A New Haptoglossa Attacking Rotifers by Rapid Injection of an Infective Sporidium

SUMMARY

Haptoglossa mirabilis is described as a new endoparasitic oomycete attacking Adineta rotifers. A solitary infection produces a large, cylindrical thallus with rounded ends. At maturity each thallus functions as a zoosporangium producing one or several evacuation tubes through which laterally biflagellate zoospores escape. Zoospores encyst after a swarming period. Each encysted zoospore then germinates to produce a remarkable hypodermic-like infection cell. Using this cell, the fungus attacks rotifers by rapid injection of a walled, cylindrical sporidium which enlarges to become the thallus.