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Nematophagous fungi
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"線蟲捕食菌 (nematophagous fungi)"食線蟲真菌是專門捕獲和消化線蟲的捕食真菌，可依靠菌絲體構成的特殊陷阱和圈套來捕食線蟲或其他原生生物，或以寄生、分泌毒素的方式，殺死線蟲，從而獲得養分。大約有160種。只要有線蟲的地方(土壤、植物----寄生或腐生、河川、海洋)皆有此類真菌(主要生活在缺氮<ref>Liquid error: wrong number of arguments (1 for 2)</ref>的棲息地)。
==種類==
依照不同的取食方式，分成5大類:
1.捕捉/獵食性(Nematode-trapping /predatory fungi): 菌絲主要存在土壤或植物殘體，利用特殊構造捕捉線蟲，包含以下6種捕捉構造:
"黏著性網(Adhesive nets)":有黏性，但無法收縮。當線蟲接觸到菌網時，菌網分泌出大量黏液捕獲線蟲，菌絲侵入線蟲並形成球形結構，然後產生大量的菌絲填滿蟲體腔，逐漸耗盡蟲內的營養。例如: ''Arthrobotrys''
<ref>Liquid error: wrong number of arguments (1 for 2)</ref>
"非收縮環(Non-constricting or detachable rings)":可和菌絲一起脫落。環狀結構由三個細胞融合而成，此環能分泌黏性物質，其柄長而細弱，線蟲一旦套住後，易被折斷而脫落，並被線蟲帶走，仍保有發芽的能力。同一菌絲通常有非收縮環結構者必有黏著球結構並存。例如: ''Monacrosporium
''
"收縮環(Constricting rings)":無法隨菌絲脫落。為一個三細胞環結構，其柄短而結實，當線蟲穿過環時，菌環細胞的直徑會急劇變大，長度縮短，內徑縮小，線蟲被緊緊收縮在菌環中，麻痺而死亡，菌絲穿入線蟲並大量產生。<ref>Liquid error: wrong number of arguments (1 for 2)</ref>
"黏著球(Sticky (adhesive) knobs)":無法隨菌絲脫落。從菌絲的分支頂端長出之特化膨大具有黏性的菌球。黏性物質在球的表面形成一層薄層，線蟲先黏到一個球上，在線蟲掙扎過程中會觸碰到更多的黏性菌球並被緊緊困住，菌球上長出菌絲穿入線蟲體內形成球狀體，再從此球上長出大量菌絲充滿蟲體 ，例如: ''Monacrosporium'' 、擔子菌中''Hohenbuehelia'' (亞側耳) 和''Resupinatus'' (伏褶菌)，可在木頭內形成滴漏狀(hour-glasses)的黏性菌球
"黏著性分支(Sticky (adhesive) branches) "
"黏性菌絲(Sticky (adhesive) hyphae)":主要為接合菌中的捕蟲黴菌門，菌絲產生黏性物質覆蓋在菌絲表面而有黏性，亦可捕捉其他原生生物，無法經由人工培養。這類構造捕蟲能力較強，當線蟲接觸黏性菌絲後，儘管只有一個接觸點，線蟲也會立即被黏住而失去活動力，黏性菌絲即刻產生侵染菌絲從接觸點侵入蟲體吸收營養，殺死蟲體。例如: ''Acaulopage''
2.內寄生性(Endoparasitic): 此類菌主要以線蟲為營養為一來源 (絕對寄生性)，以孢子感染蟲體。菌體主要存在於線蟲寄主，並不會在土壤內長距離延伸，產生的孢子經由體表黏附(Attach to nematode cuticle)和攝入線蟲(Ingested by nematode)來感染線蟲，孢子在線蟲體內發芽後穿透至線蟲體外，並於線蟲體外產生孢子。
"Attach to nematode cuticle":又分為兩種
可藉由游走孢子(motile spores)內寄生，例如: ''Catenaria''(Chytridiomycota)、''Myzocytium'' (Oomycota)、''Lagenidium'' (卵菌)
可藉由黏性孢子(adhesive spores)內寄生，例如: Haptocillium( sticky conidia)、Ｈirsutella (Ascomycota)用Adhesive conidia (spores)
"Ingested by nematode":藉由吞食性孢子(ingested spore)，有不同形狀，可被線蟲取食進入腸道中，卡在體內發芽，形成孢子。例如: ''Harposporium anguillulae<ref>Liquid error: wrong number of arguments (1 for 2)</ref>'' (Ascomycota) (anamorph用non-adhesive conidia被線蟲攝入)
