Destruction of nematodes by species of Pleurotus

On water agar, Pleurotus ostreatus produces tiny droplets of toxin from minute spathulate secretory cells. Nematodes touching such droplets show a sudden and dramatic response. The head region shrinks considerably; this is accompanied by displacement of the oesophagus and (or) disruption of the tissues surrounding the oesophagus. In as little as 30 s, and usually within several minutes, the nematode becomes more or less immobilized but is not killed. Stimulated by leakage products from the immobilized host, directional hyphae converge on the body orifices of the nematode. These hyphae penetrate one or more body orifices and colonize and digest the host. Pleurotus strigosus, P. subareolatus, and P. cornucopiae behave in a similar way. On potato dextrose agar, P. cystidiosus produces numerous secretory cells, but the toxin is much less potent. On water agar directional hyphae of Pleurotus ostreatus can also be attracted to minute bacterial colonies, which are invaded and apparently digested.

Fungal parasites of bdelloid rotifers: Diheterospora

Descriptions and illustrations are given for 12 species of Diheterospora recovered from parasitized rotifers in Ontario. Four of these species have been previously described and eight are described for the first time.

A new Amoebophilus (Zygomycetes) ectoparasitic on amoebae

Amoebophilus simplex is described as an ectoparasite of amoebae recovered from rotten wood. The short-cylindrical to subclavate conidium attaches by one end to the pellicle of the host, penetrates with a slender germ tube, and produces a lobed haustorium to anchor the thallus and absorb nutrient. Simple or branching chains of conidia are produced from near the apex of the infecting spore. The fungus produces small, polyhedral zygospores which originate from elongate progametangia arising from the conidia in older infections.

Structure and biology of a new Tolypocladium attacking bdelloid rotifers

Tolypocladium lignicola is described as new. The asymmetrical conidia lodge in the mastax of bdelloid rotifers and germinate to produce assimilative infection hyphae composed of elongate, clavate to turbinate, assimilative cells. Conidial production is prolific in air but suppressed under water.

A new predatory hyphomycete capturing bdelloid rotifers in soil

Cephaliophora navicularis, a hyphomycete capable of capturing bdelloid rotifers by using specialized adhesive pegs, is described as new. Canoe-shaped conidia are produced synchronously on ovoid- to club-shaped ampullae that arise more or less directly from the vegetative hyphae. In the presence of rotifers conidia develop short, adhesive appendages by which they attach to the host cuticle. After adhesion, germination and penetration occur and tortuous assimilative hyphae develop in the host. Vegetative hyphae from parasitized rotifers break out to the exterior and produce adhesive pegs which catch additional rotifers.

Structure and biology of a new hyphomycete parasitic on rotifers

Phialophora endoparasitica is described as a new hyphomycete attacking bdelloid rotifers. Infection is initiated by a conidium with a lobed appendage which lodges in the mastax. Conidia germinate to produce branching chains of turbinate assimilative cells which eventually fill the host. Reproductive hyphae break out at a number of points, produce phialidic conidiogenous cells, and release conidia under water.

Two new fungal parasites of bdelloid rotifers

Haptoglossa humicola (Oomycetes) and Tolypocladium trigonosporum (Hyphomycetes) are described as new endoparasites attacking rotifers, belonging to the genera Adineta and Philodina, in soil. In H. humicola the laterally biflagellate zoospores produce spherical cysts each of which then germinates to form a specialized injection cell. The host is attacked by means of rapid injection of a sporidium through the cuticle. Each sporidium produces a thallus inside the host which at maturity functions as a zoosporangium. In T. trigonosporum, after infection, a network of curved anastomosing fertile hyphae produces a loose shell around the encysted host. Conidia are not produced under water, but in air these fertile hyphae give rise to solitary or clustered phialides and triangulate conidia.

A subcuticular endoparasite impaling bdelloid rotifers using three-pronged spores

Triacutus subcuticularis is described as an endoparasite of bdelloid rotifers. The infection hypha does not establish in the visceral tissue but grows in the pseudocoel between the cuticle and the epidermis. In this location the thallus grows and divides repeatedly to produce numerous unicellular assimilative segments which pack the subcuticular space of the living host. After death, each hyphal segment produces one or several filiform extensions which bear solitary one-celled, three-pronged spores at the apex. Infection is initiated by the spore impaling the rotifers in the mouth region.

A new genus of the Zygomycetes

Brachymyces is described as a new genus of the Zygomycetes based on a single species, Brachymyces megasporus, isolated from garden soil. This species produces one to four very large blackish-brown conidia at the apex of short, stout, hyaline conidiophores. In contrast to the massive spores, the vegetative hyphae are extremely fine in diameter (ca. 1.0 μm). Hyphae attack rotifers which become filled with broad, convoluted, assimilative hyphae. Neither resting spores nor sexual spores were observed. The fungus appears to be related to Rhopalomyces in the Helicocephalidaceae of the Mucorales.

