Fungal connections (3.3)

articles

The previous two pages in this series regarding 'fungal connections' dealt with specific subjects, starting with fungal mycelium and mycorrhizal fungi, and then saprotrophic fungi, whereas this final page is more of a mixed bag as it covers various topics from fungal guttation and pin moulds, to lichens and rust fungi.

3.1: Fungal mycelium

3.1a: Mycorrhizal fungi - specifically the ectomycorrhizal 'mushrooms' and their symbiotic relationship with trees

> Mycorrhizal fungi - diversity in a genus (Amanita)

3.2: Saprotrophic fungi

> Brackets and Polypores > Cauliflower fungus > Corticoid (crust) fungi > Pleurotoid agarics

> Saprotrophic agarics > Bonnets > Clavaroid (coral) fungi > Jelly fungi > Cup fungi > Flask fungi

3.3: Fungal guttation

3.3a: Mucorales - pin mould

3.3b: Dendrostibella smaragdina

3.3c: Cystofilobasidium macerans - Sap Yeast

3.3d: Lichenised fungi

3.3e: Pucciniomycetes - rust fungi

Associated information:

Appendix 3A: Ectomycorrhizal fungi partnerships

Fungal guttation

3.3 (v.1)

The presence of tiny water droplets clinging to the body hairs of a springtail or transforming a spider's web into a sea of pearls (first photo) would typically add an extra element of interest to almost any macro subject but, apart from the first image, all the 'drops' seen here have been created by the secretion of excess fungal fluids, not from atmospheric moisture causing dew drops.

Informally, these drops of fluid are often described as 'mushroom sweat' but the correct term is fungal guttation. The liquid is a build up of excess absorbed water coupled with various enzymes and compounds that the fungus needs to clear during periods of rapid growth and/or due to external conditions. For most of the time fungi invisibly seep this waste matter through their pores, but too much absorption increases pressure such that it's squeezed out.

These droplets are most likely to be seen on the fertile surface of wood-decay polypores and crust fungus, rather than on agarics or boletes, but also on some other species including a few where the guttation is actually a distinguishing feature of the fungus. And, as well as being found on the fruiting bodies, these droplets can also form on mycelium as the final two photos, or on aerial pin mould hyphae. The exudes are usually clear, milky or yellowish in colour, but darker, orange, red or brown drops are not uncommon, especially during drier periods when the liquid is less diluted than it is in wet conditions.

As a point of interest, all of the droplets in the following photos were found on fungi or mycelium that was hidden away on the underside of deadwood, that was mostly relatively large logs that I'd temporarily rolled over to check what I could find.

Dew drops in a spider's web for comparison

A single large, dark coloured blob of guttation on a polypore

The different colours and reflections that you can capture when photographing guttation can produce stunning images

I don't know the identity of this fungus, but the amber-coloured blobs of guttation certainly add an extra something to the photos

A couple of rather nice examples showing numerous tiny drops of exuded liquid spreading across mycelium

Mucorales - pin mould

[article requires more information and photos]

3.3a (v.1)

From a personal point of view I find it hard to comprehend that up to a few months ago (September 2025) I hadn't really given the world of fungi much interest at all apart from taking the odd photo of a 'pretty mushroom', whereas I now want to learn as much as I can about each of the different morphological groups. I never realised when I started this series of articles on woodland ecology that I would become so absorbed by these fascinating organisms or that I would end up with so many different subject matters, but of course that was the whole point of the exercise - discover and learn.

In that respect it doesn't surprise me that I've been particularly drawn to the smaller, mainly saprotrophic forms, rather than the larger more familiar species. In fact, the more unusual or weird the better as far as I'm concerned and, I suspect, that I'm probably not going to find many that are as fascinating as the pin moulds featured here. There aren't that many species that I'm going to be able to find in my local woodlands, but it's definitely a group that I want to explore.

