Nature's Ballistic Missile

The parasitic fungus Haptoglossa mirabilis infects its rotifer host by means of a gun-shaped attack cell. The anterior end of the cell is elongated to form a barrel; the wall at the mouth is invaginated deep into the cell to form a bore. A walled chamber at the base of the bore houses a complex, missile-like attack apparatus. The projectile is fired from the gun cell at high speed to accomplish initial penetration of the host.

Carnivorous mushrooms

Ten species of gilled fungi, including the oyster mushroom (Pleurotus ostreatus), have been shown to attack and consume nematodes. It is suggested that these wood-decay fungi utilize the nutrients in their prey to supplement the low levels of nitrogen available in wood. This mode of nutrition is similar in principle to that of carnivorous higher plants.

Parasitism of algae by lignicolous Basidiomycota and other fungi

On water agar, 30 out of 81 species of fungi tested showed positive directional hyphal growth towards microcolonies of the green alga Protococcus sp. and produced coralloid masses of branched assimilative hyphae within the invaded algal colonies. Of 77 species of fungi tested against the blue-green alga Synechococcus elongatus, 33 exhibited this same phenomenon. Cell walls of S. elongatus were subsequently lysed while only cell death occurred in Protococcus sp., resulting in the release of the contents that were presumably absorbed by the coralloid hyphae. Branched hyphae from some invading fungi occasionally attached to larger individual cells of Protococcus sp., penetrated the walls, and absorbed the contents. Key words: algae, Chlorophyta, Cyanophyta, cyanobacteria, Basidiomycota, wood decay, nitrogen requirements, Protococcus, Synechococcus.

Parasitism of yeasts by lignicolous Basidiomycota and other fungi

On water agar, hyphae of certain fungi are able to attack microcolonies and even solitary cells of yeasts belonging to the genera Candida, Cryptococcus, Pichia, Rhodotorula, and Sporidiobolus. The ability to attack yeasts is particularly common among the Basidiomycota and 100 of 195 isolates tested positive. In the Ascomycota and Deuteromycota, only 12 of 128 isolates tested positive. Two species of the Oomycota and 10 species of the Zygomycota tested negative. Two types of initial responses were recorded: (i) a chemotropic response in which directional hyphae are attracted to microcolonies or solitary cells, and (ii) a contact response in which hyphae reach yeast colonies by chance and subsequently attack them. In both cases the invading fungus produces coralloid masses of branched assimilative hyphae within the yeast colonies. Yeast cells are utilized as a nutrient source by the invading fungus in either of two ways: (i) the walls of yeast cells are lysed releasing the contents that are absorbed by the coralloid hyphae or (ii) branched hyphae from the invading fungus attach to the yeast cells, penetrate the walls, and absorb the contents. Both methods involve necrotrophic mycoparasitism. Keywords: yeasts, Basidiomycota, necrotrophic mycoparasitism, wood decay, nitrogen requirements.

A new Harposporium with triangular conidia attacking bdelloid rotifers

Harposporium trigonosporum is described as new. After ingestion by rotifers, the traingular conidia lodge any place between the mouth and the anus but most frequently in the lower gut. A filiform germination hypha develops from each corner of the conidium and penetrates through the gut wall into the body cavity of the host. The host frequently responds to this invasion by laying down deposits around the advancing germ tube that sometimes causes the germinating conidium to abort. More frequently a germination hypha breaks through the host deposits at one or more of the three points of attack and proliferates inside the body, resulting in the death of the rotifer. Key words: Harposporium, endoparasite, rotifer.

A new genus of the Hyphomycetes endoparasitic in bdelloid rotifers with conidia that lodge in the mastax

Haptospora is described as a new genus of the Hyphomycetes endoparasitic in rotifers. The genus is distinguished by conidia that have a doughnut-shaped modification at the base. This structure appears to have a function in lodging the conidium in the mastax of the host. The conidiogenous cells are phialides, each with a membranous collarette. Two species of Hyphomycetes, described previously as Phialophora endoparasitica and P. tribrachispora, are transferred to Haptospora, and a third species, Haptospora appendiculata, is described as new. Key words: Phialophora, Haptospora, endoparasite, rotifer.

A new genus, Rotiferophthora, to accommodate the Diheterospora-like endoparasites of rotifers

The species of Diheterospora attacking bdelloid rotifers have been compared with Diheterospora chlamydosporia and found to be different in a number of important characteristics. These include the consistent presence of aphanophialides, proliferation of phialides and aphanophialides to form polyphialides, containment of the conidial mass in a hydrophobic membrane, reduction or elimination of the verticillate arrangement of the conidiogenous cells, and presence of a large oil droplet in each conidium. It is considered that these differences are sufficient to separate the rotifer parasites from both Diheterospora and Verticillium. Accordingly, a new genus, Rotiferophthora, is erected to accommodate the 17 species recognized in this group of fungi. Thirteen rotifer parasites previously described under Diheterospora, Verticillium, or Acrostalagmus are transferred to Rotiferophthora, and four new species of Rotiferophthora are described. Key words: Diheterospora, Rotiferophthora, endoparasite, rotifer.