3.Injected spores:彈射孢子感染線蟲，為絕對寄生。大多數為卵菌，少數為接合菌。死後的線蟲直接產生孢子囊梗(螺旋狀扭曲)，彈射出孢子感染線蟲。若孢子無遇到寄主，會直接在基質上形成厚膜孢子，等待機會感染。例如: ''Haptoglossa mirabilis'' (Oomycota)
4. Parasites of eggs or cysts:寄生在線蟲的不動結構，卵(eggs)<ref></ref>或胞囊(cysts)<ref>Liquid error: wrong number of arguments (1 for 2)</ref>。為伺機性的(Opportunistic)本身殘存於土壤環境中，行腐生 ，非絕對寄生，並無特化的感染構造，主要以菌絲感染。例如: ''Pochonia chlamydosporia'' (Anamorph)、''Metacordyceps chlamydosporia''(Teleomorph 、Clavicipitaceae 麥角菌科)、''Purpureocillium lilacinus''
除了''Nematophthora gynophilis'' (oomycetes)以游走孢子(zoospore)感染線蟲的胞囊。
5. Kill by toxins:分泌毒素毒殺線蟲。例如: 側耳屬 (''Pleurotus<ref>Liquid error: wrong number of arguments (1 for 2)</ref>'')特化細胞在菌絲周圍形成滴狀毒素，使線蟲麻痺死亡；
薄殼菌屬 （''Hyphoderma''）屬於擔子菌亞門皮殼菌Corticiaceae目之種類，其對線蟲有捕捉及毒殺現象
"捕捉": 有些種可以以一室或二室之冠囊体<ref></ref> （stephanocyst，從菌絲上側生出或直接從孢子產生的球形細胞，其基部環生一圈小刺結構）捕捉、黏著松材線蟲之後侵入寄生並加以毀滅
"毒殺": 有些種則細胞質所具之毒性物質（毒素），當細胞質被松材線蟲取食後，即可將其毒殺，再產生短側枝侵入線蟲體腔，破壞其器官、組織，並將其分解、吸收其組成分
==生態學==
"捕捉/獵食性(Nematode-trapping /predatory fungi)真菌":
1.主要是以腐生營養，以線蟲來補充其N源
2.大部分種類之捕捉構造需要有線蟲存在時產生 (受線蟲分泌物的刺激)，生物防治效率不高，因為菌種在土壤中易被稀釋，需線蟲保持其高濃度的菌量。
3.捕捉性真菌並無寄主之偏好
4. Adhesive nets、Non-constricting or detachable rings、Constricting rings、Sticky (adhesive) knobs、Sticky (adhesive) branches大多存於高等真菌中無性繁殖的不完全菌
5. 6種捕捉構造(除constricting rings外)皆為adhesive，黏著性
6. 感染為irreversible (不可逆的)，一旦啟動了感染，縱使線蟲掙脫，捕捉構造仍會黏附在線蟲身上，並持續感染之
7. 許多nematode-trapping fungi之有性時期為盤菌之Orbiliales目的種類，子實體小，大量聚集透明狀且有不同顏色
"內寄生性(Endoparasitic)真菌"生態學:
1.有些內寄生菌有寄主之偏好性，如寄生性線蟲的口器就不適合取食Harposporium之孢子，所以無法感染
2.所以屬於"Ingested by nematode"之種類無法用於生物防治寄生性線蟲， "Attach to nematode cuticle"的種類則可
==多樣性==
在世界各地的各種棲息地和氣候中都發現了食線蟲真菌，但很少來自極端環境。研究最多的是攻擊農業生產線蟲的物種，但仍有許多物種未被探討。Orbilia的有性階段發生在陸地或淡水中的腐爛木材上，而無性階段發生在海洋，淡水和陸地棲息地。''Arthrobotrys dactyloides''是在鹹水中發現的第一個物種，而亦在紅樹林中發現了其他物種。
==生物防治==
1. Duddingtonia flagrans(為Orbiliales中的捕食性真菌):用於生物防治動物線蟲病害，無法殺死草食動物體內之線蟲 (主要是殺死糞便內之線蟲)，將孢子餵食動物，孢子會在糞便中發芽生長，產生捕捉構造捕捉線蟲，草上的線蟲擴散率降低，草食動物不易吃到線蟲，僅是防止二次感染，殺死體內已存有的線蟲，所以仍要配合驅蟲藥劑服用。防治時，必須要持續餵食真菌孢子才能達到治療效果
2.植物寄生性線蟲具有針狀口器，無吞噬能力，無法用內寄生真菌的攝入線蟲(Ingested by nematode)途徑來感染線蟲，但可用體表黏附(Attach to nematode cuticle)方式。但對於腐生性線蟲的話，其吞噬孢子的能力較佳，則用內寄生真菌的攝入線蟲(Ingested by nematode)途徑來感染線蟲
3.''Purpureocillium lilacinus''<ref></ref>可做為微生物防治劑，用其菌絲感染線蟲的卵
