsoft excel code for fold expression of HSP70 gene while GLM procedure in SAS was used to determine difference in expression of gene. The relative expression of HSP70 brown plumage was greater, upregulated compared with black and white. White plumage birds in control/thermoneutral group were significantly greater in HSP70 expression than other plumage colors and heat stressed birds. Association of HSP70 delta threshold cycle (DCT) values with morphometric and heat tolerance traits were investigated (Figure 1). High negative correlations emerged between HSP70DCT expression and body weight (-0.65), body temperature (-0.73) with moderate positive correlation for rectal temperature (0.55) in black birds (Table 1). HSP70 DCT positively correlated with body weight (0.70), breast/leg circumferences but negatively with wing length, suggesting reduced surface area during heat stress and a supportive role in maintaining protein integrity (Figure 2). For white Noiler birds, HSP70DCT associated negatively with body weight (-0.94) and positively with rectal temperature during heat stress (Table 2). Thermoneutral birds were positively correlated with heat tolerance traits except temperature while heat stressed birds showed low positive correlation with respiratory and pulse rates and very low positive relationship with body and rectal temperatures (Table 4). Sex-based differences emerged, with potential compromise between HSP70-mediated growth/composition in males versus muscle maintenance in females, although leg length/circumference showed shared developmental regulation (Figure 3, Table 3). These findings highlight HSP70’s versatile roles in systemic heat tolerance mechanisms influenced by plumage color, temperature regime and sex.

Cross Sectional Study of Poultry Coccidiosis in Adele Poultry Farm, Eastern Hararghe, Oromia, Ethiopia

Objective: This study was to determine the number of chickens in intensively managed poultry farms and to assess the relationship between the number of chickens and risk factors in specific poultry farm. Methods: A cross-sectional study was conducted in Adele town between December 2014 and November 2015. The presence of oocysts in the fecal samples was examine by floatation methods and post-mortem examinations looked for intestinal lesions. Results: Out of the 262 chicken sample sources examined, 29 (11.01%) were positive for coccidian oocysts, and out of the 84 total Environmental sample source examined, 12 (14.4%) were positive for coccidian parasites. There were no statistically significant differences in prevalence across the sample type and source (p greater than 0.05). There were no changes in the prevalence of coccidiosis between the sexes of birds. Pless than 0.05 indicates a statistically significant difference between the age groups. Furthermore, a strong correlation was found between the sample times. The prevalence of coccidia was considerably higher in chicks than in adults (P less than 0.05). The environment had a greater prevalence of coccidiosis than faeces did. Of the environmental samples, the majority of coccidial infections are linked to management issues, and the prevalence of water and feed is higher than that of litter material. Conclusions: This study showed that coccidiosis is a significant disease affecting poultry in the studied area and that effective control measures must be developed to reduce the illness's impact.

Contents of Macro- and Microelements in Blood Serum and Breast Muscle of Turkey Subjected to Pre-Slaughter Transport for Various Distances.

In this study, the effect of pre-slaughter handling on the content of macro- and micronutrients in blood serum and in the breast muscle of turkeys was assessed. Four different variants of pre-slaughter handling were used in the research: no transport (N-T), transport for a distance of 100 km (T-100), transport for a distance of 200 km (T-200), and transport for a distance of 300 km (T-300). In each of them, 30 female and 30 male turkeys were used. Blood was collected from the birds before slaughter, and samples of the pectoral muscle were collected after slaughter. In the obtained biological material, the content of Mg, P, Ca, Fe, Na and K was analyzed. On the basis of the obtained research results, it can be concluded that the pre-slaughter handling negatively affects the content of macro- and microelements both in the blood serum and in the pectoral muscles of experimental turkeys. Additionally, differences due to the sex of birds were observed.

