Amoebas Prey Upon Algae in Aquatic Environments

Introduction

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 (east.one 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.

What are aquatic fungi?—Functional and taxonomic nomenclature

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).

Aquatic Fungi

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

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

The genus
Coelomomyces
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
Coelomomyces
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
Coelomomyces
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
Coelomomyces
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.

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

456

),
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
Pythium

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

Non-Motile Aquatic Spores

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.

Coelomomyces and Lagenidium

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

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

The genus
Coelomomyces
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
Coelomomyces
has been cultured
in vitro.

Coelomomyces
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
Coelomomyces
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
Coelomomyces
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
Coelomomyces:
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
Coelomomyces
and
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.

A.

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;
Baldy
et al.
2002) and specific objectives of the study (e.thousand., upshot of pollution, inorganic nutrients, pesticides, etc. on these fungi) may dictate the choice of site.

Phylum Blastocladiomycota

The second type of sporangium, the meiosporangium, as well releases pond spores, simply these are formed by meiosis and give rise to haploid or
gametophyte
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
sirenin
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
Coelomomyces
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.

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
Phragmites
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).

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
and
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

hyphomycetes

,
and

teleomorphic

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

zoosporic fungi

and aquatic

hyphomycetes

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

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

teleomorphic

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 (east.one 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

allochthonous

and

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)

mycoloop
, (2)

mycoflux
, and (3)

benthic shunt
.

The

mycoloop

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

mycoflux

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 (e.one 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.

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.