, …
, in

Encyclopedia of Inland Waters, 2009


Aquatic fungi
are microscopic organisms with more often than not mycelial growth and hyphae developing on or within their typically submerged organic substrates of institute or animal origin. Resident aquatic fungi are able to complete their life cycle in freshwaters and often have special adaptations for growth, sporulation, and dispersal in aquatic environments. A number of so-chosen transient fungi that are diddled in from terrestrial ecosystems are regularly reported from freshwaters, but they may or may not exist metabolically active under submerged atmospheric condition. Emergent macrophytes ( thousand., cattail or reed stands) also harbor terrestrial fungi, especially during the aeriform standing-dead decomposition stage. These fungal assemblages volition also be considered hither considering of their crucial importance in decomposing plant detritus in wetlands and lake littoral zones. Freshwater fungi are rather difficult to detect and study due to unusual grapheme of the habitat and the intimate association of fungal hyphae with the substrate they colonize. As a result, they were often overlooked by both aquatic ecologists and mycologists akin. Since the 1940s, some interest in the systematics and evolutionary relationships among these fungi has emerged. Furthermore, development and awarding of quantitative methods within the final ii decades have established that fungi play a primal role in the decomposition of plant litter in freshwater environments and are important mediators of energy and nutrient transfer to college trophic levels (e.chiliad., shredding invertebrates). Even though some freshwater fungi or fungus-like organisms are economically or ecologically of import parasites of aquatic animals and plants, almost freshwater fungi depend on dead fibroid particulate organic matter (CPOM), mostly plant litter, as their main source of energy and nutrients. This dead constitute material may be of autochthonous (e.g., submerged or emergent macrophytes) or of allochthonous origin (leaf litter and wood from the riparian zone). This chapter will focus on fungi associated with plant litter in two freshwater ecosystems that have received the most attention: streams and wetlands or marshes. Since fungal action and fungi-mediated processes differ between the lotic and lentic ecosystems, they will be discussed separately.

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Fungi and Chytrids

Van den Wyngaert
, in

Reference Module in Globe Systems and Environmental Sciences, 2022

What are aquatic fungi?—Functional and taxonomic nomenclature

One of the showtime records of aquatic “true fungi” dates back to the mid-19th century when Braun discovered parasitic fungi on light-green algae (Braun 1856). He named these fungi “chytridien” (east.g., chytrids) which subsequently became the phylum Chytridiomycota (Hibbett et al., 2007
). Collectively,
aquatic fungi
were called Phycomycetes (algal-fungi) (

Sparrow, 1960) (Table one). As many Phycomycetes share the morphological trait of flagellated zoospores which are the principal agents of dispersal and infection/colonization of substrates in water, they have also been classified under the term “zoosporic fungi.” Since Braun’s first observations of parasitic chytrids on algae, many more species have been discovered which interact with a large multifariousness of living organisms and organic substrates (Sparrow, 1960). Chytrids have been institute to display a continuum of consumer strategies ranging from obligate parasites to saprophytes (Frenken et al., 2017;
Sparrow, 1960). There are even zoosporic fungi (e.grand., Rozellomycota) that parasitize other parasitic chytrids of phytoplankton (Amble, 1969). With the advent of DNA-based taxonomy, information technology is now well established that zoosporic fungi are a polyphyletic group including true zoosporic fungal lineages (Kingdom Fungi) and pseudofungal lineages (Kingdom Chromista). This indicates that shared functional characteristics such as osmotrophy and certain growth habits arose through convergent evolution. Chytrids, which currently embrace phyla Chytridiomycota, Blastocladiomycota and Neocallimastigomycota, represent the largest group of true zoosporic fungi in freshwater lakes.

Tabular array 1.
Functional and taxonomic classification of aquatic fungi.

Previous classification Morpho-functional nomenclature Dna based nomenclature Phyla containing aquatic lineages Representative genera Trophic interactions
True Fungi Ascomycota

Aquatic Hyphomycetes/Filamentous fungi

Aero-aquatic Hyphomycetes/Filamentous fungi

Yeast (Y)

Ascomycota Tetracladium


Crucella Debaryomyces
Metschnikowia (Y)
Saprophytic on decaying
leaves and submerged wood
Parasitic on other fungi
Saprophytic and symbiotic?
Parasitic on zooplankton
Basidiomycota Basidiomycota Rhodotorula (Y)

Cryptococcus (Y)
gut endosymbionts?
Mutualistic interaction with algae/opportunistic man pathogen
Zygomycota Trichomycetes/Filamentous fungi Kickxellomycota Harpella Endosymbionts freshwater arthropods
Zoopagomycota Acaulopage

Predators of amoeba
Predators of rotifers
Filamentous fungi Basidiobolomycota Basidiobolus Saprotrophic and parasitic on amphibians
Phycomycetes Zoosporic fungi Olpidiomycota Olpidium Parasitic on plants, animals, protists, and fungi
Chytridiomycota Zygophlyctis Parasitic on diatoms
Rhizophydium Parasitic on algae Saprotrophic on pollen/
Rhizoclosmatium Saprotrophic on chitinous substrates
Batrachochytrium Parasitic on invertebrates
Monoblepharomycota Monoblepharis Saprotrophic on water-logged twigs
Neocallimastigomycota Piromyces Anaerobic symbiont
Blastocladiomycota Blastocladiella

Saprotrophic on institute debris
Parasitic on algae
Aphelidiomycota Amoeboaphelidium Parasitic on algae
Rozellomycota Rozella Parasitic on chytrids and oomycetes
Pseudo-Fungi Oomycota Phytium


Saprotrophic on pollen
Parasitic on diatoms
Parasitic on fish/fish eggs
Hyphochytriomycota Hyphochytrium Saprotrophic on pollen
Parasitic on algae and resting spores of oomycetes
Labyrinthulomycota Labyrinthula Saprophytic and opportunistic pathogens of algae

Dna based nomenclature based on
Tedersoo et al., 2018
Wijayawardene et al., 2018.

