Introduction

The species known as Coturnix japonica, or quail, belongs to the Phasianidae family (1). Japanese quail was successfully transferred from Japan to America, Europe, and the Middle East and Near East. The taming of Japanese quail began in Japan in the 11th decade (2 , 3). Quails are also often utilized as experimental animals. Due to these characteristics, rapid development, early sexual maturity, and low feed consumption, quails are commonly employed as in vivo models in physiological, pathological, toxicological, and anatomical research (4 , 5). The rise in quail meat and egg consumption in recent years has also bolstered the bird's economic aspect . Color of quail feathers is regarded as a race or hereditary characteristic. Mutations in the color are responsible for variations in the color of quail feathers (9) . White, brown, yellow, wild type (gray), and roux are the hues of the feathers (10) . Owing to their unique mode of transportation, birds acquired some physical characteristics that set them apart from other creatures (11) . The avian skeleton is adapted to active flying, in contrast to that of mammals. This special capacity is crucial to the preservation of bird species (12 , 13). The thin bony plates of the quail's skull are made of cartilaginous templates or connective tissue, much like in the skulls of all birds (14) . Birds have a third form of bone tissue termed the medullary bone in addition to the cortical and cancellous bones. The latter acts as a calcium store, which is crucial for females in relation to the development of their eggshells (15 , 16). Like other vertebrates, avian skulls are composed of two parts: the splanchnocranium and the neurocranium. The Occipital, sphenoidale, squamosum, parietale, frontale, paired ossa otica, unpaired os mesethmoidale, ectethmoidale, and lacrimale comprise the neurocranium in birds (17 , 18). Aerodynamic in form, the head tapers rostrally. The form and size of the bird's beak mostly determines the size and shape of its thin, typically tiny facial bones. The borders between the bones of the neurocranium are nearly undetectable since the bones of the neurocranium are entirely merged with one another (19) .

The shape of the beak dictates the conformation of the facial skeleton (20) . Because of the moveable connection with the skull, one unique trait is the capacity to lift the upper half of the beak. The os quadratum, the major component of the maxillopalatine apparatus, ensures this. The temporomandibular joint in mammals is analogous to it (21 , 22) . Particularly in tiny birds, the braincase is quite massive, and the orbits are very big, divided from one another by a narrow interorbital septum. Other vertebrates are unable to achieve the range of head mobility that the skull has because it is joined to the vertebral column by a single occipital condyle (23 , 24) . Similar to other birds, it can be difficult, if not completely impossible, to distinguish the sex of quails based only on the physical characteristics of their skulls. We think that the gender distinction in quails will be successfully achieved by the application of geometric morphometrics in skull dimensions (25) .

A frequently used method in the taxonomic categorization of animals is craniometrics, in this instance, morphometric data is used to establish interspecific differences (26) . From the perspective of intraspecific polymorphism and interspecific comparisons, the skull is an object of both geometric and linear morphometric, the study of species patterns and evolutionary processes is also made possible by geometric morphometries (27) . The main uses of feather colors have been in the following domains: sex selection; speciation and regional difference analysis; and diversity evolution (28) .

The majority of plumage color variations within and across species have a significant genetic component. According to many recent researches, quail plumage color changes are mostly caused by the interplay of certain gene mutations or combinations of mutations (29) . In an effort to connect the effects of feather color with growth characteristics in Japanese quails, also came to the conclusion that morphological traits specifically, feather color played a major role in both the identification process and the choice of quail varieties (30) . The taxonomic categorization of animals and the identification of gender differences have benefited from the widespread use of geometric morphometric techniques on a variety of breeds and species in recent years (31) . Therefore, the present study was conducted to determine the effect of plumage color patterns to identify the form differences between male and female quail individuals and to use geometric morphometries to assess the sex dimorphism of quail craniums.