4薄殼菌屬 （''Hyphoderma''）此等菌類之生態習性和松材線蟲接近，對松樹又不具病原性，故具防治松材線蟲潛能。由於冠囊體表面之黏液醣蛋白，和松材線蟲体表之醣蛋白的互補作用，而產生專一性之辨識作用
[[Image:20100814 175958 FungusOnDeadnematode HarposporiumAnguillulae.jpg|thumb|right|A dead nematode with ''[[Harposporium anguillulae]]'' growing out of it. Numbered ticks are 122 µm apart.]]
[[Image:20100814 180201 FungusOnDeadnematode HarposporiumAnguillulae.jpg|thumb|right|A closer look at ''H. anguillulae'' fungi from the previous image. Numbered ticks are 20 µm apart.]]
[[Image:20100828 005957 Fungus.jpg|thumb|right|A fungus of the genus ''[[Arthrobotrys]]'', showing adhesive nets which it uses to trap nematodes. Numbered ticks are 122 µm apart.]]
'''Nematophagous fungi''' are [[carnivorous fungus|carnivorous fungi]] specialized in trapping and digesting [[nematode]]s. Around 160 species are known. There exist both species that live inside the nematodes from the beginning and others that catch them, mostly with glue traps or in rings, some of which constrict on contact. Some species possess both types of traps. Another technique is to stun the nematodes using toxins, which is a method employed by ''[[Coprinus comatus]]'', ''[[Stropharia rugosoannulata]]'', and the family [[Pleurotaceae]].<ref name="thorn00"></ref> The habit of feeding on nematodes has arisen many times among fungi, as is demonstrated by the fact that nematophagous species are found in all major fungal groups.<ref></ref> Nematophagous fungi can be useful in controlling those nematodes that eat crops. ''[[Purpureocillium]]'', for example, can be used as a bio-[[nematicide]].
==Types==
Fungi that feed on nematodes (as the most abundant and convenient prey species) mostly live in nitrogen-deficient habitats.<ref name=Hsueh></ref> These fungi can be divided into four main groups according to the methods they use to catch their prey. Some use a mechanical means, an adhesive or a mechanical [[hypha]]l trap. Some produce a toxin and use it to immobilise the nematode. Some are [[Parasitism|parasitic]], using their spores to gain entry into their prey, and some are egg parasites, inserting their hyphal tips into the eggs or cysts, or into females before the eggs are deposited.
