Characterizing early embryonic development of Brown Tsaiya Ducks (Anas platyrhynchos) in comparison with Taiwan Country Chicken (Gallus gallus domestics).

Chompunut Lumsangkul,Hsin-I Chiang,Yang-Kwang Fan,Jyh-Cherng Ju,Shen-Chang Chang,Arda Yildirim

doi:10.1371/journal.pone.0196973

Abstract

Avian embryos are among the most convenient and the primary representatives for the study of classical embryology. It is well-known that the hatching time of duck embryos is approximately one week longer than that of chicken embryos. However, the key features associated with the slower embryonic development in ducks have not been adequately described. This study aimed to characterize the pattern and the speed of early embryogenesis in Brown Tsaiya Ducks (BTD) compared with those in Taiwan Country Chicken (TCC) by using growth parameters including embryonic crown-tail length (ECTL), primitive streak formation, somitogenesis, and other development-related parameters, during the first 72 h of incubation. Three hundred and sixty eggs from BTD and TCC, respectively, were incubated at 37.2°C, and were then dissected hourly to evaluate their developmental stages. We found that morphological changes of TCC embryos shared a major similarity with that of the Hamburger and Hamilton staging system during early chick embryogenesis. The initial primitive streak in TCC emerged between 6 and 7 h post-incubation, but its emergence was delayed until 10 to 13 h post-incubation in BTD. Similarly, the limb primordia (wing and limb buds) were observed at 51 h post-incubation in TCC embryos compared to 64 h post-incubation in BTD embryos. The allantois first appeared around 65 to 68 h in TCC embryos, but it was not observed in BTD embryos. At the 72 h post-incubation, 40 somites were clearly formed in TCC embryos while only 32 somites in BTD embryos. Overall, the BTD embryos developed approximately 16 h slower than the chicken embryo during the first 72 h of development. To our best knowledge, this is the first study to describe two distinct developmental time courses between TCC and BTD, which would facilitate future embryogenesis-related studies of the two important avian species in Taiwan.

Highlights

Advantages of using avian embryos for the study of embryology lie in its ease of availability, manipulation and observation, as well as the relatively low cost of the eggs
We found that formation of the primitive streak in Taiwan Country Chicken (TCC) embryos was approximately one stage earlier than that of Brown Tsaiya Ducks (BTD) embryos
The length of primitive streak was fully extended around 18 h post-incubation in TCC and Hamburger and Hamilton (HH) embryos, but the time for reaching its full length was delayed until 25 h post-incubation in BTD embryos

Summary

Introduction

Advantages of using avian embryos for the study of embryology lie in its ease of availability, manipulation and observation, as well as the relatively low cost of the eggs. It has been popular to use avian eggs for the study of embryogenesis including organogenesis and morphogenesis, and the developmental stages are established in several avian species, such as chickens [1], quails [2], emus [3] and geese [4]. These species share some major features of early embryogenesis, they certainly possess species-specific characteristics of embryonic stages during the course of development. Nagai et al [3] have reported that emu embryos require approximately a 2- to 3-time longer incubation to reach the equivalent stages of chicken embryos

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