Seasonal Update (October 2023)

Bottom of the rainbow. October can be a stormy month, with wind and rain never far away. - Credit: Marc Baldwin

Welcome to mid-autumn, or mid-spring if you're reading this in the southern hemisphere. The sixth of seven months with 31 days, October's name derives from ôctō, “eight” in Latin and Greek, a hangover from it being the eighth month in the calendar of Romulus. October was subsequently shunted to the tenth month when January and February were added sometime around 710 BC.

October is the middle of the pannage season here in the New Forest, where pigs are let out into the woodlands to eat acorn and beech mast - if you're interested in finding out more, check out my article on the common of mast.

Newly published

Due for release at the end of this month, the release date having been delayed, is a book I'd been eagerly awaiting since helping the authors with some sound clips and water deer information. Sound Identification of Terrestrial Mammals of Britain and Ireland from Pelagic Publishing, by Neil Middleton, Stuart Newson, and Huma Pearce, is an authoritative compendium of the vocalisations made by a comprehensive collection of 42 mammal species found throughout the UK and Republic of Ireland. The book describes the calls, provides context, and includes access to a library of more than 250 audio clips.

Weather review

Autumn started with a brief heatwave across much of Europe, including England and Wales. - Credit: WX Charts (CC BY-NC-ND 2.0)

September started on an unsettled and cool note before a ridge of high pressure built in for the first weekend, bringing consistently dry and warm conditions for much of the UK. Indeed, the summer that many had been hoping for over the past couple of months seemed crammed into the first week and a half of September, with temperatures widely into the high 20s Celsius (low 80s Fahrenheit) across England; some parts of the south-east saw 32.7C (91F) during the second weekend. This mini heatwave broke during the second week when a succession of low-pressure systems pushed in from the south and west. We saw some torrential rain and strong winds during the third week, and the month ended with some decent sunny spells mixed with rain and gale force winds courtesy of storm “Agnes”, the first named storm of the season. Once the storms passed, October was on track for starting on an unseasonably warm note, temperatures in the low to mid 20s Celsius.

Outside of the UK, Perth Airport in Australia exceeded 30C (86F) for the first time in its recorded history (79 years); its hottest winter day so far. The Cape Town Observatory in South Africa also reached a new high in its 63 years of climate data, and on the last day of winter in South America, temperatures peaked at 45C (113F) in Brazil, setting a new record. Early last month, Spain and Greece saw some torrential rain and flooding when the jet stream buckled, a lobe splintering off and becoming trapped below the main stream over Spain and Portugal - a meteorological feature known as omega blocking. Zagora in Greece recorded a staggering 528 mm (21 in.) of rain in only 10 hours, and locally some parts saw three years' worth of rain in only 48 hours. Hong Kong also saw some significant rain, 158 mm (6.2 in.) in an hour early last month, which was the highest on records that date back to 1884.

A naked mole-rat (Heterocephalus glaber). - Credit: Marc Baldwin

News and discoveries

Butter-for-brains? Many of us enjoy watching butterflies flitting between the plants in our garden, but most of us probably don't stop to think about the mental gymnastics going on between the wings. New data from the University of Bristol's School of Biological Sciences, published in Current Biology, suggests that these insects are smarter than we thought. The experiments show that longwings, brush-footed butterflies of the Heliconius genus, could remember decent foraging sites and establish long-term foraging routes that they used over several days.

Germinal genes. The global anti-aging market size reached US$ 67.2 billion in 2022 and is predicted to increase to US$ 98.6 billion by 2028, according to the IMARC Group. Now researchers have found evidence that it may be possible to, for want of a better analogy, transplant youth. According to a new study published in Nature, scientists have successfully transferred a gene that makes high molecular weight hyaluronic acid from a naked mole rat to mice. The mice showed improved health and their lifespan was extended by just over 4%.

Fishery fever. This year has seen unprecedented warmth in the surface waters of the Atlantic and Mediterranean Sea. Many scientists have raised concerns about the impact of marine heatwaves on aquatic life. Some recent research published in Nature suggests, however, that prolonged periods of unusually warm ocean temperatures don't appear to have had a lasting effect on the fish communities that are exploited to provide many countries with food.

