Agricultural Biotechnology Journal

Agricultural Biotechnology Journal

Morphological, histological, and gene expression profiling of the respiratory system in the Iraqi hoopoe (Upupa epops)

Document Type : Research Paper

Authors
Salim Salih Ali Al-Khakani 1
Ranin Saffaa Hamad 1
Ali Kadum Homady Al-Jebori 2
Ekhlas Abid Hamza Alalwany 1
Jafar Ghazi Abbas Al-Jebori 1
Mustafa Fadhil 1
Ahlam J. H. Al-Khamas 1
Osama Murtadha 1
Amna Imad Jawad 1
Mohammed Salah Hasan Simawy 1
Siraj M. Alkafagy 1
Sabreen M. Al-Janabi 1
Hawraa K. Judi 3
1 Department of Anatomy and Histology, College of Veterinary Medicine, Al-Qasim Green University, Babylon, 51013, Iraq
2 Department of Animal Production, Sumer University, College of Agriculture, Babylon 51013, Iraq
3 Department of Medical Physics, Hilla University College, Babylon, Iraq
10.22103/jab.2026.27563.1962
Abstract
Objective
Studies have shown that the anatomical and functional organization of the avian respiratory system is highly specialized. However, in the hoopoe (Upupa epops), the integrated morphological, histological, and molecular features of the respiratory system have not yet been fully and clearly studied and reported. The aim of this study was to characterize the respiratory system of the hoopoe (Upupa epops) using an integrated morphological, histological, and molecular approach. The molecular analysis focused on genes involved in oxygen sensing, vascular signaling, and inflammation.
Materials and methods
Gross morphometry, histological analysis with hematoxylin and eosin and Masson's trichrome staining, and reverse transcription quantitative polymerase chain reaction (RT-qPCR) were used to study eight adult hoopoes (Upupa epops). Gene expression analysis was performed for hypoxia-inducible factor 1-alpha (HIF1A), vascular endothelial growth factor A (VEGFA), and tumor necrosis factor (TNF). The reference gene was ACTB. Appropriate paired statistical tests were used to assess morphometric measurements and gene expression levels. Correlation analyses were applied to study associations between molecular and structural variables.
Results
Tracheal diameter decreased significantly from cranial to caudal with a strong effect (p<0.001). The thickness of the left and right lungs was similar (p>0.05). Histological examination revealed ciliated pseudostratified epithelium and goblet cells in the trachea. The submucosa contained seromucous glands and was supported by hyaline cartilage. The lungs exhibited parabronchi, atria, infundibula, and a dense network of air capillaries. Hypoxia-inducible factor 1-alpha levels were higher in the lung compared to the trachea (p<0.05; fold-change >1.5). Vascular Endothelial Growth Factor A levels also increased in the lung (p<0.05; fold-change >1.5). Tumor Necrosis Factor (TNF (levels remained low and did not show a tissue difference (p>0.05). HIF1A and VEGFA levels were positively correlated across samples (r>0.6, p<0.05). Actin cytoskeleton beta (ACTB) expression was stable across the analyzed tissues. These molecular findings were consistent with the dense capillary network observed histologically.
Conclusion
The higher HIF1A transcript abundance observed in lung tissue may indicate enhanced activation of oxygen-responsive pathways; however, because HIF-1α protein levels and direct tissue oxygenation were not measured, these findings should not be interpreted as direct evidence of tissue hypoxia. This multi-level approach validates the use of combined morpho-histological and RT-qPCR analysis to characterize avian respiratory health and adaptation.
Keywords
air capillaries
hoopoe
lung
RT-qPCR
trachea
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Agricultural Biotechnology Journal
Volume 18, Issue 4
Summer 2026
Pages 593-614