I appreciate that I've made this point before, but for anyone that has stumbled across this page, please note that this article is purely my attempt at trying to obtain a basic understanding of pin moulds and to have some knowledge regarding the species that I might encounter. Information has been gathered from various sources, checked as carefully as I can, and written up in my own words. Whilst there's a fair amount of information available regarding zygomycetes in general it's usually associated with agricultural or household moulds, such as the well-documented black bread mould Rhizopus stolonifer, biotechnological uses and laboratory applications, rather than the species I'm hoping to find, so it's taken a fair amount of digging to come up with some of details and descriptions given here.

Without doubt, I need more knowledge and I certainly need more photos, so I'm hoping that over time the article will evolve to ensure completeness and accuracy of details.

The higher-level classification arrangement of the zygomycetes has recently been redefined through phylogenetic analysis, Spatafora et al. (2016), which has left some taxa in uncertain (incertae sedis) position. The upshot of this analysis is that the zygomycetes now comprise two major clades, Mucoromycota and Zoopagomycota, currently defined as phyla, thereby abandoning the traditional Zygomycota. Under this arrangement the Mucoromycota now includes three subphyla - the arbuscular mycorrhizae-forming Glomeromycotina (see article 3.1a); Mortierellomycotina, which are mainly root endophytes; and the Mucoromycotina incorporating two primary orders, Endogonales and Mucorales.

Although this group includes a few weak parasites, most Mucorales are saprobes that grow on organic matter such as soil, dung or fruit. They are broadly characterised by having abundant, rapidly growing mycelium typically with long hyphae that develops in the substrate and, through asexual reproduction when conditions are right, produce erect sporangiophores that support sac-like sporangia. Of course they also reproduce sexually through the formation of zygospores, but that's way outside the scope of this simple article that focuses on general appearance and visible macroscopic features.

Mucorales comprises eleven families with numerous genera and species but, as far as I can see, there are only three families and probably no more than five or six genera that are likely to be discovered and photographed in the forest or open pasture woodland. Whilst some pin moulds can be identified reasonably easily, the tiny size, variable nature and limited visible characters make it almost impossible to distinguish individual species from certain genera. The following is my best effort of trying to describe and identify species I've seen or hope to see.

Mucoraceae - the largest family with 20+ genera, including Mucor and the monotypic genus Syzgites.

Mucor mucedo is the 'type species' of the genus, and is found across many areas of the world in all sorts of environments; contaminating grain and fruits, damaging cheese or even infecting animals. In nature though, the species is most commonly found in soil growing on dead or decaying organic matter, or more frequently on dung where it is usually the first saprotrophic coloniser. Growth is rapid, initially with a fluffy appearance, but with sporangiophores soon starting to appear. Subject to conditions the sporangiophores can grow to between 2-3cm tall. They are unbranched and pale greyish in colour. The sporangia, being the terminally-formed closed sacs, are either concolourous or pale beige, turning black at majority. They measure in the region of 150-200µm across.

Mucor mucedo will grow and produce sporangiophores at temperatures as low as 5°C (as below), which isn't necessarily the case with other less common members of the genus. The temperature has a significant effect on growth and appearance. Up to 15°C, it will produce shorter, often recurved, sporangiophores than it would when the temperature is more in the region of 15-25°C.

Despite being known as the 'common pin mould' it is very rarely recorded. Other species may come up during general internet enquiries about the genus, notably Mucor hiemalis, which grows on unspoiled foods; Mucor racemosus which colonises various habitats that could possibly include dung, but has a very different appearance; and Mucor piriformis which causes soft rot in fruits, grows in clusters and has a totally different look, and according to the NBN Atlas was last recorded over 30 years ago. So, given that information and everything I've read, I'm as confident as I can be that the specimens featured here are indeed Mucor mucedo.

Syzygites megalopcarpus is a necrotrophic mycoparasite that colonises many different species of moribund fleshy mushrooms, such as Amanita, Boletus and Russula. The impressive, fast-growing mycelium can initially appear yellowish due to the presence of carotenoid pigments, otherwise greyish-white, later turning bluish-grey to golden-brown I believe, although I haven't personally seen any of those darker examples. The sporangiophores are multi, dichotomously branched, and the tiny sporangia, that only measure 50-150µm (unfortunately not present or visible in any of the following photos), range from yellow to grey coloured as they mature. Syzygites megalocarpus is the sole member of its genus.