Learned lapwings. Ground-nesting bird species are often at risk of predation and nest depredation from foxes and other predators, particularly in open farm landscapes where cover is sparse. A recent study, led by researchers at the University of Exeter, used 3D models to classify the nests of lapwings according to their shape and height, relative to their surroundings. The aim was to assess the degree of camouflage (so-called “occlusion”) and assess how likely they were to be found by predators. The results, published in Ecology and Evolution, show that the lapwings tended to select their nesting sites carefully based on the local landscape geometry. They chose uneven ground and built nests at elevations that were just high enough to make them safe from flooding, without being so high they were easy for predators to spot.

Seasonal highlight – Fabulous fungi

The fungi kingdom is home to a wide diversity of species in a staggering array of shapes and sizes. - Credit: Robyn Jay (CC BY-SA 2.0 DEED)

Fungi is a taxonomic grouping (kingdom) of multicellular organisms, distinct from plants, animals, bacteria, etc., that is thought to comprise as many as four million species worldwide. There are various anatomical features that set fungi apart from other organisms, and one in particular is the presence of a structural polymer, chitin - also found in the hard exoskeletons of insects - in their cell walls. The cell walls of plants, for example, contain cellulose, while protozoa and animals don't have cell walls. Older biological textbooks tended to group the fungi with the plants, but they are now considered sufficiently distinct to be classified into their own kingdom, and a study published in 2008 suggested that fungi are actually genetically more closely related to animals than to plants.

There is no single, universally accepted classification scheme for the fungi, and mycologists (folk who study fungi) have varying ideas on the relatedness of these organisms. Nonetheless, fungi are typically divided into five main groups (phyla). Members of two phyla in particular, the Ascomycota and Basidiomycota, grow sufficiently large to be noticeable to most of us. The Basidiomycota contain most of the best-known fungi, including the mushrooms, toadstools, puffballs, stinkhorns, earthstars, etc., while the Ascomycota is somewhat less diverse but includes earthtongues, cup fungi and truffles. There are a number of differences between these two groups, but the main descriptive feature is the manner in which they reproduce: Basidiomycetes produce spores on the outside of club-shaped cells called basidiums, while Ascomycotes (“spore shooters”) produce spores inside club-shaped cells called ascuses.

Quite how many species of fungi there are in the UK is a matter of debate; one recent catalogue of the larger British fungi lists just over 4,000 species, but if you include all the microscopic rusts, smuts, mildews, etc., then the number rises into the tens of thousands. Indeed, most references suggest that there are about 14,500 species of fungi found in the UK (probably a conservative estimate) and we're fortunate to have about 2,700 of them here in the New Forest. Some species grow only in association with particular tree species, or in specific soil conditions, making them nationally rare, and there are currently 380 species of British fungi on the Red Data List.

Form and function

When most people think of fungi, they probably picture a mushroom or toadstool (different words for essentially the same structure, although often used to refer to edible and poisonous fungi, respectively), and consider them seasonal organisms. The reality is quite different. The mushroom or furry aggregation that we see, and in some cases eat, is the fruiting body—whose purpose is to produce and distribute spores—and is only a small part of the fungus that we see when it reproduces. The bulk of the organism is present year-round in the substratum (wood, soil, humus, etc.) and consists of a large web of microscopic cotton-like threads called hyphae, often covering several miles; the whole web of hyphae making up a single fungus is called a mycelium.

A quick sketch showing the basic anatomy of a generic mushroom. - Credit: Marc Baldwin

The hyphae branch out into the substratum and the long, thin hyphae allow it to absorb nutrients and water across its entire surface area. Indeed, fungi have no chlorophyll and cannot photosynthesise to produce carbohydrates (food) as plants do. Instead, most fungi are saprotrophs: they attack and digest plants and animals (living or dead). A few species enter a symbiotic relationship (known as a mycorrhizal association) with certain plants; the hyphae invade the root systems of their host, stealing sugars from their circulation. In return for the stolen sugars, the fungi act as an extension of the plant's root network, allowing it to take up nutrients from a much wider area than it could manage on its own. It has been estimated that some 95% of plant species (including most trees and orchids) form mycorrhizal associations with fungi.