Materials And Methods

The current experiment was done in the poultry farm of the animal production department, college of Agriculture - Kirkuk University, from (22/04/2022 to 22/07/2022), 120 unsexed chicks were used (White quail=40, Brown quail=40, and Gray quail=40), rearing on the cages, the diet and the water ad libitum when the flock reached 120 days of age 5 male, and female were chosen randomly to slaughter from each line. Following the slaughter all the heads were undergo dissection, muscles ,and skin and soft tissues were removed, the heads were gathered, boiled for a half hour ,and soaked in 5% hydrogen peroxide (H2O2) for 30 min to remove fatty tissue. Following these steps, the skulls were allowed to dry at room temperature in a well-ventilated area for one week (32) , and the characteristics of the skull were measured using a Caliper Vernier with an accuracy of 0.01 mm according to (33) landmarks. A general linear model (GLM) within the SPSS program was used to calculate the mean, standard error, and significance. Duncan multiple range test was used to test the differences between the means (34) .

Result

Table 1. Shows the effect of the genetic line of the Japanese quail on the size dimensions. There were significant differences in some dimensions, as the Pro. Sprameaticus of sequamosal bone was larger in the brown genetic line (18.876) mm compared to the white one, which was smaller. This is also the case with the Postorbital process (16.833) mm, as for the other dimensions, there were no significant differences between the genetic lines. Table 2 shows the effect of the genetic line of the Japanese quail on the sex of the bird. The table shows that there are no significant differences in the dimensions of size.

Table 3 shows the effect of the interaction between the genetic line and sex of the Japanese quail on size dimensions. There were highly significant differences in many dimensions, where the female white quail excelled over the rest of the birds in the Cerebellar prominentia trait (13.634) mm, and in the Exoccipital bone trait and Postorbital process, the male white quail excelled over the other birds (6.718, 15.731) mm respectively. The gray female quail also excelled in the Postorbital process, Dorsal middle point of frontonsal structure, and Middle point of frontonasal structure Basilar tuberculum of basioccipital bone (17.022, 4.941, 24.626) mm respectively, over the other of the birds. As for Paraoccipital process, white males, gray males and females outperformed other birds (15.481, 15.833, 15.654) respectively. As for the other of the characteristics, there was no significant effect among the studied interactions.

Discussion

In this experiment, the skull of quail birds was examined to determine and see the morphological differences between the male and female, in addition to the differentiation of dimension in some specific bones that related to the effect of the color. The study found that the male and female samples' form variances were quite close to one another. Meanwhile, the diversity between genetic lines was more evident. And that what was table 1 revealed. It shows the effect of the genetic line of the Japanese quail on the size dimensions. There were significant differences in some dimensions, as the Pro.

The Sprameaticus of sequamosal bone was larger in the brown genetic line (18.876) mm compared to the white one, which was smaller. This is also the case with the Postorbital process (16.833) mm, as for the other dimensions, there were no significant differences between the genetic lines. This result was in agreement with (35) , which shows the significant effect of the color pattern on the size and shape of the skull in avian. Table 3 shows the effect of the interaction between the genetic line and sex of the Japanese quail on size dimensions. There were highly significant differences in many dimensions, where the female white quail excelled over the rest of the birds in the Cerebellar prominentia trait (13.634) mm, and in the Exoccipital bone trait and Postorbital process, the male white quail excelled over the other birds (6.718, 15.731) mm respectively.

The gray female quail also excelled in the Postorbital process, Dorsal middle point of frontonsal structure, and Middle point of frontonasal structure Basilar tuberculum of basioccipital bone (17.022, 4.941, 24.626) mm respectively, over the other of the birds. As for Paraoccipital process, white males, gray males and females outperformed other birds (15.481, 15.833, 15.654) respectively. As for the other of the characteristics, there was no significant effect among the studied interactions. And that was in contrast with (36) , which shows no significant effect of sex and color on the weight and head size. Still, one may argue that sex discrimination within the same species benefits from the application of geometric form analysis. The disparities between boys and girls in longitudinal measures were discovered in a variety of skulls using classic morphometric techniques (37) . Males exhibited longer dimensions than females in the majority of these investigations. But geometric analysis allowed it to be understood in terms of shape. Information about geometric morphometry was gathered in order to calculate the sexual dimorphism and use it on other species such as dogs, goats, and sheep using geometric analysis (38) .

