Nematophagous Fungi

Abstract Nematophagous fungi are microfungi that can capture, kill and digest nematodes. They use special mycelial structures, the so‐called traps, or spores to trap vermiform nematodes or hyphal tips to attack nematode eggs and cysts before penetration of the nematode cuticle, invasion and digestion. The more than 200 species known differ in saprophytic/parasitic ability. Although many of the trap‐forming and egg‐parasitic fungi can survive in soil saprophytically, the endoparasites are mostly more dependent on nematodes as nutrients. Molecular data have greatly improved our understanding of the function of the fungi in respect of their taxonomy, their physiological/biochemical activity and their ecology, including their function as biocontrol agents. Key Concepts: There are three major groups of nematophagous fungi: the nematode‐trapping fungi that capture free‐living nematodes using specialised morphological structures (i.e. traps), the endoparasitic fungi that infect nematodes using adhesive spores, and the egg‐ and cyst‐parasitic fungi that infect these stages with their hyphal tips. The nematophagous growth habit has evolved several times and independently since nematophagous fungi are found in all major groups of fungi. The nematophagous fungi display a large diversity and extensive plasticity of infection structures. In many species, the formation of trapping‐structures is initiated in response to signals from the environment including compounds secreted by the host nematode. Isolation of more virulent strains, and the development of better formulations and fermentation techniques have significantly improved the efficiency of nematophagous fungi as biological control agents against plant‐ and animal parasitic nematodes. Nematophagous fungi infect nematodes through a sequence of events including adhesion of the trapping structures to the host nematode surface, followed by penetration, killing and digestion of the nematode tissues. The secretion of extracellular enzymes such as serine proteases and chitinases are required for successful parasitism of free‐living nematodes and nematode‐eggs by nematophagous fungi.