A second of import ecological group of aquatic fungi was discovered by Ingold in the mid-20th century, who observed feature fungal spores associated with decaying leaves in streams, and which he defined as aquatic hyphomycetes (Ingold, 1942). These are filamentous fungi that reproduce mainly asexually and in addition to leaves in streams, are constitute on decomposable macrophytes or driftwood in running river systems, wetlands or littoral of lakes. The bulk of them belong to Ascomycota and few to Basidiomycota.

The Ascomycota and Basidiomycota also comprise unicellular yeasts which are ofttimes plant in the pelagic zone of lakes as free-floating cells, attached to substrates, or within fauna hosts (Buzzini et al., 2017). Trichomycetes are another diverse ecological group of aquatic fungi that are obligate endosymbionts in the gut of many aquatic insects. They used to exist a member of the phylum Zygomycota; nevertheless, molecular identification methods take shown that some Trichomycete species are more related to Protozoa than to true fungi.

There is not e’er a clear stardom between aquatic and terrestrial fungi. Whereas some aquatic fungi have an obligate aquatic lifestyle and consummate their whole life cycle in water (residents), others accept both an aquatic and terrestrial life cycle and are and so called aero-aquatic fungi (Chauvet et al., 2016). Finally, terrestrial fungi may occur in h2o, merely by being washed or diddled in, without showing whatsoever activity in water (transients). Information technology remains a claiming to precisely characterize where species fall along this slope of adaptation to aquatic habitats (Shearer et al., 2007).

Fungal adaptations to an aquatic lifestyle

Aquatic fungi
have evolved increasing size, complexity, and metabolic functioning from small intracellular fungal parasites upward to larger mycelian networks of filamentous fungi capable of decomposing big refractory organic textile.

Fig. i
displays a diversity of dispersal and vegetative structures of aquatic fungi with their corresponding size ranges. Macroscopic fungal structures, i.e., large fruit bodies, are virtually completely absent in aquatic habitats (but see
Psathyrella aquatica, the first fungi discovered fruiting underwater, (Frank et al., 2010)).

Fig. 1

Fig. one.
Relative sizes of various dispersal and vegetative structures of aquatic fungi.

Images for chytrid zoospores and Aphelidiomycota courtesy of Grand. Seto, Academy of Michigan, US. Image of yeast cells of
Dirkmeia churashimaensis
courtesy of B. Hassett,
The Arctic university of Norway, Norway. Image of
Zoophagus pectospora
courtesy of W. Davies, United States Department of Agronomics, US. Image of dispersal spore of aquatic hyphomycete courtesy of C. Wurzbacher, Technical University of Munich, Germany.

Zoosporic true fungi which are ancient in term of evolution, since they diverged from the other fungal lineages ca. 750 million years ago (Medina and Buchler, 2020), take most likely an aquatic origin. Their dispersal stages show main adaptations to an aquatic lifestyle in the form of flagellated motile zoospores. Contrary to heterotrophic nanoflagellates, fungal zoospores have unique characteristics, such as a single posterior whiplash flagellum and a large refractive lipid globule that serves equally an free energy reserve for fueling active zoospore motion.

The recently discovered Aphelidiomycota, endoparasites of unicellular algae, have both amoeboid and flagellated dispersal stages (Karpov et al., 2014a). In contrast to other fungi that blot dissolved nutrients from the environment (osmotrophy), endoparasitic lineages Aphelidiomycota and Rozellomycota engulf the content of their host, like amoebae, and digest it in special vacuoles (phagocytosis). The vegetative structures of chytrids are called rhizoids, which are tiny root-like hyphae. Rhizoids ballast the chytrid to the substrate (or host) and excrete enzymes to break information technology downwardly (Powell, 2017). Chytrids tin modify their rhizoidal structure in response to nutrient availability in a similar manner as filamentous fungi (Laundon et al., 2020).

Aquatic hyphomycetes well-nigh probably evolved from terrestrial fungi and secondary morphological adaptations to colonize aquatic environments take evolved independently in multiple lineages (Baschien et al., 2013). The asexual dispersal stages of aquatic hyphomycetes are typically tetraradiate or sigmoidal shaped and take viscid sheaths that facilitate their attachment nether turbulent conditions to submerged substrates.

The size difference between the rhizoidal structures of chytrids and hyphal structures of aquatic hyphomycetes implies ecological niche differences between both fungal groups.
Wurzbacher et al. (2016)
formulated this as the “morphotype hypothesis,” i.e., zoosporic fungi become increasingly more of import on fine particulate organic matter (FPOM) such every bit pollen grains or algae, whereas aquatic hyphomycetes tend to colonize proportionally more the larger coarse particulate organic matter (CPOM).