==Diversity==
Nematophagous fungi have been found throughout the world in a wide range of habitats and climates, but few from extreme environments. Most studied have been the species that attack the nematodes of interest to farmers, horticulturists and foresters, but there are large numbers of species as yet undescribed. The sexual stage of ''[[Orbilia]]'' occurs on rotting wood on land or in fresh water, while the asexual stage occurs in marine, fresh water and terrestrial habitats. ''[[Arthrobotrys dactyloides]]'' was the first species to be discovered in [[brackish water]], and other species have been found on [[mangrove]]s.
==Ecology==
Nematode-trapping fungi are mostly concentrated in the upper part of the soil, in [[pasture]]s, [[leaf litter]], [[mangrove]]s and certain shallow aquatic habitats. They employ techniques such as adhesive hyphal strands, adhesive knobs, adhesive nets formed from hyphal threads, loops of hyphae which tighten round any ensnared nematodes and non-constricting loops. When the nematode has been restrained, the hyphae penetrate the cuticle and the internal tissues of the nematode are devoured.
It has been found that ''[[ Arthrobotrys oligospora]]'', a net-building species of fungus, can detect the presence of nematodes nearby in the soil and only builds its snares when they are present. This is presumably because building the net is a highly energy-consuming process; the fungus is alerted to the presence of the nematode by detecting the [[pheromone]]s, such as [[ascaroside]]s, with which the worms communicate. The fungus takes active steps to attract its prey by producing olfactory cues that mimic those used by the worm to find food and attract mates.<ref name=Hsueh/> ''Arthrobotrys dactyloides '' is a species that employs a loop of hypha to catch nematodes; when one tries to pass through the ring, the loop constricts with great rapidity, trapping the prey.
[[File:Schopftintling-Coprinus-comatus.jpg||upright|thumb|The hyphae of [[Coprinus comatus|shaggy ink caps]] attack nematodes]]
[[File:A juvenile root-knot nematode (Meloidogyne incognita) penetrates a tomato root - USDA-ARS.jpg|thumb|upright|Juvenile root-knot nematode (''[[Meloidogyne incognita]]'') penetrating a tomato root]]
Some nematophagous fungi produce toxic substances which immobilise nemotodes. For example, the hypha of the [[Coprinus comatus|shaggy ink cap]] (''Coprinus comatus'') attacks the free-living soil nematode ''[[Panagrellus redivivus]]'' with a structure known as a spiny ball; this is used to damage the nematode cuticle to enable immobilisation, after which the hypha pierces the skin and digests the contents.<ref></ref>
Most endoparasitic fungi have spores that are attracted to soil nematodes and tend to congregate in the mouth region. Having penetrated the cuticle, the hyphae grow throughout the nematode, absorbing its tissues. Escape tubes emerge from these and grow through the cuticle, and in due course, further motile spores exit through these, ready to infect other nematodes. In other species of fungi, it is [[Conidium|conidia]] rather than spores which are encountered by the nematode and infect it in a similar way.<ref>Liquid error: wrong number of arguments (1 for 2)</ref> In the case of ''[[Harposporium anguillulae]]'', the sickle-shaped conidia are ingested by the nematode and lodge in the oesophagus or gut from where they invade the tissues.<ref></ref>
In egg parasitic species, the hypha flattens itself against the egg, the appearance of [[appressoria]] indicating that infection is about to take place or has already done so. The hypha then pierces the egg and devours the developing juvenile nematode before producing conidiophores and growing on towards nearby eggs.<ref></ref>
==Biological control==
Some species of nematophagous fungi are being investigated for use in [[biological pest control]]. ''[[Purpureocillium|Purpureocillium lilacinum]]'', for example, infests the plant-parasitic ''[[Meloidogyne incognita]]'', which attacks the roots of many cultivated plants. Trials have provided varying results, with some strains being aggressive and others less pathogenic, and some strains that appeared promising in the lab proved ineffective in the field.<ref></ref> ''Arthrobotrys dactyloides'' shows promise at controlling the cosmopolitan plant-parasitic [[root-knot nematode]] ''[[Meloidogyne javanica]]''.