Conclusion

In this study, the effect of sexual dimorphism as well as the plumage color were studied by using the geometric morphometric method on the dimension of quail skull bones. Our study revealed a significant effect of the genetic lines of quail on the dimensions of the skull, especially in brown color line in some specific bones, meanwhile, no significant effect was shown between the sexes. Studies of geometric morphology will be very helpful in the classification of sexual dimorphism studies as well as using the major positive correlations among body weight and most body dimensions in quails and it gives high and low ranges and will bring a different perspective to traditional morphometric studies.

Conflicts of interest

The authors declare that there is no conflict of interest.

Ethical Clearance

This work is approved by The Research Ethical Committee.

References

1. Dey, P., Ray, S. D., Kochiganti, V. H. S., Pukazhenthi, B. S., Koepfli, K.-P.,& Singh, R. P. (2024). Mitogenomic Insights into the Evolution, Divergence Time, and Ancestral Ranges of Coturnix Quails. Genes, 15(6), 742. DOI; https://doi.org/10.3390/genes15060742.DOI
2. Çağlayan, T.,& Şeker, E. (2015). Dağ nanesinin (Mentha caucasica) japon bıldırcınlarının (Coturnix coturnix japonica) performans, bazı vücut ölçüleri ve canlı ağırlık arasındaki ilişkilerine etkisi. Eurasian Journal of Veterinary Sciences, 31(1): 33-42.
3. Lukanov, H.,& Pavlova, I. (2020). Domestication changes in Japanese quail (Coturnix japonica): A review. World's Poultry Science Journal, 76(4), 787–801. DOI: https://doi.org/10.1080/00439339.2020.1823303.DOI
4. Baer, J., Lansford, R.,& Cheng, K. (2015). Japanese quail as a laboratory animal model. In Laboratory animal medicine (pp. 1087–1108). Elsevier. DOI: https://doi.org/10.1016/b978-0-12-409527-4.00022-5.DOI
5. Redoy, M., Shuvo, A.,& Al-Mamun, M. (2017). A review on present status, problems and prospects of quail farming in Bangladesh. Bangladesh Journal of Animal Science, 46(2), 109–120. DOI: https://doi.org/10.3329/bjas.v46i2.34439.DOI
6. Tertychnaya, T., Manzhesov, V., Andrianov, E.,& Yakovleva, S. (2020). New aspects of application of microalgae Dunaliella Salina in the formula of enriched bread. Earth Environ. Sci. 422 012021. DOI: https://doi.org/10.1088/1755-1315/422/1/012021.DOI
7. Abd El-Hack, M. E., Majrashi, K. A., Fakiha, K. G., Roshdy, M., Kamal, M., Saleh, R. M., Khafaga, A. F., Othman, S. I., Rudayni, H. A., Allam, A. A., Moustafa, M., Tellez-Isaias, G.,& Alagawany, M. (2024). Effects of varying dietary microalgae levels on performance, egg quality, fertility, and blood biochemical parameters of laying Japanese quails (Coturnix coturnix Japonica). Poultry Science, 103(4), 103454. DOI: https://doi.org/10.1016/j.psj.2024.103454.DOI
8. Dalle Zotte, A.,& Cullere, M. (2024). Rabbit and quail: Little known but valuable meat sources. Czech Journal of Animal Science, 69(2), 39–47. DOI: https://doi.org/10.17221/165/2023-CJAS.DOI
9. Morris, K. M., Hindle, M. M., Boitard, S., Burt, D. W., Danner, A. F., Eory, L., Forrest, H. L., Gourichon, D., Gros, J.,& Hillier, L. W. (2020). The quail genome: Insights into social behaviour, seasonal biology and infectious disease response. BMC Biology, 18, 1–18. DOI: https://doi.org/10.1186/s12915-020-0743-4.DOI