Comparison of three primer pairs for molecular sex determination in Eurasian pygmy owls (Glaucidium passerinum)

Bird sex determination is fundamental in various ecological and biological studies, although many avian species cannot be sexed visually due to their monomorphic and/or monochromatic appearance. Thus, reliable laboratory methods for sexing are a prerequisite. Most avian nestlings lack sex-related signs, including the Eurasian pygmy owl (Glaucidium passerinum). We performed laboratory sex determination analysis of this species using blood samples of 242 juveniles and nine adults. It relied on the qPCR of the specific intron from the chromo-helicase DNA-binding protein 1 gene. We tested three primer sets, the P2/P8, 2550F/2718R, and CHD1F/CHD1R, commonly used for bird laboratory sexing. The outcomes were displayed on an agarose gel electrophoresis and a plot from melt curve analysis, which had not been previously conducted in Eurasian pygmy owls. We found that only primer set CHD1F/CHD1R proved reliable, as the only one determined sex with one and two band/s and peak/s on the electrophoresis and the melt curve plot for males and females, respectively. The other two primer pairs failed and depicted one band/peak in all specimens regardless of their sex. Therefore, we recommend performing Eurasian pygmy owls’ laboratory sexing by qPCR with CHD1F/CHD1R primers only.

Evolution of bird sex chromosomes: a cytogenomic approach in Palaeognathae species

BackgroundDifferent patterns of sex chromosome differentiation are seen in Palaeognathae birds, a lineage that includes the ratites (Struthioniformes, Rheiformes, Apterygiformes, Casuariiformes, and the sister group Tinamiformes). While some Tinamiform species have well-differentiated W chromosomes, both Z and W of all the flightless ratites are still morphologically undifferentiated. Here, we conducted a comprehensive analysis of the ZW differentiation in birds using a combination of cytogenetic, genomic, and bioinformatic approaches. The whole set of satDNAs from the emu (Dromaius novaehollandiae) was described and characterized. Furthermore, we examined the in situ locations of these satDNAs alongside several microsatellite repeats and carried out Comparative Genomic Hybridizations in two related species: the greater rhea (Rhea americana) and the tataupa tinamou (Crypturellus tataupa).ResultsFrom the 24 satDNA families identified (which represent the greatest diversity of satDNAs ever uncovered in any bird species), only three of them were found to accumulate on the emu’s sex chromosomes, with no discernible accumulation observed on the W chromosome. The W chromosomes of both the greater rhea and the emu did not exhibit a significant buildup of either C-positive heterochromatin or repetitive DNAs, indicating their large undifferentiation both at morphological and molecular levels. In contrast, the tataupa tinamou has a highly differentiated W chromosome that accumulates several DNA repeats.ConclusionThe findings provide new information on the architecture of the avian genome and an inside look at the starting points of sex chromosome differentiation in birds.

Molecular sexing of birds using quantitative PCR (qPCR) of sex-linked genes and logistic regression models.

The ability to sex individuals is an important component of many behavioural and ecological investigations and provides information for demographic models used in conservation and species management. However, many birds are difficult to sex using morphological characters or traditional molecular sexing methods. In this study, we developed probabilistic models for sexing birds using quantitative PCR (qPCR) data. First, we quantified distributions of gene copy numbers at a set of six sex-linked genes, including the sex-determining gene DMRT1, for individuals across 17 species and seven orders of birds (n = 150). Using these data, we built predictive logistic models for sex identification and tested their performance with independent samples from 51 species and 13 orders (n = 209). Models using the two loci most highly correlated with sex had greater accuracy than models using the full set of sex-linked loci, across all taxonomic levels of analysis. Sex identification was highly accurate when individuals to be assigned were of species used in model building. Our analytical approach was widely applicable across diverse neognath bird lineages spanning millions of years of evolutionary divergence. Unlike previous methods, our probabilistic framework incorporates uncertainty around qPCR measurements as well as biological variation within species into decision-making rules. We anticipate that this method will be useful for sexing birds, including those of high conservation concern and/or subsistence value, that have proven difficult to sex using traditional approaches. Additionally, the general analytical framework presented in this paper may also be applicable to other organisms with sex chromosomes.