== References ==
==Bibliography==
*
[[Category:Carnivorous fungi]]
[[Category:Fungal pest control agents]]
==種類==
依照不同的取食方式，分成5大類:
1.捕捉/獵食性(Nematode-trapping /predatory fungi): 菌絲主要存在土壤或植物殘體，利用特殊構造捕捉線蟲，包含以下6種捕捉構造:
"黏著性網(Adhesive nets)":有黏性，但無法收縮。當線蟲接觸到菌網時，菌網分泌出大量黏液捕獲線蟲，菌絲侵入線蟲並形成球形結構，然後產生大量的菌絲填滿蟲體腔，逐漸耗盡蟲內的營養。例如: ''Arthrobotrys''
<ref>Liquid error: wrong number of arguments (1 for 2)</ref>
"非收縮環(Non-constricting or detachable rings)":可和菌絲一起脫落。環狀結構由三個細胞融合而成，此環能分泌黏性物質，其柄長而細弱，線蟲一旦套住後，易被折斷而脫落，並被線蟲帶走，仍保有發芽的能力。同一菌絲通常有非收縮環結構者必有黏著球結構並存。例如: ''Monacrosporium
''
"收縮環(Constricting rings)":無法隨菌絲脫落。為一個三細胞環結構，其柄短而結實，當線蟲穿過環時，菌環細胞的直徑會急劇變大，長度縮短，內徑縮小，線蟲被緊緊收縮在菌環中，麻痺而死亡，菌絲穿入線蟲並大量產生。<ref>Liquid error: wrong number of arguments (1 for 2)</ref>
"黏著球(Sticky (adhesive) knobs)":無法隨菌絲脫落。從菌絲的分支頂端長出之特化膨大具有黏性的菌球。黏性物質在球的表面形成一層薄層，線蟲先黏到一個球上，在線蟲掙扎過程中會觸碰到更多的黏性菌球並被緊緊困住，菌球上長出菌絲穿入線蟲體內形成球狀體，再從此球上長出大量菌絲充滿蟲體 ，例如: ''Monacrosporium'' 、擔子菌中''Hohenbuehelia'' (亞側耳) 和''Resupinatus'' (伏褶菌)，可在木頭內形成滴漏狀(hour-glasses)的黏性菌球
"黏著性分支(Sticky (adhesive) branches) "
"黏性菌絲(Sticky (adhesive) hyphae)":主要為接合菌中的捕蟲黴菌門，菌絲產生黏性物質覆蓋在菌絲表面而有黏性，亦可捕捉其他原生生物，無法經由人工培養。這類構造捕蟲能力較強，當線蟲接觸黏性菌絲後，儘管只有一個接觸點，線蟲也會立即被黏住而失去活動力，黏性菌絲即刻產生侵染菌絲從接觸點侵入蟲體吸收營養，殺死蟲體。例如: ''Acaulopage''
2.內寄生性(Endoparasitic): 此類菌主要以線蟲為營養為一來源 (絕對寄生性)，以孢子感染蟲體。菌體主要存在於線蟲寄主，並不會在土壤內長距離延伸，產生的孢子經由體表黏附(Attach to nematode cuticle)和攝入線蟲(Ingested by nematode)來感染線蟲，孢子在線蟲體內發芽後穿透至線蟲體外，並於線蟲體外產生孢子。
"Attach to nematode cuticle":又分為兩種
可藉由游走孢子(motile spores)內寄生，例如: ''Catenaria''(Chytridiomycota)、''Myzocytium'' (Oomycota)、''Lagenidium'' (卵菌)
可藉由黏性孢子(adhesive spores)內寄生，例如: Haptocillium( sticky conidia)、Ｈirsutella (Ascomycota)用Adhesive conidia (spores)
"Ingested by nematode":藉由吞食性孢子(ingested spore)，有不同形狀，可被線蟲取食進入腸道中，卡在體內發芽，形成孢子。例如: ''Harposporium anguillulae<ref>Liquid error: wrong number of arguments (1 for 2)</ref>'' (Ascomycota) (anamorph用non-adhesive conidia被線蟲攝入)
3.Injected spores:彈射孢子感染線蟲，為絕對寄生。大多數為卵菌，少數為接合菌。死後的線蟲直接產生孢子囊梗(螺旋狀扭曲)，彈射出孢子感染線蟲。若孢子無遇到寄主，會直接在基質上形成厚膜孢子，等待機會感染。例如: ''Haptoglossa mirabilis'' (Oomycota)
4. Parasites of eggs or cysts:寄生在線蟲的不動結構，卵(eggs)<ref></ref>或胞囊(cysts)<ref>Liquid error: wrong number of arguments (1 for 2)</ref>。為伺機性的(Opportunistic)本身殘存於土壤環境中，行腐生 ，非絕對寄生，並無特化的感染構造，主要以菌絲感染。例如: ''Pochonia chlamydosporia'' (Anamorph)、''Metacordyceps chlamydosporia''(Teleomorph 、Clavicipitaceae 麥角菌科)、''Purpureocillium lilacinus''