Phycomycetaceae - includes just two genera Phycomyces and Spinellus

Phycomyes - three species are listed, although only Phycomyes blakesleeanus and Phycomyes nitens are normally considered; the latter being the originally described form, and the former now regarded as the 'type species' of the genus. They can only be reliably separated by close examination of the spores with those of Phycomyes nitens being somewhat larger, but for general identification purposes they could effectively be treated as the same species.

In natural habitats, Phycomyes is most likely to be found colonising moist organic substrates especially herbivore dung from small rodents such as mice through to larger species like deer or horses. They may also be found on other forms of organic matter in the soil; typically in neutral to slightly acid habitats.

When conditions are right, usually when the temperature is above 10°C, the sporangiophores will sprout up from the mycelium at a pretty rapid rate of up to 2mm/hr. The tip swells to form a bright yellow sporangium before a lull of several hours during which time the stalk does not lengthen. Growth will then resume with the sporangium quickly turning dark brown or black. Of course this is happening at different rates such, that if the timing is right, you should be able to see some newly formed yellow sporangium mixed in with the mature black ones. The sporangiophores are unbranched and once they start to extend will twist in a counterclockwise direction and then reverse. They may grow as long as 10cm or more, although the lack of support will usually limit their spread. The sporangia are only around 100µm in diameter. The species is also known for being light sensitive, responding to and growing to light.

Although the mycelium of these species is regularly detected in dung during surveys, fruiting growth is rarely observed in the wild as it appears and declines so quickly, so on the assumption that the specimen featured below left, growing on what I assume to be a small dung pellet, is indeed Phycomyces as suspected, it was a rather lucky find. The species on the right is questionable, but was found a couple of weeks later in close proximity to where the first shot was taken

Spinellus fusiger - commonly known as 'bonnet mould', this mycoparasite or 'facultative parasite', is most often found growing on the caps of various Mycena spp. or very occasionally on other small agarics such as Hygrophorus and Collybia.

It's a particularly photogenic mould that I really want to find, but at the moment I can only confirm that it's characterised by dense clusters of erect, radiating sporangiophores that emerge from all over the cap forming a pale brownish-yellow pin-cushion structure that gives the fungus a spiny appearance, hence the generic name Spinellus. The sporangiophores can grow as long as 3cm, each terminating in a dark, spherical sporangia that is 120-300µm in diameter. The texture is fragile and cottony, easily disturbed by touch, wind or rain and, therefore, there's an element of luck involved in finding them at their best. There are a couple of other species in the genus, but as far as I'm aware they do not occur in Britain.

[photos required]

Pilobolaceae - includes just two genera Pilobolus and Utharomyces

Pilobolus - commonly known as the 'dung cannon', is a tiny, coprophilous fungi that has a unique ballistic spore discharge mechanism that ejects the sporangium with incredible force. The spores develop in the sporangia in normal fashion, but to propel the sporangia the stalk swells up with mucus forming a ballon-like vesicle just below the black lens-shaped cap. Once released, the pressure enables the sporangia to be propelled away from the dung where the sporangiophores are growing. They can end up a metre or more away, but it's not done randomly as the sporangiophore is able to control both the angle and direction of fire. I'm not totally sure why, but apparently, they're always projected towards the sun where it is hoped that they will come to rest safely in the grass where they won't get trodden on. It's then a case of waiting, as the life cycle of these species is dependent on the herbivore grazing habits as the spores need to be ingested whilst the cow or horse is eating the grass, but then must pass intact through the animal's gut in order to germinate within fresh dung.

Five species have been recorded in Britain all of which have slightly differently shaped sporangia, but I don't believe that they're distinctive enough to confirm the species except possibly in the case of Pilobus umbonatus which, as its name suggests, has an umbo. I've also got comparative photos of that species alongside Pilobus crystallinus and they look very different so I'll need to do some more research once I've managed to find and photograph them.