Fungal parasites of rotifers: Harposporium

Two new species, Harposporium angularis and Harposporium cylindrosporum, are described as parasitic on a species of bdelloid rotifer belonging to the genus Adineta. In H. angularis the conidia are long, slender, bent at right angles and taper to an acutely pointed slightly curved apex. Infection is initiated by conidia lodging and germinating in the gullet of the host between the mouth and the mastax. In H. cylindrosporum the conidia are also ingested but apparently pass through the mastax to initiate infection in the lower gut.

Fungal parasites of rotifers: a new Tolypocladium with underwater conidiation

A new species, Tolypocladium parasiticum, is described as endoparasitic on the rotifer host Adineta. Unlike most other known Hyphomycetes parasitic on rotifers, conidia are produced underwater. Infection is initiated by conidia lodging in the lower gullet near the mastax of the host. Conidiogenous cells (phialides) arise either directly from the host body or in clusters from short, simple conidiophores. This species produces solitary terminal resting spores with an unusual nodular appearance.

Fungal parasites of rotifers: two new verticillate endoparasites with aerial conidiophores

Diheterospora rotiferorum and Diheterospora ovispora are described as new species endoparasitic on bdelloid rotifers belonging to Philodina and Adineta. In both species resting spores (aleuriospores) are produced underwater and disseminative spores (phialoconidia) are produced from aerial conidiophores. Verticillium reniformis and Acrostalagmus tagenophorus, also endoparasites of rotifers, are transferred to the genus Diheterospora.

Nematophagous fungi: a new Arthrobotrys with nonseptate conidia

Arthrobotrys botryospora is described as new. Conidia are produced in successive clusters on a sympodially elongating main axis. Conidia are mostly nonseptate. Most nematodes are captured by adhesive nets but smaller nematodes are frequently captured by adhesion directly to the vegetative hyphae.

Observations on predatory fungi

In Arthrobotrys flagrans the chlamydospores are formed, following rupture of the primary hyphal wall, by expansion of the inner wall which then produces warty encrustations over its surface. Evidence is presented to show that in Arthrobotrys anchonia none of the water necessary for expansion of the constricting ring cells comes through the stalk cells. Expansion of constricting rings in Dactylaria brochopaga often appears biphasic with little or no constriction of the host cuticle taking place during the first phase of expansion. Microconidia have been found in three species of predatory fungi with constricting rings. In the presence of nematodes, microconidia germinate directly to produce small, functional, constricting rings.

Nematophagous fungi: Hohenbuehelia, the perfect state of Nematoctonus

A predatory Nematoctonus species (N90) isolated from farmyard soil in Ontario produced gill-forming basidiocarps of Hohenbuehelia on potato dextrose agar. In the presence of nematodes, discharged basidiospores germinated to produce short aerial stalks with terminal adhesive knobs. Germinated basidiospores adhered to the cuticle of nematodes to initiate monokaryotic infection cycles. Multiple basidiospore infections on a single host resulted in dikaryotization in the host body. Crossing single basidiospore cultures demonstrated bipolar sexuality for this species of Hohenbuehelia. The implications of these findings are discussed.

Nematophagous fungi: Endoparasites ofRhabditis terricola

Three techniques were compared for the recovery of endoparasitic nematophagous fungi from soil. The Baermann funnel technique (32 species) was superior to differential centrifugation (19 species) or soil sprinkling (21 species) in terms of number of species found. The main advantage of the Baermann funnel was in the recovery of lower fungi, especially those with flagellate states. In all, 40 species of endoparasites (70% of the known flora) were recorded. Thirty-two of those were found capable of attacking the soil nematodeRhabditis terricola Dujardin.

Nematophagous fungi: Protascus and its relationship to Myzocytium

Evidence is presented to support the transfer of Protascus subuliformis to Myzocytium. Based on the nature of the sporangiospores and the method of attacking the host, the known species of Myzocytium parasitic on nematodes are divided into five series. The major characteristics and possible biological advantages of each of these series are outlined. A key to the species of nematophagous Myzocytium species is included.

Nematophagous fungi: three new species of Myzocytium

Three species of Myzocytium parasitic on nematodes are described as new. In M. papillatum the zoospores encyst directly on the host cuticle before penetration. This species produces smooth, spherical oospores. In M. glutinosporum the biflagellate zoospores do not attack the host directly; after encystment they produce a spherical adhesive bud which allows the spores to adhere to the cuticle of passing nematodes. This species produces echinulate, spherical oospores. In M. anomalum the primary spores are aplanospores. After a dormant phase, and when suitably stimulated, these aplanospores change into biflagellate zoospores and the latter encyst on the host cuticle. No sexual state is known in this species. Persistence is by means of thick-walled, spherical chlamydospores.