Evolution and expression patterns of the neo-sex chromosomes of the crested ibis

Bird sex chromosomes play a unique role in sex-determination, and affect the sexual morphology and behavior of bird species. Core waterbirds, a major clade of birds, share the common characteristics of being sexually monomorphic and having lower levels of inter-sexual conflict, yet their sex chromosome evolution remains poorly understood. Here, by we analyse of a chromosome-level assembly of a female crested ibis (Nipponia nippon), a typical core waterbird. We identify neo-sex chromosomes resulting from fusion of microchromosomes with ancient sex chromosomes. These fusion events likely occurred following the divergence of Threskiornithidae and Ardeidae. The neo-W chromosome of the crested ibis exhibits the characteristics of slow degradation, which is reflected in its retention of abundant gametologous genes. Neo-W chromosome genes display an apparent ovary-biased gene expression, which is largely driven by genes that are retained on the crested ibis W chromosome but lost in other bird species. These results provide new insights into the evolutionary history and expression patterns for the sex chromosomes of bird species.

Morphological Variations and Path Coefficient Analysis of Zoometric Traits of Local Chickens in Tolon District of Northern Ghana

The knowledge of morphometric measurements is paramount in domestic chicken production and marketing practices hence this research was undertaken to determine the morphological characteristics of domestic chicken in the Tolon District of Ghana. Birds reared under the traditional scavenging system, were randomly selected in four (Nyankpala, Tolon, Woribogu and Dondo) communities. Live body weight (BW) and thirteen morphometric traits namely, body length (BDL), chest circumference (CC), thigh circumference (TC), drumstick length (DL), shank length (SL), wing length (WGL), neck length (NL), head width (HDW), hip width (HPW), comb length (CL), head length (HDL), wattle length (WAL) and beak length (BKL) were measured. The data was subjected to general linear model, correlation and path coefficient analyses. The results revealed that, domestic chickens were generally smaller in sizes. The average values recorded were 0.99kg, 18.98cm, 20.60cm, 7.78cm, 11.78cm, 8.05cm, 16.17cm, 12.15cm, 2.34cm, 7.57cm, 3.39cm, 2.28cm, 1.70cm and 2.60cm for BW, BDL, CC, TC, DL, SL, WGL, NL, HDW, HPW, CL, HDL, WAL and BKL respectively. Location of birds significantly (P< 0.05) affected morphometric traits (BDL, CC, TC, SL, WGL, NL, HDW, CL, HPW, and WAL) of birds. Similarly, sex of birds had significant (P<0.05) effects on BDL, DL, SL, WGL, NL, HDW, CL, HDL, WAL and BKL whereas age had no significant (P>0.05) influence on any morphometric traits. The presence of crest affected (P<0.05) the variations in DL, SL, WAL and BKL. Also, presence of spur affected the variations (P<0.05) in BW, DL, NL, CL, HDL, WAL and BKL whiles comb type had no significant (P>0.05) effects on any morphometric trait. Correlation coefficients were generally low, with the highest (0.513) recorded between TC and CC. The highest direct path coefficient was obtained from CC (0.237), followed by BDL (0.156) and WAL (0.153). The findings of this work will be useful in characterization studies and breeding program for local domestic chickens.

Sex Identification of the Sun Conure (Aratinga solstitialis) Using Calamus Based on Polymerase Chain Reaction

Sex identification of Sun Conures (Aratinga solstitialis) is crucial for breeding and preservation, as well as increasing sun conure populations. These birds are sexually monomorphic. Therefore, Determination between male and female carried out by their morphology examination. The Polymerase Chain Reaction (PCR) method, utilizing molecular-based technology, was employed to determine the sex of Aratinga solstitialis in this study. The P2 and P8 primers were utilized in this method, which has been deemed suitable and accurate for sex identification through calamus samples. The research focused on two 28-month-old Aratinga solstitialis birds. Calamus samples were collected and subjected to PCR amplification using the extracted calamus. The resulting PCR products were then visualized using electrophoresis with a 1% agarose gel. In the electrophoresis photo, the presence of two bands indicated a female specimen, whereas a single band indicated a male specimen. The result of the gel electrophoresis research showed that both of the Aratinga solstitialis were male with one band of each bird on ranged from 300-400 base pairs. The result show that the Polymerase Chain Reaction method in terms for sex identification on monomorphic birds, especially Aratinga solstitialis birds is very effective to differentiate the sex of young birds and the adults.

