A hostile takeover
Deep in the high-altitude meadows of the Tibetan Plateau and the Himalayas, a parasitic fungus known as Ophiocordyceps sinensis has a remarkable and macabre life cycle. This organism is an entomopathogenic fungus, meaning it preys on insects, specifically the larvae of ghost moths (family Hepialidae). The infection begins when a microscopic spore lands on a caterpillar. These spores are often sticky, allowing them to adhere to their host. Once attached, the spore germinates, and its hyphae, tiny thread-like filaments, penetrate the caterpillar's exoskeleton.
Inside the host, the fungus begins to proliferate, growing a network of mycelia that fills the insect's body cavity. It methodically digests the caterpillar's non-essential tissues, keeping the host alive for as long as possible. During this phase, the caterpillar's behavior changes; it becomes sluggish as the fungus consumes it from within. The fungus produces a cocktail of bioactive compounds that it uses to manipulate its host, though the exact mechanisms are still under investigation. The fungal cells form a vast network throughout the caterpillar's body, wrapping around muscle fibers but avoiding the brain until the final stages.