Pulmonary anatomy and a case of unilateral aplasia in a common snapping turtle (Chelydra serpentina): developmental perspectives on cryptodiran lungs

Abstract

The common snapping turtle (Chelydra serpentina) is a well studied and broadly distributed member of Testudines; however, very little is known concerning developmental anomalies and soft tissue pathologies of turtles and other reptiles. Here, we present an unusual case of unilateral pulmonary aplasia, asymmetrical carapacial kyphosis, and mild scoliosis in a live adult C. serpentina. The detailed three-dimensional (3D) anatomy of the respiratory system in both the pathological and normal adult C. serpentina, and a hatchling are visualized using computed tomography (CT), microCT, and 3D digital anatomical models. In the pathological turtle, the right lung consists of an extrapulmonary bronchus that terminates in a blind stump with no lung present. The left lung is hyperinflated relative to the normal adult, occupying the extra coelomic space facilitated by the unusual mid-carapacial kyphotic bulge. The bronchial tree of the left lung retains the overall bauplan of the normal specimens, with some minor downstream variation in the number of secondary airways. The primary difference between the internal pulmonary structure of the pathological individual and that of a normal adult is a marked increase in the surface area and density of the parenchymal tissue originating from the secondary airways, a 14.3% increase in the surface area to volume ratio. Despite this, the aplasia has not had an impact upon the ability of the turtle to survive; however, it did interfere with aquatic locomotion and buoyancy control under water. This turtle represents a striking example of a non-fatal congenital defect and compensatory visceral hypertrophy.

Computed tomographic and radiologic anatomy of the lower respiratory tract in the red-foot tortoise (Chelonoidis carbonaria)

“…The red-foot tortoise have lungs morphologically characterized as large multi-chamber structure, with many septa and rich in reticulated parenchyma, similar to that reported for other terrestrial Testudines (Christopher & Hernandez-Divers 2003, Duncker 2004. Schachner et al (2017) claimed that traditionally the morphology of the turtle lungs is multichambered. One of the most important clinical contributions of tomography examination is to describe the relationship of the respiratory system with other organs.…”

Parabronchial remodeling in chicks in response to embryonic hypoxia

“…Even ectothermic vertebrates, such as tadpoles, show gill hypertrophy, thinner skin (blood-water barrier) and an increased capillary bed in response to hypoxia (Burggren and Mwalukoma, 1983). Moreover, in a rare case of unilateral lung aplasia, an adult one-lunged snapping turtle (Chelydra serpentina) specimen showed a marked increase in compensatory pulmonary volume and surface area, as well as a larger surface-area-to-volume ratio in the remaining lung (Schachner et al, 2017).…”

Three-dimensional (3D) lung segmentation for diagnosis of COVID-19 and the communication of disease impact to the public

“…The 3D digital surface models (figures 1, 2A,C,E,G) were segmented by hand in the scientific visualisation programme Avizo V.7.1 (Thermo Fisher Scientific) following established methods for lungs in non-model organisms. [2][3][4] The utility of CT in the diagnosis of COVID-19 pneumonia has been a focus of recent radiologic literature with specific CT patterns of findings being well documented, including patchy and/or confluent, bandlike ground glass opacity or consolidation in a peripheral and mid-to-lower lung zone distribution. [5][6][7][8][9][10][11][12] Given diagnostic challenges with respect to false-negative results by RT-PCR, the gold standard for COVID-19 diagnostic screening, CT can be helpful in establishing this diagnosis.…”