a genus of 30 species of fungi in the order Helotiales (phylum Ascomycota, kingdom Fungi) that exists as asexual forms (anamorphs) and captures and kills nematodes (roundworms). Once prey is captured, a penetration tube grows out of a hypha (one of the filaments that make up the body of a typical fungus) and enters the body of the prey. The hypha then begins to grow and branch, forming haustoria (haustorium) (special absorbing structures). Enzymes secreted by the fungus kill the nematode.