10. Minvielle, F., Cecchi, T., Passamonti, P., Gourichon, D.,& Renieri, C. (2009). Plumage colour mutations and melanins in the feathers of the Japanese quail: A first comparison. Animal Genetics, 40(6), 971–974. DOI: https://doi.org/10.1111/j.1365-2052.2009.01929.x.DOI
11. Newton, Ian. (2007). The Migration Ecology of Birds. The Migration Ecology of Birds. DOI: http://doi.org/10.1016/B978-0-12-517367-4.X5000-1.DOI
12. Habib, M. B.,& Ruff, C. B. (2008). The effects of locomotion on the structural characteristics of avian limb bones. Zoological Journal of the Linnean Society, 153(3), 601–624.v DOI: https://doi.org/10.1111/j.1096-3642.2008.00402.x.DOI
13. Dumont, E. R. (2010). Bone density and the lightweight skeletons of birds. Proceedings of the Royal Society B: Biological Sciences, 277(1691), 2193–2198. DOI:  https://doi.org/10.1098/rspb.2010.0117.DOI
14. Thorogood, P. (1993). Differentiation and morphogenesis of cranial skeletal tissues. The Skull, 1, 112–152.
15. Tahara, R.,& Larsson, H. C. (2019). Development of the paratympanic pneumatic system of Japanese quail. Journal of Morphology, 280(10), 1492–1529. DOI: https://doi.org/10.1002/jmor.21045.DOI
16. Szara, T., Duro, S., Gündemir, O.,& Demircioğlu, İ. (2022). Sex determination in Japanese Quails (Coturnix japonica) using geometric morphometrics of the skull. Animals, 12(3), 302. DOI: https://doi.org/10.3390/ani12030302.DOI
17. Sridevi, P., Rajalakshmi, K., SivaKumar, M.,& Karthikeyan, A. (2020). Comparative gross anatomical studies on the neurocranium of Indian eagle owl, flamingo and common crow. Journal of Experimental Zoology India, 23(2). DOI: https://doi.org/10.18805/IJAR.B-4132.DOI
18. Duro, S., Ünal, B., Manuta, N., Çakar, B., Güzel, B. C.,& Korkmazcan, A. (2024). Morphometric study of neurocranium in different male chicken breeds raised in Turkey. Veterinaria, 73(1), 44–52. DOI: https://doi.org/10.51607/22331360.2024.73.1.44.DOI
19. Navalón, G., Bright, J. A., Marugán-Lobón, J.,& Rayfield, E. J. (2019). The evolutionary relationship among beak shape, mechanical advantage, and feeding ecology in modern birds. Evolution, 73(3), 422–435. DOI: https://doi.org/10.1111/evo.13655.DOI
20. Bright, J. A., Marugán-Lobón, J., Cobb, S. N.,& Rayfield, E. J. (2016). The shapes of bird beaks are highly controlled by nondietary factors. Proceedings of the National Academy of Sciences, 113(19), 5352–5357. DOI: https://doi.org/10.1073/pnas.1602683113.DOI
21. Onuk, B.,& Kabak, M. (2012). Comparative study of masticatory muscles in the goose (Anser anser domesticus) and the long-legged buzzard (Buteo rufinus). Ankara University Veterinary Fakultesi Dergisi, 59(1). DOI: https://doi.org/10.1501/Vetfak_0000002493.DOI
22. Güzel, B. C., Manuta, N., Ünal, B., Ruzhanova-Gospodinova, I. S., Duro, S., Gündemir, O.,& Szara, T. (2024). Size and shape of the neurocranium of laying chicken breeds. Poultry Science, 103(9), 104008. DOI: https://doi.org/10.1016/j.psj.2024.104008.DOI
23. Bhullar, B.-A. S., Hanson, M., Fabbri, M., Pritchard, A., Bever, G. S.,& Hoffman, E. (2016). How to make a bird skull: Major transitions in the evolution of the avian cranium, paedomorphosis, and the beak as a surrogate hand. Integrative and Comparative Biology, 56(3), 389–403. DOI: https://doi.org/10.1093/icb/icw069.DOI
24. Knoll, F.,& Kawabe, S. (2020). Avian palaeoneurology: Reflections on the eve of its 200th anniversary. Journal of Anatomy, 236(6), 965–979. DOI: https://doi.org/10.1111/joa.13160.DOI
