The Cauxi sponge, a resident of the Amazon Basin, is a freshwater sponge with impressive adaptability. Belonging to the Demospongiae class, it can be considered a natural mineral-organic composite comprising sub-millimeter spicules embedded in an organic matrix, which acts as an adhesive layer. Two types of spicules are observed in a specimen from the Guaporé River: megascleres (about 150 µm long and 20 µm in diameter) and microscleres (50 µm long and 10 µm in diameter). Electron microscopy reveals that these spicules form a homogeneous, amorphous silica structure. We report the compressive strength of the spicules, obtained from micropillars, their modulus, revealed by nanoindentation, and their fracture toughness, tested using a pre-notch micro cantilever beam. The mesoporous nature of the biogenic silica is evaluated by SAXS data, showing pore sizes around 2.3 nm. Additionally, we revealed the shell structure of Cauxi gemmules, which are reinforced by short silica spicules acting as reinforcing struts. This discovery of mesoporous structures, synthesized under ambient conditions, inspires the design of artificial lightweight protective shell structures comprised of short fibers with disk-like extremities connected by an organic matrix.

Mycelium-based composites are gaining significant attention as sustainable, biodegradable materials for applications ranging from construction to packaging. Our research examines two key bracket fungi—Ganoderma lucidum (Reishi) and Fomes fomentarius—focusing on their structural hierarchy and mechanical behavior. For G. lucidum, we characterized fruiting bodies with a trimitic hyphal network comprising a dense crust, a porous context, and vertically oriented, segmented hymenial tubes. Micro-computed tomography (µCT) revealed how tube segmentation enables staged buckling and crack deflection, boosting energy absorption. Meanwhile, in F. fomentarius (historically used for amadou production), we specifically investigated its context layer, where variations in hyphal organization and density critically influence tensile performance and damage tolerance. Through structural and chemical analysis, mechanical testing, and in situ SEM characterization—including comparisons with commercial mycelium composites—we show how pore architecture, hyphal bundling, and compositional gradients collectively govern the distinct, tunable properties of these fungal materials.

The hierarchical designs of both fungi provide valuable blueprints for robust, lightweight bioinspired materials. Implementing these natural principles could advance sustainable industrial solutions with closed-loop life cycles, particularly improving load-bearing capacity, damage tolerance, and energy absorption in engineered systems.