Gonimochaete lignicola is described as a new species of nematode-destroying endopar? asite recovered from rotting wood. Segments of the infection thallus function as sporangia and produce solitary aerial evacuation tubes. The protoplasm in the sporangium migrates to the swollen tip of the evacuation tube where it differentiates into spores. The tip of the evacuation tube is cut off by a septum from the vacuolated remainder either before or after spore formation. Some thalloid segments function as antheridia or oogonia. The protoplasm migrates from the antheridium into the oogonium and a solitary, thick-walled, pitted oospore is produced. This is the first time the sexual state has been described for a species of Goni? mochaete and supports placement of this genus in the Lagenidiales. The genus Gonimochaete was erected by Drechsler (1946) based on a single species, G. horridula Drechsler, which parasitized nematodes in decomposed leaves of red maple, gathered near a pond in Delaware. Later, Barron (1973) described G. pyriforme as a parasite of the nematode Diploscapter in greenhouse soil. A third species, G. latitubus, was discovered by Newell et al. (1977) attacking rhabditid nematodes inhabiting the marine littoral zone in southeastern Florida. The sexual state was not reported for any of the described species. Gonimochaete horridula is remarkable in producing non-motile spores which gather in clusters at the mouths of aerial evacuation tubes. Each aplanospore produces an adhesive knob which may attach to the host and infect it by direct penetration through the cuticle. As it develops, the infection thallus breaks up into segments each of which eventually functions as a sporangium and produces a solitary evacuation tube which is elongate and oriented more or less vertically. The body of the sporangium becomes vacuolate and the dense protoplasmic contents are pushed up the evacuation tube. Spores are formed by horizontal cleavage of the protoplasm inside the tube and the mature spores are pushed to the exterior through an exit at the tip to form an aerial cluster of aplanospores. The evacuation tube now functions as a support stalk for the ejected spore mass. Turgidity of the evacuation tube is maintained by the formation of a cross wall at its tip. Thus the sporangium and associated support stalk probably remain alive for some time after spore release. A previously undescribed species of Gonimochaete was recovered during a study of parasites of rotifers and nematodes in rotting wood. In the size and shape of the spores, and in their manner of production, this species differs significantly from previously described species. Moreover, it produces oogonia, antheridia, and oospores similar to those found in some species of Mycocytium (Lagenidiales). Methods used to recover this fungus and study its life cycle have been described previously (Barron, 1977b).
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Jan 1, 1990
Jan Dijksterhuis + 2
Open Access