During the autumn, the mild and wet conditions prompt the modification of either individual hyphae or sections of the mycelium (depending on species) into the fruiting bodies that we know as mushrooms or toadstools. The fruiting body expands quickly (it doesn't technically grow), often in a matter of hours. The hyphae become modified into a button-like structure called a hymenophore and, when conditions are right, the fruiting body absorbs moisture and air from the environment, causing the cells in the tissue to expand under the pressure, and the fruiting body inflates. The hymenophore of many species is covered with a thin membrane called a hymenium (or universal veil), which is torn as the fruiting body expands; the remnants often remain as a 'skirt' around the fungi's stem and, as in the case of the fly agaric, pieces may stick to the cap (these are the white spots). The spores are released from gills or veins (depending on species) on the underside of the fruiting body's cap; these structures need to be aligned correctly, so they run parallel to the ground (allowing the spores to drop under the influence of gravity) and the fruiting body can realign the cap by bending the stem as it inflates, as frequently demonstrated by species growing from vertical surfaces, such as the Terracotta hedgehog fungus (Hydnum rufescens). This ability to realign allows fruiting bodies to grow regardless of the surface's orientation. For many fungal species, it is only through microscopic study of the spores that the species can be accurately identified - each species has spores that are uniquely patterned, or uniquely coloured, or undergo specific chemical reactions.

Fly agaric (Amanita muscaria) fruiting bodies in the New Forest. The white blotches (or scales) on the cap are fragments of the universal veil that have stuck to the cap as the fruiting body expanded. - Credit: Marc Baldwin

Perks and problems

Most people are aware that fungi can be important pests of crops, particularly smuts, rusts and moulds. Smuts, from the German word for 'dirt', infect various crops but are particularly problematic for members of the grass family and commercial crops such as maize, wheat and barley. Rusts are plant diseases caused by fungi belonging to the order Pucciniales, which contains an estimated 7,000 species. Rust appears as a peppering of red-brown blotches, typically on leaves but sometimes on stems, that resemble the oxidation of rust seen on iron. Most of us are familiar with the mildews and moulds that grow on spoilt food, and it is the Mucorales (pin moulds), particularly Rhizopus stolonifer, that commonly infect bread and fruit. Fungi can also infect animals, including humans, and ringworm is one such commonly encountered fungus; in humans this often caused by the Trichophyton fungi and manifests on the feet, where it is referred to as athlete's foot.

Despite the potential problems they can cause, fungi also have much to offer humanity. The commonly prescribed antibiotics collectively known as penicillins are derived from the fungal mould Penicillium sp., discovered following a fortuitous incidence of poor hygiene in Alexander Fleming's lab in September 1928. Furthermore, the fungus Penicillium griseofulvum produces the anti-fungal compound griseofulvin, which it manufacturers to stop other fungi muscling in on its space, used to treat ringworm (fungus) in humans and other animals. Perhaps the most significant role fungi play is as recyclers in the ecosystem. More recently, the lion's mane fungus (Hericium erinaceus) has shown anxiolytic (anxiety-reducing) effects in mice, and while there are no clinical data yet, scientists are investigating its potential as a treatment for neurodegenerative cognitive disorders such as Alzheimer's disease. Indeed, for about 90 million years after the evolution of the first primitive trees, Earth was a hotbed of coal formation. During this time, when the trees died, they laid where they fell - often being buried and subjected to the considerable temperatures and pressure that lead to fossilisation - because nothing currently on Earth was able to break down the tough structural compound lignin in the woody tissue.

Lion's mane fungus (Hericium erinaceus) has widely been used in traditional medicines and recent pre-clinical trials suggest it may offer a potential treatment for dementia. - Credit: Marc Baldwin

Around 300 million years ago, at the end of the Carboniferous, this changed, and coal production slowed significantly. A study published in the journal Science during 2012 by biologists at Clark University in Massachusetts sequenced 31 fungal genomes (genetic profiles) and applied them to a molecular clock analysis. (Basically, the molecular clock theory suggests that genes pick up mutations at a relatively predictable rate, like trees accumulating growth rings each year, and counting them allows you to estimate how old a gene is.) The researchers found that an ancestor to modern-day white rot fungus (those of the Agaricomycetes class) evolved lignin-busting peroxidase enzymes about 290 million years ago, allowing them to break down wood. This study builds on a theory proposed by Jennifer Morrison and her colleagues back in 1990, which suggested that the evolution of wood-eating fungi was part of the reason why carbon burial reduced at the end of the Carboniferous, and why Carboniferous forests hadn't rotted away like modern forests do.