[photos required]

Undetermined

Inevitably there are going to be species that I photograph which I haven't yet been able to identify or, indeed, may never be able to identify, such as these two.

The first one is proving particularly frustrating as there are some distinctive features, which I hope will lead to confirmation of

a genus at some point. Whether or not the surrounding mycelia is connected, which I actually doubt, the the mould at the bottom of the mushroom stem appears to be two separate clumps with radiating growth, which is particularly evident in the tiny patch at the top of the stem, and what looks like, long, unbranched, ribbon-like hyphae that are tapered towards the tip. The thick strand of hyphae draped over the top of the deformed stem of the mushroom (likely Lactarius sudulcis, which was found tight to the side of a rotting Beech log) could also provide clues if it's connected to the mould. More importantly, close examination of the hyphae mass on the right clearly shows a dozen or more dark coloured sporangia.

It's been suggested that it's probably just a mass of fungal mycelium, but I'm pretty sure it's not as the structure is just wrong to my eyes. I would really like to know, so I'm going to continue the research, which interestingly has led me to one of the related orders Mortierellales, and possibly the species Mortierella armillariicola as it has a not dissimilar appearance from photos that I've seen on iNaturalist. I obviously need to do more research, but for now I'll leave those thoughts hanging ...

The other photo has been cropped in quite a lot, but the slime mould (likely Stemonitopsis sp.) is clearly in early stages of being attacked by what appears to be a mass of multi-branched hyphae, some appearing quite thick and ribbon-like. At present, I'm assuming it belongs somewhere in this group, but I could be wrong!

Dendrostilbella smaragdina

3.3b (v.1)

ASCOMYCOTA > Leotiomycetes > Helotiales > Tympanidaceae

This very rarely recorded, tiny, rather striking asexual (anamorph) synnematoid fungi has scattered black clubs (synnemata) typically just 800-1200µm tall with a bright blue-green gelatinous head filled with conidia that darkens with age, supported on cylindrical or slightly tapering black stems. Commonly known as the 'teal conifer pin' as it usually occurs on conifer bark, although most of the few confirmed British records for the species, of which there are only seven on the BMS database at the time of writing, are on deciduous wood. The examples featured here were found on the underside of a largish piece of very wet, well-rotted deadwood, which couldn't be determined, but was possibly Hazel.

Cystofilobasidium macerans - Sap Yeast

3.3c (v.1)

Cystofilobasidium macerans [Tremellomycetes > Cystofilobasidiales > Cystofilobasidiaceae] is the sexual (teleomorph) yeast state of Cryptococcus macerans [Tremellales > Cryptococcaceae], which combines with bacteria and certain types

of fungi to form the slimy, orange, often bubbly substance that is occasionally seen oozing out of tree wounds.

The appearance of this slime, commonly known as Deer Vomit or 'orange-goo' which has no connection with slime mould

per se [Myxomycetes], is typically associated with cooler, wetter conditions during late winter or early spring when sap and nutrients that have been stored in tree roots are transported to the branches to enrich new growth. The sap comes up from the roots under pressure and if the tree has any cuts or wounds that are open to the elements there is likely to be seepage. Similarly if a tree has been felled, as the roots may still be alive and will continue to pump the sap in to what's left of the tree, which is why it is often seen on stumps or on the ends of cut logs.

Sap, or more specifically exuded sap that has been infected with bacteria, attracts wild yeast which interacts with the primary coloniser, which is usually the Ascomycete fungus Fusicolla merismoides, formerly genus Fusarium, [Sordariomycetes > Hypocreales > Nectriaceae]. In this context the fungus provides the sap with body, whilst the yeast ferments within the sap producing carbon dioxide which creates the characteristic orange bubbles. Some literature attributes the colour to either the fungus or the yeast, but in practice it's a result of the interaction between the two organisms which produces carotene - the same orange pigment found in carrots.

Although Deer Vomit is specifically linked with Fusicolla merismoides, every example that has been properly examined has produced a different DNA sequence suggesting that each specimen is a unique complex of different organisms.