Detection of infectious bursal disease virus (IBDV) antibodies in backyard poultry by using indirect enzyme linked immunosorbent assay

Infectious bursal disease virus (IBDV) causes infectious bursal disease in poultry and poses a major challenge to the poultry industry globally. This study aimed to measure seroprevalences and so detect exposure to IBDV in backyard poultry in the selected zone of Horro Guduru Wollega. A cross-sectional study was conducted from January 2021 to November 2022. Blood samples were collected for serum extraction from 384 backyard chickens in the Horro and Horro Bulluq districts. IBDV antibody detection was conducted using an indirect ELISA serological diagnostic test. Questionnaires assessed poultry owners? knowledge and health/hygiene management practices regarding the disease. The over all seroprevalence of IBDV was 14.84%. Significant variations in seroprevalence were seen based on district, bird age, bird sex, and flock size. Limited owner experience (just 1-3 years), disposing of carcasses in pits, and poor hygiene on the backyard premises were associated with higher IBDV seroprevalence. In conclusion, IBDV seroprevalence was linked to chicken management practices. Recommendations include improving poultry management among owners to control IBDV. The study indicates backyard poultry in the region have considerable IBDV exposure, and control should focus on improving management practices identified as high-risk, such as pit disposal of carcasses and poor hygiene.

Studies on pancreatic pathology of poultry in different diseases in relation to season, age, sex and varieties of birds

Studies on pancreatic pathology of poultry in different diseases in relation to season, age, sex and varieties of birds

Sex identification methods of birds: a review

Birds are mainly categorized as either monomorphic or dimorphic based on phenotypic characteristics. It is believed that nearly 60 % of the bird species are monomorphic and difficult to distinguish the sex during their early stages of life. It is important to identify the different sexes at a distance when birds are in the wild or in natural habitats, especially for bird lovers, biologists and conservationists to differentiate the behavioral patterns of birds. However, even aviculturists and experienced biologists have faced difficulties in identifying the different sexes of monomorphic birds at a distance. The key genes responsible for the sex differentiation of chickens are unclear due to their multiple gene expressions. Therefore, the sex determination of birds is more important in aviculture, poultry farming and in research fields. Hence, this review mainly focused on those invasive (laparoscopy), moderately invasive/ minimally invasive (Karyotyping and DNA-based techniques), and non-invasive methods (steroid sexing, vent sexing, morphometric observations, voicing) of sex identification of birds as much as possible and discussed the reliability of those techniques on the identification of the sex of birds. In light of the discussion, the accuracy of non-invasive techniques is very low and quite questionable. Despite the high accuracy, laparoscopy poses a life threat to the birds during the surgery due to the damage of internal organs while probing. DNA-based methods are concluded to be the best and most accurate techniques among almost all the techniques that require sophisticated laboratory facilities. Hence, the on-farm approach of Recombines polymerase amplification combined with a lateral-flow dipstick (RPA-LFD) can be suggested as one of the best alternatives to laboratory protocols that can be practiced without bringing down the accuracy of the sex determination of birds. Asian J. Med. Biol. Res. 2023, 9 (4), 134-144

Appropriate Primer Selection Improves Molecular Bird Sexing Accuracy

Birds sexing utilize the Polymerase Chain Reaction (PCR) technique is increasingly being used by researchers and breeders. The PCR technique has high sensitivity, but its success is influenced by the specificity of the DNA template with the oligo primer used. This study aimed to evaluate 5 types of PCR primers P2/P8, 2550F/2718R, CHD1F/CHD1R, 1237L/1272H, and CHD1LF/CHD1LR to determine the sex of Phasianidae, Anatidae, Muscicapidae, and Psittacidae families. This research was conducted by tested primers mentioned above to amplify the target gene chromodomain helicase DNA binding 1 (CHD1) on DNA samples of each pair of males and females from four bird families, respectively. The results indicated that CHD1LF/CHD1LR PCR primer gave the best results and was recommended to determine the sex of four families tested. Some of other primers tested in this study failed to amplify targeted gene correctly, it is important to use appropriate primer to increase bird sexing accuracy.