Some members of Ascomycota, Basidiomycota and Zygomycota accept developed trapping structures, such every bit adhesive spores, hyphae or rings to capture water-inhabiting micro invertebrates, like nematodes, rotifers or amoeba (Corsaro et al., 2018;
Davis et al., 2019;
Karling, 1936). After they have captured their prey, hyphae penetrate and digest the prey tissues. Most single celled yeasts represent fungal lineages where the ancestral hyphal growth form was abandoned. Nevertheless, some yeast species still produce pseudo-hyphae or are dimorphic, i.e., they grow as single celled yeast or form true hyphae depending on environmental conditions (Harris, 2011). The diverse ecological role of yeast in aquatic ecosystems is still poorly understood (Wurzbacher et al., 2010). Yeast accept been identified as members of the gut microbiota and parasites in aquatic invertebrates and animals. Equally saprophytes, consuming dissolved organic matter (DOM), they potentially share ecological niches with heterotrophic leaner and compete for nutrients. Mutualistic relationships have been documented betwixt the alga
Euglena mutabilis
and yeast of the genus
Cryptococcus, which allow both species to colonize together farthermost acidic and heavy metal polluted habitats (Nakatsu and Hutchinson, 1988). Yeast display a wide diversity of extracellular enzymatic activities that tin can promote algae and found growth by increasing food availability and assimilation (Gomes et al., 2015).

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Pathogens of Insects

Brian A.
, in

Encyclopedia of Insects (Second Edition), 2009

Aquatic Fungi

Aquatic fungi
of two types that attack musquito larvae have received considerable study: species of

(class Chytridiomycetes: lodge Blastocladiales) and
Lagenidium giganteum
(class Oomycetes: order Lagenidiales).

The genus
comprises over 80 species of obligately parasitic fungi that have a complex life cycle involving an alternation of sexual (gametophytic) and asexual (sporophytic) generations. The sexual stage parasitizes a microcrustacean host, typically a copepod, whereas the asexual generation develops, with rare exception, in mosquito larvae. In the life cycle, a biflagellate zygospore invades the hemocoel of a mosquito larva, where information technology produces a sporophyte that colonizes the body and forms resistant sporangia. The larva dies and after the sporangia undergo meiosis, producing uniflagellate meiospores that invade the hemocoel of a copepod host, where a gametophyte develops. At maturation, the gametophyte cleaves, forming thousands of uniflagellate gametes. Cleavage results in death of the copepod and escape of the gametes, which complete the life cycle by fusing to biflagellate zygospores, which then seek out another mosquito host. The life cycles of these fungi are highly adapted to those of their hosts. Moreover, as obligate parasites these fungi are very fastidious in their nutritional requirements, and as a upshot no species of
has been cultured
in vitro.

Coelomomyces, the largest genus of insect-parasitic fungi, has been reported worldwide from numerous musquito species, many of which are vectors of of import diseases such as malaria and filiariasis. In some of these species,
Anopheles gambiae
in Africa, for example, epizootics acquired in some areas by
impale greater than 95% of the larval populations. Such epizootics led to efforts to develop several species every bit biological control agents. For several reasons, still, these efforts were discontinued. I important gene was the discovery that the life cycle requires a second host for completion. Also contributing were the inability to culture these fungi
in vitro
and the development of Bti as a bacterial larvicide for mosquitoes.

Although information technology is unlikely that
fungi will be developed as biological control agents, interest remains in developing
L. giganteum. This oomycete mucus is hands cultured on artificial media and does not crave an alternate host. In the life cycle, a motile zoospore invades a mosquito larva through the cuticle. One time within the hemocoel, the fungus colonizes the body over a period of 2–3 days, producing an all-encompassing mycelium consisting largely of nonseptate hyphae. Toward the end of growth, the hyphae become septate, and out of each segment an exit tube forms which grows back out through the cuticle and forms zoosporangia at the tip. Zoospores quickly differentiate in these, exiting through an apical pore to seek out a new substrate. In improver to this asexual cycle, thick-walled resistant sexual oospores can be formed in the mosquito cadaver.

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URL: discipline/article/pii/B9780123741448002022

Diagnosis of Parasitic and Nonparasitic Diseases

, in

Love apple Diseases (Second Edition), 2012

Olpidium brassicae

This aquatic fungus is not thought pathogenic on love apple; however, it is and then on seedlings of tobacco which is also a solanaceous plant. Yet information technology is not uncommon to find its sporangia and chlamydospores, or ‘resting spores’ in the cells of the epidermis and cortex of tomato roots (Photo


whether grown in soil or soil-less. The quantities found in the soil-less ingather roots are sometimes very large and question the function of this parasitic root mucus. Is it a simple biomarker of roots during decomposition or does it influence senescence? Note that it is also the vector of two very damaging viral diseases on salads: big vein disease and orange blotch.

Environmental conditions including temperature and oxygenation of soil, the substrate or nutrient solution, and peculiarly the root condition, certainly influence its behaviour. This fungus is well adapted to aquatic life and has, equally

spp. and other
aquatic fungi, mobile zoospores allowing it to spread easily in water and in the nutrient solutions of soil-less culture.

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URL: discipline/article/pii/B9780123877376500029

Spore Product, Discharge, and Dispersal

Nicholas P.
, in

The Fungi (3rd Edition), 2016

Non-Motile Aquatic Spores

Spores of
aquatic fungi
engaged in leaf decomposition are plentiful in calcareous streams. These are conidia of ascomycetes, and a smaller number of basidiomycetes, called Ingoldian fungi after C. T. Ingold (1905–2010), who discovered them in the 1930s. Information technology has been suggested that some of the Ingoldian fungi are endophytes and that their colonies are dispersed past leaf abscission. Ingoldian spores are striking for their elaborate shapes, including stars with four limbs continued to a primal hub (tetraradiate conidia), crescents, sigmoids, commas, and miniature cloves (

Effigy iii.21). They grade at the tips of conidiophores that develop at the surface of leaves and become full-bodied in bubbles of white foam that accumulate effectually rocks and fallen logs obstructing water catamenia. Collection of foam samples provides a convenient way to study these fungi and pure cultures can be obtained by harvesting spores from leaves after a brusk incubation in the lab.