Whilst Cystofilobasidium macerans appears to be a constant element, other fungal pathogen species including Fusarium acuminatum, Epicoccum nigrum and Aureobasidium sp., have been detected. In some cases the fungus and associated microbes are existing in some form of symbiotic relationship, whereas others have been identified as parasitising each other.

The biological process here is way beyond my understanding as a photographer of these species, but it is interesting to learn a little bit about some of these unusual fungal forms.

Confusion arises when common names are replicated or incorrectly applied, and there are a couple of these that regularly come up in articles about this species. The first is that Deer Vomit is also used in the US, and possibly elsewhere, as another variant of Dog Vomit (an accepted alternative of Scrambled Egg Slime) in respect of the slime mould Fuligo septica.

The other is Slime Flux, which is an entirely different form of bacterial disease more formerly known as Bacterial Wetwood

that affects certain trees such as Ash, Elm and Oak. Whereas the 'orange-goo' in the featured form above is usually brightly coloured with a feint sweet or yeasty smell, Slime Flux is expressed as a dark-coloured, often foul-smelling, foamy and watery slime that streaks down the bark. Rather than starting from bacteria within the sap, it emanates from the tree's heartwood or sapwood, with the resultant infected liquid and gasses being forced out of cracks in the trunk. Once exposed to the air it will quickly become further infected by various yeasts and other fungi, at which point it is known as Slime Flux.

At this stage it will also become attractive to various insects, such as flies and ants. Deer Vomit may look unsightly, but it's harmless and doesn't last for long, but Slime Flux is a long-term and potentially damaging condition [photo needed].

Lichenised fungi

3.3d (v.1)

The vegetative body of lichenised fungi (lichens), called the thallus, is composed of two, or sometimes more, dissimilar organisms that form a mutually beneficial (symbiotic) partnership. The primary element is fungus which typically makes up 80% or so of the body, with the partner most often green alga and/or cyanobacterium. The fungus provides support and can absorb moisture from the air, but as they do not have roots like plants depend on the alga and cyanobacteria which possess the green pigment chlorophyll to produce carbohydrates through photosynthesis.

The fungal component is called the mycobiont. Virtually all lichens have an ascomycetous mycobiont, but there are a few basidiomycetes that are lichenised, notably some agarics of the genus Lichenomphalia (as featured below) and a few small clavarioids in the genus Multiclavula. They are classified utilising the scientific name of the fungus.

The photosynthetic partner or photobiont of most lichens is normally green algae (Chlorophyta) from the genera Trebouxia [class: Trebouxiophyceae] or Trentepohlia [class: Ulvophyseae] and a few others including Chlorella, Diplosphaera, and Myrmecia. However, there are some species, known as 'cyanolichens' where cyanobacterium is the main photosynthetic component, and others that combine with both green algae and cyanobacterium. The most frequent cyanobacteria partners are from the genus Nostoc [class: Cyanophyceae]. The colour of the lichen is largely determined by the photobiont rather than the fungal element even though it's the primary component.

Whilst the fungus cannot survive without the carbohydrates produced by the photobiont, and in many cases the algae cannot grow or reproduce on its own, there are exceptions as some algal symbionts are able to live independently. The best and most visible example in woodland habitats particularly is the alga Trentepohlia, which forms orange-coloured populations on tree trunks (as featured below).

Some species of fungi live on the thallus as an obligate parasite rather than as a component part of the lichen. They are known as lichenicolous fungi and should not be confused with lichenised fungi. One of the relatively common and more visible species is featured below.

Lichens are featured separately in their own section, which provides some basic information regarding growth forms and reproduction, as well as 150+ individual species accounts. The woodland collection includes most of the species I'm likely to find locally, but in terms of this series of articles there also a number of lignicolous and corticolous Cladonia species that will regularly be seen on deadwood and growing on trees. A few common [Lecanoromycetes >] examples are shown below.