Individual body mass and sex of a frugivorous bird affect the quality of seed dispersal

AbstractFrugivorous animals play crucial roles dispersing seeds away from parental plants and influencing plant recruitment. Most studies focus on comparisons of seed dispersal services provided by distinct species of animals, but neglect how within‐species variation may affect dispersal. Individual traits, such as body mass and sex, are related to metabolic rates, gut load capacity, and transit times that potentially influence dispersal quantity and quality. Here, we aim at answering if individual traits (body mass and sex) of Pale‐breasted Thrushes (Turdus leucomelas) affect seed dispersal quality by testing the following hypotheses (a) individual traits influence seed retention time and germination, (b) seed retention time affects seed germination, and (c) seed passage through the gut enhances germination. We found that females retained seeds in the gut for longer periods than males. Gut passed and manually depulped seeds had similar germination success. However, heavier birds, irrespective of sex, had longer seed retention times and promoted higher germination. Our results indicate that intraspecific differences in morphological traits of frugivores are a source of variation in dispersal outputs and may help to explain complex patterns of seed dispersal. We highlight the importance of considering the quality of seed dispersal at an individual‐level, as well as at a species‐level, and reinforce that some individuals may contribute more to seed germination, and potentially recruitment, than others. Finally, a decrease in body masses of tropical birds in response to global warming may cascade to a decrease in seed dispersal quality.Abstract in Portuguese is available with online material.

Minimally Invasive Sampling Methods for Molecular Sexing of Wild and Companion Birds

Birds are highly social and must be paired in order to increase their welfare. Most bird species are monomorphic; therefore, molecular sexing helps provide appropriate welfare for birds. Moreover, early sex determination can be of great value for bird owners. The aim of this study was to demonstrate that sex identification in birds achieved using molecular methods and samples collected via minimally invasive methods is fast, efficient, and accurate. A total of 100 samples (29 paired samples of feathers and oral swabs and 14 tripled samples of feathers, oral swabs, and blood) from 43 birds were included in this study, as follows: wild birds (Falconiformes, Accipitriformes, landfowl—Galliformes, waterfowl—Anseriformes) and companion birds (Passeriformes, Psittaciformes—large-, medium-, and small-sized parrots). Amplification of CHD1-Z and CHD1-W genes was performed via conventional PCR. The results obtained from feathers were compared to those obtained from oral swabs and to those obtained from blood samples, where applicable. The obtained results show that all types of samples can be used for molecular sexing of all studied bird species. To the best of our knowledge, the present study reports, for the first time, molecular sex identification in Red Siskin (Carduelis cucullata) and Goldfinch (Carduelis carduelis major). For higher accuracy, our recommendation is to use minimally invasive samples (oral swabs and feathers) and to test both types of samples for each bird instead of blood samples.

Gene Expression Profiling Reveals Potential Players of Sex Determination and Asymmetrical Development in Chicken Embryo Gonads.

Despite the notable progress made in recent years, the understanding of the genetic control of gonadal sex differentiation and asymmetrical ovariogenesis in chicken during embryonic development remains incomplete. This study aimed to identify potential key genes and speculate about the mechanisms associated with ovary and testis development via an analysis of the results of PacBio and Illumina transcriptome sequencing of embryonic chicken gonads at the initiation of sexual differentiation (E4.5, E5.5, and E6.5). PacBio sequencing detected 328 and 233 significantly up-regulated transcript isoforms in females and males at E4.5, respectively. Illumina sequencing detected 95, 296 and 445 DEGs at E4.5, E5.5, and E6.5, respectively. Moreover, both sexes showed asymmetrical expression in gonads, and more DEGs were detected on the left side. There were 12 DEGs involved in cell proliferation shared between males and females in the left gonads. GO analysis suggested that coagulation pathways may be involved in the degradation of the right gonad in females and that blood oxygen transport pathways may be involved in preventing the degradation of the right gonad in males. These results provide a comprehensive expression profile of chicken embryo gonads at the initiation of sexual differentiation, which can serve as a theoretical basis for further understanding the mechanism of bird sex determination and its evolutionary process.