Figure three.21.
Multifariousness of conidia produced by Ingoldian fungi in freshwater habitats.

Source: Webster, J., Weber, R.W.South., 2007. Introduction to Fungi, third edition. Cambridge University Press.

Spore morphology is no more important in determining sedimentation rate in h2o than information technology is for spores dispersed in air. The high viscosity of water relative to air slows the sedimentation rate of spores from millimetres
per second
to millimetres
per infinitesimal, but most experiments testify that conidia with appendages fall through the h2o column at the same speed as more compact spores. Indeed, one experiment showed that intact spores of marine fungi settled faster than spores whose appendages had been disrupted past sonication. The unusual shapes of aquatic spores require an alternative explanation.

The most compelling answer is that the broader span of spores with unusual shapes increases the probability that they volition collide with submerged institute materials. The largest conidia produced by the Ingoldian
Brachiosphaera tropicalis
have an effective diameter of 0.four
mm (Figure 3.1f). A spherical spore of this bore would weigh approximately xl
μg; the tetraradiate spore with a fundamental hub and slender arms is 400 times lighter, producing a like probability of hitting a leaf fragment nonetheless saving a considerable investment in cytoplasm. This calculation is a little simplistic because the spherical spore might reduce its volume of active cytoplasm past expanding a large fluid-filled vacuole. Besides, the expanse of the tetraradiate spore is but xxx times less than the surface of the sphere, which means that the economy in prison cell wall product is more small than the potential reduction in cytoplasm. Nevertheless, the concept of the spore as a search vehicle probably explains the significance of the beautiful spore shapes in these fungi. The utility of the spore morphology with multiple appendages is evident from its convergent development in basidiospores of the marine wood-rotting basidiomycete
Nia vibrissa.

The extended shapes of these aquatic spores may confer other advantages. Experiments on tetraradiate conidia show that when one arm of a spore strikes a target, the spore pivots around this signal of attachment assuasive the fungus to make a stable 3-point landing. Leafage colonization begins when the tips of the arms cement themselves to the surface and slender hyphae abound from the triangle of contacts. Enhanced dispersal in surface films is another possible do good of this spore morphology and helps explain the concentration of spores in foam. It has been suggested that spores trapped in cream may get airborne as the bubbling collapse. This would explain how some of these aquatic fungi establish themselves equally endophytes in plants growing higher up the water.

A different adaptation is observed in aeroaquatic conidia that course at the air–water interface in stagnant ponds. These spores develop by helical growth of hyphae to course barrels with an air bubble trapped in the centre. Dispersal occurs by floating on the surface of the h2o and these fungi colonize leaves and decaying woods. Many other fungi that grow on plant debris in aquatic environments do not evidence any obvious morphological adaptations to their habitats.

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A Perspective on Pathogens equally Biological Control Agents for Insect Pests

, in

Handbook of Biological Command, 1999

Coelomomyces and Lagenidium

Ii types of
aquatic fungi
that attack mosquito larvae take been studied for use every bit biological control agents, species of

(class Chytridiomycetes; order Blastocladiales) and
Lagenidium giganteum
(course Oomycetes; order Lagenidiales).

The genus
is composed of over 70 species of obligately parasitic fungi that have a complex life cycle involving an alternation of sexual (gametophytic) and asexual (sporophytic) generations (Couch & Banal, 1985;
Whisler, 1985). In all species studied to appointment, the sexual phase parasitizes a microcrustacean host, typically a copepod, whereas the asexual generation develops, with rare exception, in mosquito larvae. In the life bicycle, a biflagellate zygospore invades the hemocoel of a mosquito larva where it produces a sporophyte that colonizes the body and forms resistant sporangia. The larva dies and after the sporangia undergo meiosis, producing uniflagellate meiospores that invade the hemocoel of a copepod host, where a gametophyte develops. At maturation, the gametophyte cleaves, forming thousands of uniflagellate gametes.
Cleavage results in death of the copepod and in escape of the gametes, which fuse and grade biflagellate zygospores that seek out some other mosquito host, completing the life wheel. The life cycles of these fungi are highly adjusted to those of their hosts. Moreover, as obligate parasites these fungi are very fastidious in their nutritional requirements, and equally a result no species of
has been cultured
in vitro.

is the largest genus of insect-parasitic fungi, and has been reported worldwide from numerous mosquito species, many of which are vectors of important diseases such as malaria and filiariasis. In some of these species,
Anopheles gambiae
in Africa for case, epizootics caused by
kill greater than 95% of the larval populations in some areas (Couch & Umphlett, 1963;
Chapman, 1985). Such epizootics led to efforts to develop several species every bit biological control agents during the past three decades (Federici, 1981). Even so, these efforts have largely been discontinued due to the discovery that the life bike required a second host for completion, the disability to culture these fungi
in vitro,
and the development of B.t.i. every bit a bacterial larvicide for mosquitoes.

Though the difficulties encountered with
arrive unlikely this fungus will ever be developed as a biological control agent, there is yet considerable interest in
Lagenidium giganteum.
This oomycete fungus has 2 important advantages over
it is easily cultured on artificial media and information technology does not require an alternate host (Federici, 1981). In the life cycle, a motile zoospore invades a mosquito larva through the cuticle. Once within the hemocoel, the mucus colonizes the torso over a period of 2 to 3 days, producing an extensive mycelium consisting largely of nonseptate hyphae. Toward the end of growth, the hyphae become septate, and out of each segment an exit tube forms that grows back out through the cuticle and forms zoosporangia at the tip. Zoospores quickly differentiate in these, exiting out through an apical pore to seek out a new substrate. In add-on to this asexual bicycle, thick-walled resistant sexual oospores tin can also exist formed within the mosquito cadaver.

