Figure 1: The infection cycle of D. coniospora.
Scanning electron micrographs of D. coniospora infecting C. elegans are shown with scale bars. (I) Teardrop-shaped conidia form on individual pegs of the conidiophores on the external surface of the host. (II) Conidial maturation involves the development of one spherical adhesive knob (red arrow) at the distal end of each conidium, after release from the conidiiferous peg and separation from other spores (i.e. conidiogenesis and conidial maturation are spatially separated13). The conidia will remain dormant until attached to a new prey. (III) Conidia specifically adhere near the chemosensory organs on the head and the posterior region of the nematode9,14,15. (IV) Penetration of the nematode cuticle involves a combination of enzymatic action and mechanical force via appressoria, followed by vigorous growth of the trophic hyphae that invade the pseudocoel6,12,15. Invasion through the oesophagus or other natural openings of the nematode has not been observed12. (V) Death of the prey sets in after a short biotrophic phase. New conidiophores develop from bulbs at the tips of trophic hyphae inside the cadaver, tightly oppressed to the internal surface of the cuticle, preventing leakage of host nutrients. (VI) Conidiophores continue to develop while the whole nematode is expended by the fungus, yielding copious amounts (up to 5,000–10,000) of conidia from a single cadaver12.
