Abstract
Mass–energy transfer across the boundaries of living systems is crucial for the maintenance of homeostasis; however, it is scarcely known how structural strength and integrity is maintained in extended phenotypes while also achieving optimum heat–mass exchange. Here we present data on strength, stability, porosity and permeability of termite mounds of a fungus-farming species, Odontotermes obesus. We demonstrate that the termite mound is a bi-layered structure with a dense, strong core and a porous shell that is constantly remodelled. Its safety factor is extraordinarily high and is orders of magnitude higher than those of human constructions. The porous peripheries are analogous to the mulch layer used in agriculture and help in moisture retention crucial for the survival of fungus gardens, while also allowing adequate wind-induced ventilation of the mounds. We suggest that the architectural solutions offered by these termites have wider implications for natural and industrial building technologies.
Highlights
Mass–energy transfer across the boundaries of living systems is crucial for the maintenance of homeostasis[1]
All our results, combined together, indicate that termites construct bi-layered mounds with a strong core and a porous periphery; this combination achieves the dual function of extraordinary strength, stability as well as ventilation
Our results suggest that termite mounds are of an intermediate geometry between a triangle and a trapezoid with extraordinarily high safety factors
Summary
Mass–energy transfer across the boundaries of living systems is crucial for the maintenance of homeostasis; it is scarcely known how structural strength and integrity is maintained in extended phenotypes while achieving optimum heat–mass exchange. Mass–energy transfer across the boundaries of living systems is crucial for the maintenance of homeostasis[1] These boundaries can be that of an individual (human skin)[2] or a colony of individuals (swarm cluster of honeybees)[3] or that of a constructed extended phenotype (termite mounds)[4,5]. Homeostasis can be achieved, for example, by regulation of blood flow to skin[2], or the movement of individuals between the periphery and core of a honeybee s warm[3]; little is known about this transfer when the boundary consists of non-living materials, e.g. soil, as in the walls of termite mounds. We further examined the implications of mound geometry in terms of the slope stability and safety factors for a termite mound (see “Methods” for details)
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