Techniques accept been developed to produce both zoosporangia and oospores
in vitro,
and methods are currently being developed to alter existing applied science so that the mucus can be mass-produced. Several years of field trials in California and N Carolina take shown that the zoosporangia are too delicate for routine apply in operational control programs. The oospore, however, is quite stable though germination remains unpredictable. Nevertheless, field results betoken that germination of even a small percentage of oospores can result in the initiation of epizootics that atomic number 82 to flavor-long mosquito command (Kerwin & Washino, 1987). Although several technical issues related to mass product and formulation remain to be overcome,
L. giganteum
remains a promising candidate for successful commercial development. Its main advantage over B.t.i. is that if effective formulations tin can exist developed, information technology appears that in many habitats only a single application would be required, at most, per season. Even less frequent applications may be possible in some habitats because evidence suggests that the oospores can overwinter, initiating
epizootics the post-obit seasons. The extent to which this occurs and can exist relied on for effective mosquito control remains to exist determined.

A small biotechnology firm, AgraQuest of Sacramento, California, has begun producing a product based on
L. giganteum
with the trade proper name of Lagenex. The product has not been in use long enough to access either its operational efficacy or its commercial success.

In addition to
Fifty. giganteum,
the aquatic hyphomycete fungi
Culicinomyces clavosporus
Couch and
Tolypocladium cylindrosporum
have been considered for mosquito control (Federici, 1981;
Soares & Pinnock, 1984); however, high production costs, lack of articulate and toll-constructive control in the field, and the appearance of B.t.i. accept eliminated these fungi equally serious candidates for development equally microbial control agents.

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Fungi: Biomass, Product, and Sporulation of Aquatic Hyphomycetes

Keller F.
, in

Methods in Stream Ecology (2d Edition), 2007


Site Selection and General Considerations

Submerged decaying constitute litter that serves as substrate for
aquatic fungi
can be found in about all types of lotic habitats. Alternatively, found material introduced as leaf bags or packs tin can be used afterwards appropriate stream exposure. Collected leaf litter, woody substrates, expressionless macrophytes, or other organic materials are suitable for determination of fungal biomass and production since these assays are designed to target a wide group of fungi of mainly ascomycetous and basidiomycetous affinities (

Gessner and Newell 2002). If the objectives of the study also include estimation of sporulation rate and/or community structure of aquatic hyphomycetes, and then headwater streams may be the best option because of the greater abundance and diversity of these fungi in fast flowing well-aerated streams. Aquatic hyphomycetes tin also be plant in big rivers (e.g., seventh order;
et al.
) and specific objectives of the study (e.thousand., upshot of pollution, inorganic nutrients, pesticides, etc. on these fungi) may dictate the choice of site.

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Fungal Diversity

Nicholas P.
, in

The Fungi (Third Edition), 2016

Phylum Blastocladiomycota

Blastocladiomycota, along with the Chytridiomycota and Neocallimastigomycota, are
aquatic fungi
that produce flagellate zoospores. It is important to underscore the absence of flagella in the majority of the fungi. No flagella are produced by the Basidiomycota, Ascomycota, Glomeromycota, and filamentous zygomycetes. Some molecular phylogenetic studies have concluded that the loss of flagella occurred in one case in the fungal lineage, suggesting that there was a single common ancestor for all of the not-flagellate groups. Blastocladiomycota live in freshwater habitats, mud, and soil where they operate equally saprotrophs, decomposing plant and creature debris, or parasitize arthropods. Less than 200 species have been described.

species are saprotrophs that form separate haploid and diploid colonies with an unusual morphology. When
is grown on agar medium, it forms branched colonies of broad hyphae that lack septa. In liquid medium, or in samples of pond water, the hyphae are often stunted, producing brusk colonies attached to surfaces past a basal network of fine filaments referred to equally
rhizoids. Haploid and diploid colonies look the same, but when nutrients become limited, the hyphae stop extending and produce different types of reproductive structures at their tips (Figure ane.16). The diploid colony is called the
(drawing upon botanical classification). This forms two different types of sporangia:
meiosporangia. The zoosporangia release diploid zoospores. Each spore has a unmarried flagellum that pushes the spore through the water like a miniature tadpole. The single diploid nucleus in the spore contains a large nucleolus and is surrounded by a membrane-bound assemblage of ribosomes called the
nuclear cap. This spore structure is one of the distinguishing features of the Blastocladiomycota. The spores are chemotactic and direct their motion toward sources of dissolved amino acids. If they locate suitable food, the zoospores attach to the surface of the target, encyst, and class rhizoids that penetrate the underlying cloth. Branching hyphae of the new colony develop from the opposite side of the cyst and extend into the water. The importance of nutrient absorption by the rhizoids versus the hyphae is unclear, but may exist determined by the relative concentrations of nutrients in the food base and within the surrounding h2o. Hyphal cultures on solid medium probably function like the cultured mycelia of other fungi, with almost of the absorption of nutrients occurring at the hyphal apices every bit the colony periphery extends into fresh medium.

Figure 1.16.
Life bike of

Source: Lee, S.C., 2010. Microbiol. Mol. Biol. Rev. 74, 298–340.

