Heterochrony and Early Left-Right Asymmetry in the Development of the Cardiorespiratory System of Snakes

Abstract

Snake lungs show a remarkable diversity of organ asymmetries. The right lung is always fully developed, while the left lung is either absent, vestigial, or well-developed (but smaller than the right). A ‘tracheal lung’ is present in some taxa. These asymmetries are reflected in the pulmonary arteries. Lung asymmetry is known to appear at early stages of development in Thamnophis radix and Natrix natrix. Unfortunately, there is no developmental data on snakes with a well-developed or absent left lung. We examine the adult and developmental morphology of the lung and pulmonary arteries in the snakes Python curtus breitensteini, Pantherophis guttata guttata, Elaphe obsoleta spiloides, Calloselasma rhodostoma and Causus rhombeatus using gross dissection, MicroCT scanning and 3D reconstruction. We find that the right and tracheal lung develop similarly in these species. By contrast, the left lung either: (1) fails to develop; (2) elongates more slowly and aborts early without (2a) or with (2b) subsequent development of faveoli; (3) or develops normally. A right pulmonary artery always develops, but the left develops only if the left lung develops. No pulmonary artery develops in relation to the tracheal lung. We conclude that heterochrony in lung bud development contributes to lung asymmetry in several snake taxa. Secondly, the development of the pulmonary arteries is asymmetric at early stages, possibly because the splanchnic plexus fails to develop when the left lung is reduced. Finally, some changes in the topography of the pulmonary arteries are consequent on ontogenetic displacement of the heart down the body. Our findings show that the left-right asymmetry in the cardiorespiratory system of snakes is expressed early in development and may become phenotypically expressed through heterochronic shifts in growth, and changes in axial relations of organs and vessels. We propose a step-wise model for reduction of the left lung during snake evolution.

Evaluation of X‐ray tomography contrast agents: A review of production, protocols, and biological applications

“…The diffusion rate of PTA and OsO 4 was relatively slower and the stains failed to infuse inside the samples. Cardiovascular development and left–right asymmetry in the cardiorespiratory system of snakes were investigated by van Soldt et al (). Various samples were treated with 1% PTA in 100% methanol varying between 1 and 4 days and then transferred to pure methanol.…”

Reptiles as a Model System to Study Heart Development

“…Morphologically, the atrioventricular junction of (noncrocodilian) reptiles resembles a mammal atrioventricular junction with a very large membranous septal defect and with very poorly developed parietal leaflets. In crocodilians, the atrioventricular valve apparatus resembles that of birds and monotreme mammals (Van Mierop and Kutsche 1985b;Jensen et al 2013a).…”

“…They will give rise to the parachute-like atrioventricular valve. Only in crocodilians, which have a full ventricular septum, will the lateral cushions give rise to significant parietal leaflets (Van Mierop and Kutsche 1985b;Cook et al 2017). In crocodilians, birds, and mammals, the left and right atrioventricular junction have a similar offset and they all develop a membranous septum (Greil 1903;Shaner 1962;Cook et al 2017).…”

Ekokardiografi Mode-Brightness Pada Ular Sanca

“…Ekokardiografi dapat diketahui struktur anatomi, fungsi, maupun diagnosis beberapa penyakit pada ular (Schilliger et al, 2005). Meskipun citra organ paru-paru dan jantung secara mikro-CT pada sanca bola telah dilakukan oleh van Soldt et al, (2015), akan tetapi publikasi tentang penggunaan teknologi ekokardiografi pada ular di Indonesia saat ini masih belum dilaporkan. Penelitian ini melaporkan pencitraan ekokardiografi, ukuran dan posisi organ jantung berdasarkan acuan sisik ventral pada tiga spesies sanca, yaitu sanca batik, sanca bodo, dan sanca bola secara transkutan.…”