Info

- Ascomycota

Nematode-trapping fungi:

Arthrobotrys/Orbilia (adhesive networks) Dactylellina/Orbilia (adhesive knobs and/or non-

constricting rings Drechslerella/Orbilia (constricting rings) Gamsylella/Orbilia (adhesive branches or unstalked knobs)

Endoparasitic fungi:

Harposporium/Podocrella (ingested conidia) Drechmeria (adhesive conidia) Haptocillium (adhesive conidia)

Egg- and female-parasitic fungi:

Pochonia/Cordyceps (appressoria) Paecilomyces (appressoria)

Zygomycota

Chytridiomycota

Oomycota

Endoparasitic fungi:

Myzocytiopsis (zoospores) Haptoglossa ("gun cells", injection)

Egg- and female-parasitic fungi:

Nematophthora (zoospores)

Nematode-trapping fungi:

Stylopage (adhesive hyphae) Cystopage (adhesive hyphae)

Endoparasitic fungi:

Catenaria (zoospores)

Figure 2. Taxonomic position of nematophagous fungi with examples of genera. The first genus names are anamorphs, and genus names after slashes indicate known teleomorphs. Infection structures are shown in parenthesis.

Most nematode-trapping species have a teleomorph within Orbilia, and their taxonomic positions have been arranged according to their type of trapping device (Ahrén, Ursing, & Tunlid, 1998). Scholler, Hagedorn, and Rubner (1999) suggested the following classification based on molecular data: Arthrobotrys (adhesive three-dimensional networks), Dactylellina (stalked adhesive knobs and/or non-constricting rings), Drechslerella (constricting rings) and Gamsylella (adhesive branches and unstalked knobs). This classification was questioned by Li et al. (2005) who suggested that the species in Gamsylella should be transferred to either Arthrobotrys or Dactylellina based on more and refined DNA sequencing. In this review we follow the taxonomy suggested by Scholler et al. (1999). Li et al. (2005) put forward a hypothesis of an evolutionary pathway of traps of the nematode-trapping Orbiliales. According to this hypothesis, two lines have evolved originating from adhesive knobs, in one line the adhesive was lost and evolved to form constricting rings, whereas the other evolutive line retained the adhesive and became three-dimensional networks.

Much less is known about the taxonomy/phylogeny of the endoparasitic fungi. Some of these are placed in the Chytridiomycetes, e.g. the zoosporic Catenaria anguillulae, others in Haptocillium (formerly Verticillium), Harposporium or Drechmeria. The teleomorph of Harposporium spp. has recently been transferred from Atricordyceps to Podocrella (Chaverri, Samuels, & Hodge, 2005). The basidiomycete genus Hohenbuehelia (anamorph: Nematoctonus) contains fungi that can be classified as both nematode-trapping and endoparasites (Thorn & Barron, 1986). The genus Pleurotus includes species, such as the oyster mushroom P. ostreatus, and constitutes the toxin-producing fungi. Recently, Coprinus comatus was shown to have similar capabilities (Luo, Mo, Huang, Li, & Zhang, 2004), suggesting that the nematophagous habit may be more widespread among Basidiomycetes than previously thought.

2.3. Fungal Parasites of Invertebrates

Entomopathogenic and nematophagous fungi are generally facultative parasites, usually implying a low host specificity and consequently a wide host range. They can also colonize a wide array of habitats and their main species can be found worldwide.

Entomopathogenic and nematophagous fungi bear multiple similarities. The most important species of both fungal groups have been described as soil inhabitants, where they spend most of the saprophytic growth phase. Soil is also the environment of nearly all plant-parasitic nematodes and of soil dwelling insects such as roots pests or other underground plant organs. For further details on these aspects see Lopez-Llorca and Jansson (2006).

Pochonia Rubescens

Figure 3. Mode of action offungal parasites of nematode eggs. (a) Field emission scanning electron microscopy (FESEM) of nematode (Heterodera schachtii) egg inoculated with conidia of Pochonia rubescens (Bar = 25 ¡m). (b) Detail of the fungus appressoria showing adhesive secretions on the eggshell (Bar = 2 ¡m). (c) Labelling of nematode-infected egg with Con A lectin fluorescently labelled (Bar = 25 ¡m). (d) Detail of advanced infection by P. rubescens showing fully developed appressoria on eggshell (Bar = 5pim). (e) Eggshell penetration by P. rubescens (Bar = 0.25 ¡m). (f) immunofluorescence detection of P32 protease produced by P. rubescens (Bar = 5 ¡m). (g) Immunogold detection of P32 (Bar = 1 ¡m) (Lopez-Llorca & Robertson, unpublished). (h) and (i) Effect of purified P32 on eggshell of H. schachtii. (h) control (Bar = 5 ¡m) and (i) P32-treated. (Bar = 10 ¡m). (FESEM, Lopez-Llorca & Claugher, unpubl.). (a) From Lopez-Llorca and Claugher, 1990, courtesy of Elsevier. (c) From Lopez-Llorca, Olivares-Bernabeu, Salinas, Jansson, and Kolattukudy, 2002b, courtesy of Elsevier. (d) and (e) adapted from Lopez-Llorca and Robertson, 1992b, courtesy of Springer. f) From Lopez-Llorca and Robertson, 1992a, courtesy of Elsevier.

Figure 3. Mode of action offungal parasites of nematode eggs. (a) Field emission scanning electron microscopy (FESEM) of nematode (Heterodera schachtii) egg inoculated with conidia of Pochonia rubescens (Bar = 25 ¡m). (b) Detail of the fungus appressoria showing adhesive secretions on the eggshell (Bar = 2 ¡m). (c) Labelling of nematode-infected egg with Con A lectin fluorescently labelled (Bar = 25 ¡m). (d) Detail of advanced infection by P. rubescens showing fully developed appressoria on eggshell (Bar = 5pim). (e) Eggshell penetration by P. rubescens (Bar = 0.25 ¡m). (f) immunofluorescence detection of P32 protease produced by P. rubescens (Bar = 5 ¡m). (g) Immunogold detection of P32 (Bar = 1 ¡m) (Lopez-Llorca & Robertson, unpublished). (h) and (i) Effect of purified P32 on eggshell of H. schachtii. (h) control (Bar = 5 ¡m) and (i) P32-treated. (Bar = 10 ¡m). (FESEM, Lopez-Llorca & Claugher, unpubl.). (a) From Lopez-Llorca and Claugher, 1990, courtesy of Elsevier. (c) From Lopez-Llorca, Olivares-Bernabeu, Salinas, Jansson, and Kolattukudy, 2002b, courtesy of Elsevier. (d) and (e) adapted from Lopez-Llorca and Robertson, 1992b, courtesy of Springer. f) From Lopez-Llorca and Robertson, 1992a, courtesy of Elsevier.

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