The second type of sporangium, the meiosporangium, as well releases pond spores, simply these are formed by meiosis and give rise to haploid or
colonies. These colonies develop in the same mode every bit the sporophytes, but produce terminal structures, which wait like sporangia that release motile gametes rather than zoospores. The gamete-releasing structures are called
gametangia. In
Allomyces macrogynus, the male gametangia are formed at the ends of the hyphae, with the female gametangia directly behind them. The opposite system occurs in
Allomyces arbusculus. The male gametangia are coloured vivid orange with gamma-carotene. The female gametangia and gametes release a sexual attractant, or pheromone, chosen
to which the male gametes respond. After their release, male person gametes swarm around the female gametangia and fuse with the emerging female gametes. The fused gametes produce a biflagellate zygote that swims through the water until it locates a suitable food source and encysts. Upon germination, the cyst produces a new sporophyte colony and the life wheel processes tin exist repeated.

The zoospores of
Blastocladiella emersonii
have a very like construction to those of
Allomyces, but this fungus produces an ovoid thallus rather than the more than extended colony of branched hyphae characteristic of
Allomyces. Nutrient limitation triggers the transformation of the thallus into a sporangium from which zoospores are discharged into the h2o. Species of a third genus in the Blastocladiomycota,
Coelomomyces, are parasites of arthropods.
Coelomomyces psorophorae
has a complicated life cycle, reminiscent of the biological science of some rusts, which involves the infection of mosquito larvae and copepods. Prospects for the development of
species equally biocontrol agents against mosquito-borne infectious diseases seemed bright after the elucidation of its life bike in the 1970s, but attempts to implement control methods have been unsuccessful.

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Inland Water Fungi in the Anthropocene: Electric current and Future Perspectives

, …
, in

Reference Module in Earth Systems and Environmental Sciences, 2021

Aquatic fungi

A recent approximate based on molecular evidence suggests a global fungal diversity of about 1.v 1000000 species (Hawksworth and Lücking, 2017
Aquatic fungi
form a taxonomically and morphologically diverse group in freshwater, brackish, and marine habitats. In parallel to their diverse lifestyles, customs composition and abundance of fungi vary considerably with their aquatic habitats (

Wurzbacher et al., 2010). Interestingly, well-nigh 96% of all fungal taxa accept been recorded in temperate regions and fewer in tropical and subtropical regions (Rossman, 1994;
Hawksworth, 2001;
Duarte et al., 2016;
Hyde et al., 2016). Therefore, the “true” number of fungi should exist much higher, i.e., ii.2–3.8 million species, because a substantial fraction of the global fungal multifariousness has not been explored in-depth (Grossart et al., 2019).

The number of isolated and described fungal taxa is much lower than global estimates, including only 120,000–143,273 species (Fungorum, 2018;
Wijayawardene et al., 2017). The bulk of fungal species are related to the two phyla Ascomycota and Basidiomycota (ca. 96,000 species), which form the subkingdom Dikarya. Our electric current knowledge of fungal diversity is quite limited (Tedersoo et al., 2014), particularly in aquatic systems where the number of described species is depression (ca. 3000–4000 species) equally compared to terrestrial fungi (Jones et al., 2014). Consequently, the number of newly discovered fungal species in aquatic systems is predicted to increase (Voigt and Kirk, 2011).

Gessner and Van Ryckegem (2003)
suggested that at that place are ca. twenty,000 different species of freshwater fungi, notwithstanding only ~
5% of the estimated fungal species have been described. The estimated number of species documented from dissimilar habitats and substrates include 622 fungal species of ascomycetes, 600 hyphomycetous fungal species from
litter (Gessner and Van Ryckegem, 2003), 531 asexual fungal species, 317 species on peat swamp (Tsui et al., 2001;
Sivichai et al. 2002), and 183 trichomycetes. Also, zoosporic fungi comprise more than 500 species of chytrids and members of fungal-like organisms (Jones et al., 2014). All other fungal groups, however, are poorly described, including freshwater lichens with nigh 270 lichenicolous fungi and lichens, 226 fungal species on aquatic plants described as dark septate endophytes or endomycorrhizae, and 40 species of parasitic fungi. In item, basidiomycetes are poorly documented in freshwater ecosystems, with but 41 non-yeast basidiomycetes and 74 basidiomycetous yeasts. The overall documented species richness of freshwater fungi (<
4200 species) suggests that there are still many freshwater habitats and substrates to be surveyed (Jones et al., 2014).

In aquatic systems, iii major types of fungi tin be found depending on their growth and accommodation abilities in aquatic ecosystems: (I) terrestrial fungi that are often passively introduced into the water via high loads of fungal propagules from inflowing streams, rainwater runoff, and current of air. This fungal grouping is known as

transient fungi

(versatile immigrants), which exhibit no activity in h2o – presumably due to unfavorable aquatic conditions or interactions with organisms (Dix and Webster, 1995;
Voronin, 2014). (Two) Partially adapted aquatic fungi that may be amphibious with one stage of their life cycle underwater and some other phase dispersed in air-water boundaries (
aero-aquatic hyphomycetes

Dix and Webster, 1995;
Park, 1972
or periodic immigrants). (III) Fully adapted aquatic fungi (indwellers including Ingoldian fungi;
Ingold, 1942) that tin maintain their biomass in aquatic ecosystems with constant activeness from twelvemonth to yr. They utilise substrates and nutrients available in water bodies, and most are capable of sporulating directly in water (Grossart et al., 2019).