除了''Nematophthora gynophilis'' (oomycetes)以游走孢子(zoospore)感染線蟲的胞囊。
5. Kill by toxins:分泌毒素毒殺線蟲。例如: 側耳屬 (''Pleurotus<ref>Liquid error: wrong number of arguments (1 for 2)</ref>'')特化細胞在菌絲周圍形成滴狀毒素，使線蟲麻痺死亡；
薄殼菌屬 （''Hyphoderma''）屬於擔子菌亞門皮殼菌Corticiaceae目之種類，其對線蟲有捕捉及毒殺現象
"捕捉": 有些種可以以一室或二室之冠囊体<ref></ref> （stephanocyst，從菌絲上側生出或直接從孢子產生的球形細胞，其基部環生一圈小刺結構）捕捉、黏著松材線蟲之後侵入寄生並加以毀滅
"毒殺": 有些種則細胞質所具之毒性物質（毒素），當細胞質被松材線蟲取食後，即可將其毒殺，再產生短側枝侵入線蟲體腔，破壞其器官、組織，並將其分解、吸收其組成分
==生態學==
"捕捉/獵食性(Nematode-trapping /predatory fungi)真菌":
1.主要是以腐生營養，以線蟲來補充其N源
2.大部分種類之捕捉構造需要有線蟲存在時產生 (受線蟲分泌物的刺激)，生物防治效率不高，因為菌種在土壤中易被稀釋，需線蟲保持其高濃度的菌量。
3.捕捉性真菌並無寄主之偏好
4. Adhesive nets、Non-constricting or detachable rings、Constricting rings、Sticky (adhesive) knobs、Sticky (adhesive) branches大多存於高等真菌中無性繁殖的不完全菌
5. 6種捕捉構造(除constricting rings外)皆為adhesive，黏著性
6. 感染為irreversible (不可逆的)，一旦啟動了感染，縱使線蟲掙脫，捕捉構造仍會黏附在線蟲身上，並持續感染之
7. 許多nematode-trapping fungi之有性時期為盤菌之Orbiliales目的種類，子實體小，大量聚集透明狀且有不同顏色
"內寄生性(Endoparasitic)真菌"生態學:
1.有些內寄生菌有寄主之偏好性，如寄生性線蟲的口器就不適合取食Harposporium之孢子，所以無法感染
2.所以屬於"Ingested by nematode"之種類無法用於生物防治寄生性線蟲， "Attach to nematode cuticle"的種類則可
==多樣性==
在世界各地的各種棲息地和氣候中都發現了食線蟲真菌，但很少來自極端環境。研究最多的是攻擊農業生產線蟲的物種，但仍有許多物種未被探討。Orbilia的有性階段發生在陸地或淡水中的腐爛木材上，而無性階段發生在海洋，淡水和陸地棲息地。''Arthrobotrys dactyloides''是在鹹水中發現的第一個物種，而亦在紅樹林中發現了其他物種。
==生物防治==
1. Duddingtonia flagrans(為Orbiliales中的捕食性真菌):用於生物防治動物線蟲病害，無法殺死草食動物體內之線蟲 (主要是殺死糞便內之線蟲)，將孢子餵食動物，孢子會在糞便中發芽生長，產生捕捉構造捕捉線蟲，草上的線蟲擴散率降低，草食動物不易吃到線蟲，僅是防止二次感染，殺死體內已存有的線蟲，所以仍要配合驅蟲藥劑服用。防治時，必須要持續餵食真菌孢子才能達到治療效果
2.植物寄生性線蟲具有針狀口器，無吞噬能力，無法用內寄生真菌的攝入線蟲(Ingested by nematode)途徑來感染線蟲，但可用體表黏附(Attach to nematode cuticle)方式。但對於腐生性線蟲的話，其吞噬孢子的能力較佳，則用內寄生真菌的攝入線蟲(Ingested by nematode)途徑來感染線蟲
3.''Purpureocillium lilacinus''<ref></ref>可做為微生物防治劑，用其菌絲感染線蟲的卵
4薄殼菌屬 （''Hyphoderma''）此等菌類之生態習性和松材線蟲接近，對松樹又不具病原性，故具防治松材線蟲潛能。由於冠囊體表面之黏液醣蛋白，和松材線蟲体表之醣蛋白的互補作用，而產生專一性之辨識作用
[[Image:20100814 175958 FungusOnDeadnematode HarposporiumAnguillulae.jpg|thumb|right|A dead nematode with ''[[Harposporium anguillulae]]'' growing out of it. Numbered ticks are 122 µm apart.]]
[[Image:20100814 180201 FungusOnDeadnematode HarposporiumAnguillulae.jpg|thumb|right|A closer look at ''H. anguillulae'' fungi from the previous image. Numbered ticks are 20 µm apart.]]