Graphis scripta s.lat

Ostropales > Graphidaceae

Physcia tenella

Calicales > Physciaceae

Flavoparmelia caperata

Lecanorales > Parmeliaceae

Xanthoria parietina

Teloschistales > Teloschistaceae

Evernia prunastri

Lecanorales > Parmeliaceae

Ramalina farinaceae

Lecanorales > Ramalinaceae

Lichenomphalia umbellifera (syn. Omphalina ericetorum)

BASIDIOMYCOTA > Agaricomycetes > Agaricales > Hygrophoraceae

The members of this genus live in mutualistic symbiosis with green algae, forming a grainy or leaf-shaped thallus from which the fruitbody arises. Lichenomphalia umbellifera is a deeply decurrent gilled omphalinoid fungus with a tan-coloured umbilicate cap that can become very deep and funnel-shaped. The margin unfurls with age and often becomes pleated or scalloped, making the cap look slightly veined. Typically occurs on moss-covered fallen trunks or logs in damp woodland, and could be easily overlooked as just another small brown mushroom.

Lichenomphalia umbellifera

Trentepohlia spp.

CHLOROPHYTA > Ulvophyceae > Trentepohliales > Trentepohliaceae

Trentepohlia is a genus of filamentous green algae, which is symbiotically associated with lichens as previously noted, but also exists as a free-living organism on the damp, shaded side of tree trunks and other substrates. The 'type species' of the genus and the most widespread form in Britain is Trentepohlia aurea. It consists of macroscopic small bushy tufts which range in colour from golden yellow to orange-brown; the colour resulting from the carotenoid pigments in the algal cells.

In combination with fungal hyphae, they form another defined type of lichen known as a 'protolichen' where they are the phycobiont partner. This form is particularly associated with the crustose 'script lichens' of the genera Arthonia, Graphis, Graphina and Opegrapha.

There are numerous other free-living algal photobionts, but the majority are microscopic species which have been recorded from soil.

Green Algae - Trentepohlia aurea

Erythricium aurantiacum (syn. Marchandiobasidium aurantiacum)

BASIDIOMYCOTA > Agaricomycetes > Corticiales > Corticiaceae

Asexual (anamorph) parasitic lichenicolous fungus that forms tiny grainy, pastel orange bulbils up to just 150µm diameter, occasionally forming basidia, but not conidia. Can occur on various lichens, but especially on Physcia and often spreading to the thallus of any adjacent species.

Erythricium aurantiacum (example of a lichenicolous fungus)

Pucciniomycetes - rust fungi

3.3e (v.1)

I was in two minds whether to include an article on rust fungi as I've only photographed a couple of species, which were actually found in grassland rather than woodland habitat, but on the other hand Pucciniomycetes is one of the primary divisions (classes) of Basidiomycota so it should be mentioned if only briefly. It's a very large and diverse group that contains around twenty families of rust fungi in five orders.

The Puccinials is by far the largest order representing, on a worldwide basis, around 7,000 species, the majority of which are in the Puccinia genus. I have no idea how many occur in Britain and apart from taking the odd photo if a particular species has caught my attention, I don't see myself taking more than a cursory interest.

They are obligate plant pathogens that cause damage to various degrees, some severely, but rarely to the point of killing the host. Each species has a range of hosts and, in fact, can infect two different species, during their life cycle, but they cannot be transmitted to non-host species. Beyond that it gets very complicated, so I'll simply close this article off with a couple of examples including Puccinia cnici-oleracei, which has to be one of the most attractive species you could hope to see if found at this stage of development.

Puccinia cnici-oleracei [Pucciniaceae]

on Melancholy Thistle [Cirsium heterophyllum]

Triphragmium ulmariae [Sphaerophragmiaceae]

on Meadowsweet [Filipendula ulmaria]

Puccinia cnici-oleracei [Pucciniaceae]

on Melancholy Thistle [Cirsium heterophyllum]

Triphragmium ulmariae [Sphaerophragmiaceae]

on Meadowsweet [Filipendula ulmaria]

Melamspora rostrupii [Melampsoraceae]

on Dog's Mercury [Mercurialis perennis]