Based on their morphology and lifestyle including different functional behaviors (independent of phylogeny), aquatic fungi are further separated into six major groups (Wurzbacher et al., 2010):


Aquatic hyphomycetes
are recorded on decaying leaves and lignocellulosic droppings in freshwater ecosystems worldwide. Aquatic


(Nilsson, 1964), also known every bit amphibious


(Michaelides and Kendrick, 1978), comprise


fungal taxa of ascomycetes and basidiomycetes (Shearer et al., 2007) that are specifically adapted to aquatic habitats via their reproductive systems past producing their spores in relatively large multiradiate (often tetraradiate), sigmoid or spherical conidia with tips commonly covered with mucilaginous mucilage (Read et al., 1992) to facilitate attachment to and colonization of a specific substrate. Aquatic


are categorized into two ecological groups according to their reproductive behavior (Goh and Hyde, 1996): (a) the

Ingoldian fungi

(Ingold, 1942) are characterized by their ability for sporulation on plant materials underwater and (b) the

aero-aquatic fungi

that do not sporulate underwater but need air exposure for sporulation to complete their life cycle (Wurzbacher et al., 2010). On the other hand,
Goh (2003)
provides some other common grouping of aquatic hyphomycetes, i.e., transparent fungi with asexual reproduction (mitosporic) and dark conidia (coelomycetes) that have been recorded from various freshwater habitats. Still, their conidial structure is not too adapted for the aquatic ecosystems as the



aero-aquatic hyphomycetes

(Goh and Hyde, 1996). These fungi include 2 ecological groups, namely, indwellers that are present only in freshwater environments (due east.g.,
Camposporidium) and immigrants that occur in both terrestrial and freshwater environments ( thousand.,
Arthrobotrys) (Park, 1972).


True zoosporic fungi
currently include phyla Chytridiomycota, Neocallimastigomycota, Kickxellomycotina, and Blastocladiomycota. They commonly occur as saprobes in the degradation of particulate organic matter of expressionless animals, pollen grains and plant litter likewise as parasites of vertebrate animals, eastward.g., frogs, zooplankton and phytoplankton, or as symbionts in the mammalian digestive system. Consequently, zoosporic fungi take significant ecological roles in nutrient cycling and regulation of the populations of phytoplankton in aquatic ecosystems and likewise cause some economically important plant and animal diseases (Gleason et al., 2017). True zoosporic fungi typically occur in the pelagic zone of standing waters (Wurzbacher et al., 2010, 2016) and their reproductive units display main adaptations to an aquatic lifestyle in the form of uniflagellated motile zoospores (Wong et al., 1998).


Aquatic ascomycetes and basidiomycetes

phase; develops sexual reproductive units including ascospores characteristic for ascomycetes and basidiospores for basidiomycetes) are microscopic fungi that decompose submerged woody cloth that falls into aquatic habitats. Since the 1990s, several studies apropos freshwater ascomycetes accept been performed increasing the number of described species from 370 (Shearer, 1993) to 622 species (Cai et al., 2014;
Shearer et al., 2014). Currently, virtually 675 species related to freshwater ascomycetes have been characterized and comprise several taxonomic groups (i.eastward., dothideomycetes, sordariomycetes, and leotiomycetes) ubiquitously found in freshwater on submerged and exposed woody droppings (Jones and Pang, 2012;
Shearer et al., 2014). The bulk of freshwater ascomycetes class microscopic ascomata (less than 0.five
mm) and incorporate structurally h2o-adapted ascospores characterized by several sheaths or wall ornamentations covered by a gel-like gluey material that supports spore dispersal and attachment (Digby and Goos, 1987).


are unicellular fungi with spherical or oval-shaped cells, representing a diverse grouping belonging to ascomycetes and basidiomycetes (Shearer et al., 2007) that are institute mainly in the pelagic zone of freshwater habitats (Wurzbacher et al., 2010) and the pelagic and estuarine habitats of marine systems. Our understanding of their ecology and functions in aquatic ecosystems is still limited (Wurzbacher et al., 2010). However, they may play a similar role as heterotrophic bacteria generally referred to equally the main (micro)organisms taking upward and re-mineralizing dissolved organic matter.


represent another nether-studied grouping of aquatic fungi with little information on their ecology, composition and role in aquatic ecosystems (Goh and Hyde, 1996). The bulk of glomeromycetes is terrestrial, except for aquatic trichomycetes (Shearer et al., 2007), and course a polyphyletic group which grows parasitically or mutualistically (order Harpellales) together with aquatic arthropods (Hibbett et al., 2007;
Jobard et al., 2010). In addition, Glomeromycota are comprised of ecologically beneficial mycorrhizal fungi forming symbionts with the roots of aquatic macrophytes. These mycorrhizal fungi are characterized by the germination of special structures (vascular and/or arbuscular structures) inside the establish roots providing the found with nutrients, eastward.g., phosphorus in food-limited aquatic ecosystems (Wurzbacher et al., 2011).


Fungi-similar organisms
(Oomycetes, Straminipila) are well-documented (Wong et al., 1998) and considered the nigh ubiquitous aquatic “fungal” group characterized by biflagellate heterokont (2 unequal flagella) zoospores (Dick, 1989;
Shearer et al., 2007). Although Straminipila (hyphochytriomycota, Oomycota, and labyrinthulomycota) share like morphological and physiological traits with true fungi (chytridiomycota, rosellomycota, and aphelida), their ecological functions and trophic strategies appoint them as false fungi (Alexopoulos et al. 1996;
Beakes et al. 2014;
Karpov et al. 2014).