A new predatory Hyphomycete capturing copepods

Dactylella copepodii sp.nov. is described as a new predatory Hyphomycete capturing larval and adult stages of soil-inhabiting copepods. Capture is by adhesion to the swollen end cell of a hypha or lateral branch. Conidiophores are simple and each bears a large, hyaline, multiseptate, terminal, solitary conidium. In the presence of copepods, conidia germinate from the end cells to produce simple or sparingly branched hyphae bearing adhesive knobs at the tips. The relationship between Dactylella and Monacrosporium is discussed.

New Cephaliophora species capturing rotifers and tardigrades

Cephaliophora muscicola and Cephaliophora longispora are new species of Hyphomycetes capturing rotifers and tardigrades using specialized adhesive pegs. Elongate, hyaline, multiseptate, canoe-shaped conidia are produced synchronously in small clusters at the apex of conidiophores, which arise at right angles from the vegetative hyphae. In the presence of rotifers, conidia germinate to produce one or several adhesive pegs. Rotifers and tardigrades are captured by the pegs, and subsequent growth forms an extensive network of hyphae bearing pegs and clusters of conidia. Cephaliophora muscicola was recovered from moss and forest debris in New Zealand and from leaf mould in Japan. Cephaliophora longispora was removed from mossy soil collected in New Zealand and from moss in Canada.

A new and unusual species of Haptoglossa

Haptoglossa elegans, isolated from soil and organic debris in New Zealand forests, is described as new. This species has no motile stage. The protoplasm inside the thallus cleaves into spherical cysts that are expelled en masse to the exterior through a solitary exit tube. Cysts are two sizes. Small cysts produce elongate, unbranched, tapering gun cells. Large cysts produce identical but larger cells; alternatively large cysts produce Y-shaped gun cells. Haptoglossa elegans is a common and aggressive parasite of bdelloid rotifers but unlike all other species of Haptoglossa, it does not attack nematodes.

Host range studies for Haptoglossa and a new species, Haptoglossa intermedia

Haptoglossa intermedia sp.nov., recovered from woodland soil, is described as a new endoparasite of rotifers. The species is distinguished from others by the shape and size of the gun cell, the fusiform infection sporidia, and the shape of the thalli. This species, along with H. zoospora, H. mirabilis, and H. humicola, can attack and complete its life cycle on both rotifers and nematodes. Tardigrades (water bears) may be alternative hosts for Haptoglossa species.

Biological Control of Meloidogyne hapla on Alfalfa and Tomato with the Fungus Meria coniospora

This study was to determine whether Arthrobotrys flagrans, A. oligospora, and Meria coniospora would control the root-knot nematode Meloidogyne hapla on alfalfa and tomato. Alfalfa seeds were coated with a fungus-rye powder in 2% cellulose and were planted in infested soil. Three-week-old seedlings from seed treated with M. coniospora had 60% and 58% fewer galls in two experiments than did seedlings from untreated seeds. Numbers of J2 in the soil were not reduced. Plant growth did not improve. When seed of tomato were coated with M. coniospora and planted in M. hapla-infested soil, roots had 34% fewer galls and 47% fewer J2 in the soil at 28 days. After 56 days there was no reduction in J2 numbers. Plant growth did not improve. When roots of tomato transplants were dusted with M. coniospora fungus-rye powder or sprayed with a spore suspension before planting in M. hapla-infested soil, 42% and 35%, respectively, fewer galls developed in 28 days on treated roots than on roots not treated with fungus. The numbers of J2 extracted from roots or recovered from soil were not reduced, however, and plant growth did not improve.

New species and new records of fungi that attack microscopic animals

Three species of fungi that attack microscopic animals are described as new. Verticillium coronatum (Hyphomycetes) produces conidia that have a cluster of small, apical appendages. The appendages function in attaching the conidia to the cuticle of the host nematode in the initial stages of infection. Diheterospora humicola (Hyphomycetes) was found to attack bdelloid rotifers in soil. Infection of the host is initiated by ingestion of conidia. Lagenidium oviparasiticum (Oomycetes) is an aggressive parasite of the eggs of Adineta rotifers. Zoospores of the fungus encyst on the egg shell, penetrate, and transfer their contents into the egg to initiate infection.

Microcolonies of bacteria as a nutrient source for lignicolous and other fungi

Under low nutrient conditions hyphae of certain fungi are strongly attracted to microcolonies of bacteria belonging to the genera Pseudomonas and Agrobacterium. Hyphae of the fungi penetrate the microcolonies and proliferate to produce coral-loid, haustorial-like masses of absorptive hyphae. The bacteria in the colonies are lysed and the contents apparently absorbed as a nutrient source by the fungi. The four fungi that demonstrated this capability were Agaricus brunnescens (= A. bisporus), Coprinus quadrifidus, Lepista nuda, and Pleurotus ostreatus. Approximately 100 additional species belonging to the Basidiomycota, Oomycota, Zygomycota, Deuteromycota, or Ascomycota were also tested, but none were found capable of attacking and digesting bacterial colonies in this way.

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.