25. Gündemir, O., Özkan, E., Dayan, M. O.,& Aydoğdu, S. (2020). Sexual analysis in Turkey (Meleagris gallopavo) neurocranium using geometricmorphometric methods. Turkish Journal of Veterinary& Animal Sciences, 44(3), 681–687. DOI: https://doi.org/10.3906/vet-1910-92.DOI
26. Kenyon-Flatt, B. (2020). Taxonomic efficacy of the macaque skeleton: A geometric morphometric analysis of the crania and Postcrania with regard to Ecogeography and behavior. ISBN: 9798672197296.
27. Boz, İ., Altundağ, Y., Szara, T., Hadziomerovic, N., Ince, N. G., Pazvant, G., Kahvecioğlu, O., Özkan, E., Manuta, N.,& Gundemir, O. (2023). Geometric morphometry in veterinary anatomy. Veterinaria, 72(1), 15–27. DOI: http://doi.org/10.51607/22331360.2023.72.1.15.DOI
28. Ng, C. S.,& Li, W.-H. (2018). Genetic and molecular basis of feather diversity in birds. Genome Biology and Evolution, 10(10), 2572–2586. DOI: http://doi.org/10.1093/gbe/evy180.DOI
29. Ghosh Roy, S., Bakhrat, A., Abdu, M., Afonso, S., Pereira, P., Carneiro, M.,& Abdu, U. (2024). Mutations in SLC45A2 lead to loss of melanin in parrot feathers. G3: Genes, Genomes, Genetics, 14(2), jkad254. DOI: http://doi.org/10.1093/g3journal/jkad254.DOI
30. Farajiarough, H., Rokouei, M., Maghsoudi, A.,& Ghazaghi, M. (2018). Comparative study of growth patterns in seven strains of Japanese quail using nonlinear regression modeling. Turkish Journal of Veterinary & Animal Sciences, 42(5), 441–451. DOI: http://doi.org/10.3906/vet-1801-13.DOI
31. Lansford, R.,& Cheng, K. M. (2024). The Japanese quail. The UFAW Handbook on the Care and Management of Laboratory and Other Research Animals, 762–786.
32. Kundu, S. K., Rocky, Z. H., Al Maruf, M. A., Chowdhory, A. T.,& Sayeed, A. (2023). Preparation of Quail (Coturnix coturnix) Skeleton to Promote the Teaching Facilities of Avian Anatomy Laboratory. International Journal of Veterinary and Animal Research, 6(3), 91–95. DOI: http://doi.org/10.5281/zenodo.10442793.DOI
33. Marugán-Lobón, J., Blanco Miranda, D., Chamero, B.,& Martín Abad, H. (2020). On the importance of examining the relationship between shape data and biologically meaningful variables. An example studying allometry with geometric morphometrics. Spanish Journal of Palaeontology, 28(2), 139–148. https://doi.org/10.7203/sjp.28.2.17848.DOI
34. Duncan, D. B. (1955). New multiple range test. Biometrics, 11(1), 1–42. DOI: http://dx.doi.org/10.2307/3001478.DOI
35. Zusi, R. L. (1993). Patterns of diversity in the avian skull. The Skull, 2, 391–437.
36. Moradian, H., Esmailizadeh, A. K., Sohrabi, S. S., Nasirifar, E., Askari, N., Mohammadabadi, M. R.,& Baghizadeh, A. (2014). Genetic analysis of an F 2 intercross between two strains of Japanese quail provided evidence for quantitative trait loci affecting carcass composition and internal organs. Molecular Biology Reports, 41, 4455–4462. DOI: http://doi.org/10.1007/s11033-014-3316-1.DOI
37. Demircioğlu, I., Demiraslan, Y., Gürbüz, I.,& Dayan, M. O. (2021). Geometric morphometric analysis of skull and mandible in Awassi ewe and ram. Kafkas Üniversitesi Veteriner Fakültesi Dergisi, 27(1). DOI: http://doi.org/10.9775/kvfd.2020.24714.DOI
38. Demiraslan, Y., Özgel, Ö., Gürbüz, İ.,& Kaştan, Ö. (2021). The mandibles of the Honamli and Hair goat (Capra hircus); a geometric morphometric study. Ankara Üniversitesi Veteriner Fakültesi Dergisi. DOI: https://doi.org/10.33988/auvfd.759964.DOI