Early development of gonads in Muscovy duck embryos

Characteristics of gonadal development were investigated in Muscovy duck embryos at various embryonic ages. Hematoxylin-Eosin and periodic acid-Schiff staining were used to identify primordial germ cells, oogonia and sustentacular cells. Gene specific primers were designed based on conserved regions of duck antimullerian hormone (AMH), oestrogen receptor-α (ESR-α), doublesex and Mab-3 related transcription factor-1(DMRT1) and W chromosome protein kinase C inhibitor/interacting gene (WPKCI). Quantitative real-time polymerase chain reaction was used to characterise gene expression during gonad development in Muscovy duck embryos. Histology indicated that ovarian and testicular cells of Muscovy duck embryos developed on d 9 and 10. Immunohistochemistry showed that mouse vasa homologue-positive cells as well as Glial cell line-derived neurotrophic factor-positive cells increased significantly more in females than in males between d 9 and 10. AMH and ESR-α expression increased significantly during early development. DMRT1 acts prior to and during testis differentiation whereas WPKCI was expressed actively in the female Muscovy duck embryo before the onset of gonadal differentiation. Gonad development in Muscovy duck embryo was associated with several genes that were expressed before morphological features appear and were gender specific.