A nonoccluded virus in nymphs of the dragonfly Leucorrhinia dubia (Odonata,Anisoptera)

This work establishes the sequence of events as the water mold, Coelomomyces psorophorae, develops and enters mosquito larvae through the cuticles of these insects. The fungal cyst shows a number of adaptations for a parasitic function. A bulb-shaped appressorium is produced at germination which is initiated and/or maintained by a microtubular skeleton. The tip of the appressorium secretes a dense amorphous substance, then produces a narrow penetration tube which grows through the larval cuticle. The penetration tube maintains its narrow diameter as it grows inside the host epidermal cell. The parasite protoplasm is injected into a host epidermal cell. The protoplast is squeezed through the narrow tube by the (probably rapid) expansion of a vacuole in the cyst body at the end distal to the penetration point. There is a correlation of cuticular texture with adhesion patterns of cysts. A cuticular collar is always seen in successful penetrations. The sequence of development after attachment of the fungal zygotes is: germination between 1 and 2 hr; penetration between 3 and 4 hr; and injection between 6.5 and 8 hr.