[[Image:20100828 005957 Fungus.jpg|thumb|right|A fungus of the genus ''[[Arthrobotrys]]'', showing adhesive nets which it uses to trap nematodes. Numbered ticks are 122 µm apart.]]
'''Nematophagous fungi''' are [[carnivorous fungus|carnivorous fungi]] specialized in trapping and digesting [[nematode]]s. Around 160 species are known. There exist both species that live inside the nematodes from the beginning and others that catch them, mostly with glue traps or in rings, some of which constrict on contact. Some species possess both types of traps. Another technique is to stun the nematodes using toxins, which is a method employed by ''[[Coprinus comatus]]'', ''[[Stropharia rugosoannulata]]'', and the family [[Pleurotaceae]].<ref name="thorn00"></ref> The habit of feeding on nematodes has arisen many times among fungi, as is demonstrated by the fact that nematophagous species are found in all major fungal groups.<ref></ref> Nematophagous fungi can be useful in controlling those nematodes that eat crops. ''[[Purpureocillium]]'', for example, can be used as a bio-[[nematicide]].
==Types==
Fungi that feed on nematodes (as the most abundant and convenient prey species) mostly live in nitrogen-deficient habitats.<ref name=Hsueh></ref> These fungi can be divided into four main groups according to the methods they use to catch their prey. Some use a mechanical means, an adhesive or a mechanical [[hypha]]l trap. Some produce a toxin and use it to immobilise the nematode. Some are [[Parasitism|parasitic]], using their spores to gain entry into their prey, and some are egg parasites, inserting their hyphal tips into the eggs or cysts, or into females before the eggs are deposited.
==Diversity==
Nematophagous fungi have been found throughout the world in a wide range of habitats and climates, but few from extreme environments. Most studied have been the species that attack the nematodes of interest to farmers, horticulturists and foresters, but there are large numbers of species as yet undescribed. The sexual stage of ''[[Orbilia]]'' occurs on rotting wood on land or in fresh water, while the asexual stage occurs in marine, fresh water and terrestrial habitats. ''[[Arthrobotrys dactyloides]]'' was the first species to be discovered in [[brackish water]], and other species have been found on [[mangrove]]s.