Although cultivation is oftentimes biased, e.g., by sample handling and the choice of media, more than fungal isolates from aquatic ecosystems are required to meliorate characterize their genetics, physiology, and ecological role (Grossart et al., 2019). Yet, it remains difficult to characterize and estimate total fungal diversity at any given sampling site, oft due to the lack of experience and qualified staff and suitable identification manuals, particularly in tropical regions. There is a great need to provide new techniques and strategies to isolate and assess fungal diversity and enable realistic site estimates for conservation purposes (Cannon, 1997
Hawksworth, 2001). The application of unlike isolation techniques to the same waterbody may yield entirely different fungal communities (Abdel-Raheem, 2004;
Sridhar et al., 2010). Whereas straight observation techniques tin exist used for investigations of growth of

zoosporic fungi
, aquatic




fungi on different substrates (Müller-Haeckel and Marvanová, 1979;
Sparrow, 1968), the baiting technique is commonly used for isolation of

zoosporic fungi

and aquatic


from water samples using specific baits such as boiled sesame and hemp seeds (for oomycetes, fungal-like organisms), phytoplankton, pollen grains, and snakeskin (for chytrids) and plant leaves (for aquatic

) (Shearer and Von Bodman, 1983;
Shearer, 1972;
Sparrow, 1968). Furthermore, the moist chamber technique can exist employed to isolate


fungi using woody blocks (Shearer and Von Bodman, 1983;
Shearer, 1972). Finally, yeasts can be obtained past dilution plating of water or sediment on specific media (Fell, 2001;
Kumar et al., 2011). Although most aquatic fungi remain uncultivated, new methods, baits, and media may isolate the unabridged fungal customs in aquatic systems.

The phylogenetic relationship of aquatic fungi, including Ascomycota, Basidiomycota, Chytridiomycota, Neocallimastigomycota, Kickxellomycotina, Blastocladiomycota, and fungi-like organisms is given in
Fig. 1. Recently, a new and surprisingly big fungal variety has been discovered in aquatic habitats using molecular tools. These so-called

dark matter fungi

are mainly related to the early on branches of the fungal tree, i.e., Aphelida, Rozellomycota, and Chytridiomycota (Grossart et al., 2016). Thus, considerable efforts to discover and evaluate their environmental and ecophylogenetics are needed. For example, their role as parasites or saprotrophs nevertheless needs to be identified and quantified ( thousand.,
Banos et al., 2020). Whereas parasites exploit their living host for nutrition, saprotrophs use an array of excreted (extracellular) enzymes to digest their dead nutritional substrate directly (e.g., dead organism or other nonliving organic matter).

Current conceptual models indicate a multitude of different processes by which aquatic fungi transform and comprise



autochthonous organic matter

into organismic biomass and transfer information technology to higher trophic levels. Recently, 3 major processes have been identified to describe the dissimilar ecological roles of fungi in the aquatic realm (Grossart et al., 2019): (i)

, (2)

, and (3)

benthic shunt



has been well described (Kagami et al., 2007, 2014) and refers to parasitic fungi that render inedible phytoplankton available to zooplankton grazers by producing zoospores or by fragmentation of big phytoplankton cells. The


relates to the important function of fungal interactions in organic matter and organisms that result in aggregation or disintegration of sinking organic particles, including living organisms and dead cell debris (Grossart et al., 2019). Near consequences of the mycoflux are still unknown, but we propose that they significantly affect the efficiency of the aquatic carbon pump and hence carbon sequestration. The

benthic shunt

describes how fungal colonization of (mainly terrestrial) organic litter and the formation of fungal biomass allows for an efficient transfer of this organic matter to macrozoobenthos on the sediment (Attermeyer et al., 2013). Macrozoobenthos represents an fantabulous food source for higher trophic levels in the pelagic zone, such as fish, and thus increases the efficiency of trophic transfer throughout the aquatic benthic and pelagic nutrient webs. These three concepts take the various lifestyles and interactions ( thousand., parasitism and saprotrophy) of aquatic fungi into account and highlight their ecological and biogeochemical importance in freshwaters. In sections “Aquatic fungi-like organisms” and “Fungi-virus interactions: An emerging topic” we depict two prime examples for interactions with fungi-like and fungi interactions with organisms and virus which until now have received only a footling attention.

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URL: discipline/article/pii/B9780128191668000256

The Groundwater Mycobiome: Fungal Diverseness in Terrestrial Aquifers*

, in

Reference Module in World Systems and Environmental Sciences, 2021

Where practise groundwater fungi originate from?

The question of what the source of fungi recovered from groundwater forms is not then easy to reply. Yet,
aquatic fungi
in general and groundwater fungi, in particular, tin be divided into ii broader groups. These are “resident fungi” and “transient fungi.” Resident fungi are those specimens that tin complete their life bicycle in the aquatic realm and are not encountered in terrestrial habitats. In contrast, transient fungi are those that enter the aquatic environment from terrestrial sources and tin can adapt well to local conditions or remain inactive in the form of spores (

Shearer et al., 2007). For example, a robust adaptive chapters is exhibited by groundwater fungi found in karst aquifers, which make upwards the majority of the fungal OTUs found in these landscapes. These are presumably transported from the surface into the groundwater system, facilitated by fractures, underground drainage systems, as well as the large voids of karst during recharge events (Nawaz et al., 2016). The presence of terrestrial fungi in aquatic systems (transient fungi) raises a relevant question about the ability of unlike fungal taxa to adapt to the aquatic surround.

A recently published report on subterranean aquifers has shown the presence of diverse fungal OTUs of the terrestrial origin or known to exist parasitic fungi of diverse crops in the agile fraction of groundwater fungal communities recovered (Nawaz et al., 2018). This raises the question of whether and how the fungi take undergone specification in groundwater and whether obligate groundwater species be at all. With the current land of information bachelor on groundwater fungi, these questions are difficult to respond unless there are hypothesis-driven studies on these topics either in natural settings or in well-designated lab experiments.

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