Adaptation to life in aeolian sand: how the sandfish lizard, Scincus scincus, prevents sand particles from entering its lungs

Abstract

The sandfish lizard, Scincus scincus (Squamata: Scincidae), spends nearly its whole life in aeolian sand and only comes to the surface for foraging, defecating and mating. It is not yet understood how the animal can respire without sand particles entering its respiratory organs when buried under thick layers of sand. In this work, we integrated biological studies, computational calculations and physical experiments to understand this phenomenon. We present a 3D model of the upper respiratory system based on a detailed histological analysis. A 3D-printed version of this model was used in combination with characteristic ventilation patterns for computational calculations and fluid mechanics experiments. By calculating the velocity field, we identified a sharp decrease in velocity in the anterior part of the nasal cavity where mucus and cilia are present. The experiments with the 3D-printed model validate the calculations: particles, if present, were found only in the same area as suggested by the calculations. We postulate that the sandfish has an aerodynamic filtering system; more specifically, that the characteristic morphology of the respiratory channel coupled with specific ventilation patterns prevent particles from entering the lungs.

3D Printing: Applications in evolution and ecology

“…An example is the recreation of the airways of Scincus scincus . This species of skink spends its life below the sand, moving in a fish‐like manner, hence its common name “sandfish lizard.” Despite breathing while under the sand, Stadler et al () found no evidence of sand inside dissected sections of the animals’ airways. They theorized that the airways had morphological adaptations, possessing aerodynamic properties which limited sand ingress.…”

“…They theorized that the airways had morphological adaptations, possessing aerodynamic properties which limited sand ingress. To test this, Stadler et al () used computational and 3D printed models. As the airways are small delicate structures they scaled the airways up (changing the working fluid to maintain the ratios of forces acting on the model) and used larger particles of sand.…”

Untitled

“…Another potential benefit of the long, narrow spiracles of Teruelius gen. n. in drier environments is protection of booklungs from particulate contamination by sand and dust. Respiratory systems of some desert animals incorporate mechanisms to exclude fine particles (Stadler et al, 2016;Stebbins, 1943). Entry of sand and dust is probably not an important abiotic factor in humid rainforests where Grosphus is found.…”

Benefits and limitations of three-dimensional printing technology for ecological research

“…In biomechanics, 3D printing is used to test how the shapes of particular appendages or biological structures function in the physical environment without having to use live organisms. For example, 3D printed models of the sand-burrowing sandfish lizard’s ( Scincus scincus ) respiratory system made it possible to study why it does not inhale sand in ways that are impossible with a living lizard’s respiratory system [14]. In studies of fluid dynamics, 3D printed models of swift ( Apus apus ) wings and bodies of echolocating bat species permitted tests in water and wind tunnels respectively to understand how morphology influences species’ movements [15, 16].…”