Lignin is a complex irregular polymer (i.e., a compound made up of tough crosshatched carbon-based molecules), the structural strength of which allows trees to grow so tall and provides wood with a resistance to rot. We're only just learning precisely how fungi manage to break this polymer down; the fungi cannot take it through their cell walls to pull it apart like they do other compounds, so it seems that they release peroxidases and other reactive molecules that oxidise (physically break apart) the lignin in situ. With the lignin out of the way, the fungi feed on the cellulose in the cell walls of the woody tissue. The crumbly brown logs left behind by the fungus are the remains of the lignin 'skeleton', with the cellulose having been extracted by the fungi. Regardless of the mechanism, it is fair to say that, without fungi, very little of the dead wood in our forests would be recycled and valuable nutrients would remain locked up.

To eat or not to eat?

Many fungal species produce poisonous substances, collectively known as mycotoxins, although why they do so is still a matter of debate given that they don't appear to be necessary for feeding or growth. It has been suggested that the mycotoxins weaken their hosts, which may improve the growing conditions, and some of our most powerful anti-fungal medications have come from fungi, suggesting that some species use these mycotoxins to kill other fungal species, thereby reducing competition. It also seems probable that the presence of these toxins could be aimed at preventing fruiting bodies being eaten before they have had chance to drop their spores. Some species, known as milk-cap fungi (Lactarius), appear to exude milk when damaged. In fact, what they're actually excreting is a milky-white latex, which has evolved to plug holes in the fungal cap and deter predators as a similar self-defence mechanism.

Many fungal species are edible and mushrooms are widely used in food, where they provide a source of protein. - Credit: Nathanael Coyne (CC BY-NC-ND 2.0 DEED)

Some mycotoxins can be destroyed by heating, meaning that certain fungi are only toxic to humans until cooked, while others remain toxic even when dried or cooked. Mycotoxins typically attack the kidneys and liver, resulting in symptoms similar to food poisoning (e.g., sweating, vomiting and diarrhoea). Certain fungi produce more dangerous compounds than others, with members of the Amanita genus of agarics being the most toxic. Two agarics in particular, the death cap (Amanita phalloides) and the closely related destroying angel (Amanita virosa), are the commonest cause of mushroom poisoning in Europe. Some estimates suggest that the agarics as a group are responsible for 95% of the fungi poisoning of humans globally, with 75% of those attributable to phalloides and virosa.

Two groups of toxins, amatoxins and phallotoxins, are believed responsible for making the agaric fungi poisonous, and death caps are known to contain at least six related phallotoxins and five amatoxins. Phallotoxins are generally less toxic and produce the gastrointestinal symptoms, while the more dangerous amatoxins cause significant damage to the liver and kidneys. The specific mechanisms of how these toxins operate, fascinating though they are, are outside the scope of this summary, but as an example, α-amanitin interferes with an enzyme in the liver and stops protein production, which causes the cells in the liver to die and the organ to fail. Hence, following consumption of the death cap fungi, a liver transplant may be your only hope.

Generally speaking, the consequences of eating a poisonous fungi depend on the species, the amount consumed and the speed with which medical treatment is administered. Consumption of very small amounts often involves severe stomach cramps and vomiting, but the prognosis is optimistic. In the case of agaric poisoning, treatment almost immediately after ingestion offers a 90% survival, while delaying treatment for 60 minutes reduces the chance of survival to 10-50%. Unfortunately, most people don't realise they've eaten a toxic fungus until it's too late.

By and large, the safest option for most of us is to stick to buying mushrooms from a reliable source and not to eat fungi that we come across in woods, parks and gardens. Once you get the hang of identification, and with the aid of a good reference guide, you can learn toxic fungus from edible with certainty, but fungal identification can be something of an acquired skill and getting it wrong can be fatal. The best option is to go out on a 'fungal foray' with your local Fungus Recording Group or local Natural History Society.

For a round-up of Britain's seasonal wildlife highlights for mid-autumn, including the red, fallow and sika deer ruts, check out my Wildlife Watching - October blog.

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