==Ecology==
Nematode-trapping fungi are mostly concentrated in the upper part of the soil, in [[pasture]]s, [[leaf litter]], [[mangrove]]s and certain shallow aquatic habitats. They employ techniques such as adhesive hyphal strands, adhesive knobs, adhesive nets formed from hyphal threads, loops of hyphae which tighten round any ensnared nematodes and non-constricting loops. When the nematode has been restrained, the hyphae penetrate the cuticle and the internal tissues of the nematode are devoured.
It has been found that ''[[ Arthrobotrys oligospora]]'', a net-building species of fungus, can detect the presence of nematodes nearby in the soil and only builds its snares when they are present. This is presumably because building the net is a highly energy-consuming process; the fungus is alerted to the presence of the nematode by detecting the [[pheromone]]s, such as [[ascaroside]]s, with which the worms communicate. The fungus takes active steps to attract its prey by producing olfactory cues that mimic those used by the worm to find food and attract mates.<ref name=Hsueh/> ''Arthrobotrys dactyloides '' is a species that employs a loop of hypha to catch nematodes; when one tries to pass through the ring, the loop constricts with great rapidity, trapping the prey.
[[File:Schopftintling-Coprinus-comatus.jpg||upright|thumb|The hyphae of [[Coprinus comatus|shaggy ink caps]] attack nematodes]]
[[File:A juvenile root-knot nematode (Meloidogyne incognita) penetrates a tomato root - USDA-ARS.jpg|thumb|upright|Juvenile root-knot nematode (''[[Meloidogyne incognita]]'') penetrating a tomato root]]
Some nematophagous fungi produce toxic substances which immobilise nemotodes. For example, the hypha of the [[Coprinus comatus|shaggy ink cap]] (''Coprinus comatus'') attacks the free-living soil nematode ''[[Panagrellus redivivus]]'' with a structure known as a spiny ball; this is used to damage the nematode cuticle to enable immobilisation, after which the hypha pierces the skin and digests the contents.<ref></ref>
Most endoparasitic fungi have spores that are attracted to soil nematodes and tend to congregate in the mouth region. Having penetrated the cuticle, the hyphae grow throughout the nematode, absorbing its tissues. Escape tubes emerge from these and grow through the cuticle, and in due course, further motile spores exit through these, ready to infect other nematodes. In other species of fungi, it is [[Conidium|conidia]] rather than spores which are encountered by the nematode and infect it in a similar way.<ref>Liquid error: wrong number of arguments (1 for 2)</ref> In the case of ''[[Harposporium anguillulae]]'', the sickle-shaped conidia are ingested by the nematode and lodge in the oesophagus or gut from where they invade the tissues.<ref></ref>
In egg parasitic species, the hypha flattens itself against the egg, the appearance of [[appressoria]] indicating that infection is about to take place or has already done so. The hypha then pierces the egg and devours the developing juvenile nematode before producing conidiophores and growing on towards nearby eggs.<ref></ref>
==Biological control==
Some species of nematophagous fungi are being investigated for use in [[biological pest control]]. ''[[Purpureocillium|Purpureocillium lilacinum]]'', for example, infests the plant-parasitic ''[[Meloidogyne incognita]]'', which attacks the roots of many cultivated plants. Trials have provided varying results, with some strains being aggressive and others less pathogenic, and some strains that appeared promising in the lab proved ineffective in the field.<ref></ref> ''Arthrobotrys dactyloides'' shows promise at controlling the cosmopolitan plant-parasitic [[root-knot nematode]] ''[[Meloidogyne javanica]]''.
== References ==
==Bibliography==
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[[Category:Carnivorous fungi]]
[[Category:Fungal pest control agents]]
http://bit.ly/2QS2e84
