Distinct mycelial network architectures during early development of Trichoderma atroviride and Neurospora crassa.

The architecture of filamentous fungi is essential for foraging and the transport of resources, yet little is known about how these structures emerge during early development. We present a comparative, quantitative analysis of early mycelial formation in the model systems Trichoderma atroviride and Neurospora crassa. Using label-free microscopy and automated image processing to extract networks from colonies, we characterized the temporal evolution of two-dimensional (2D) hyphal networks beginning shortly after single-cell germination. We applied the framework of graph theory to evaluate metrics that describe growth dynamics, structure and connectivity for the two species. Both fungi exhibited exponential increase in hyphal tips and branching points (node number), hyphae (edge number), and total mycelium length, consistent with properties of filamentous growth. However, N. crassa displayed faster expansion, greater spatial anisotropy, and a more hierarchical organization dominated by hyphae with high connectivity, whereas T. atroviride formed more isotropic and decentralized networks. Notably, both species developed essentially tree-like architectures and converged to similar fractal dimensions, indicating comparable properties to fill 2D space. These results suggest that early networks in T. atroviride are decentralized, robust and resilient to localized damage, whereas in N. crassa they are hierarchical, favoring rapid and efficient spatial expansion.