Nail Fungus, Poronia punctata, at Buxton Heath.

At the end of April a group of us visited Buxton Heath, just north of Norwich. We had mainly gone to look for insects but it was a cold day with light rain and, apart from some dung beetles, most of the insects we’d hoped to see had sought shelter.

Nonetheless, we had a good walk and up on the drier heath I was very pleased to find something I hadn’t seen before: Nail Fungus, Poronia punctata. It is a very distinctive species, which looks rather like one of those flat-headed nails used to fix bituminous roofing felt to the roof of a garden shed. The First Nature website has some great photographs. The cap of the fungus has distinctive pores, hence the generic name, Poronia.

Nail Fungus appears in autumn but persists through winter into spring. It can be found growing on dung in open areas, such as grassland and heathland, where ponies graze. It is an ascomycete in the family Xylariaceae, and therefore is a relative of Cramp Ball (King Alfred’s Cakes, Daldinia concentrica), which I wrote about last May.

In Britain Nail Fungus grows on pony dung but in other parts of the world it has also been found on the dung of cows, sheep and elephants.

Nail Fungus is a declining species in Britain and throughout the world. At the time of writing it was being assessed for the Red Data List for fungi. Its decline is due to the reduction of natural and semi-natural grasslands and the use of agrochemicals, pesticides and veterinary additives. In her MSc thesis Nicola Edwards studied the fungus at Hockwold Heath and Cranwich Camp in Norfolk, and found that dung needed to be damp enough and have a reasonable amount of dung beetle activity for the fungus to grow (note 1).

Poronia punctata is a UK Biodiversity Action Plan species. The NBN Atlas lists 198 British records and shows its distribution in the British Isles. A century ago it was quite common but it declined until The New Forest in Hampshire was one of its last strongholds. Now that ponies are being used more widely for conservation grazing the species is cropping up more frequently again and it has been recorded from Dorset, Hampshire, Surrey and even London. In Poland, the species was rediscovered in 2016, after an absence of a hundred years.

In Norfolk Nail Fungus was rediscovered in Thetford Forest in 2012, the first record for the county since 1944. It has been seen a few times since then, including by James Emerson at Holt Lowes last autumn (note 2). It was good to have seen Nail Fungus on Buxton Heath.

Nail Fungus is considered to be inedible. Even if it wasn’t rare, Nail Fungus would not be a species for fungal foragers, as it is small and grows on dung. As the First Nature website says: “who would even want to try eating them?“. However, some scientists are interested in the fungus because it contains a number of bioactive compounds, including a group of sesquiterpenes known as punctaporonins, which inhibit the growth of competing bacteria and fungi in dung.

Notes

Note 1 – See “Does Breckland vegetation and its management influence abundance of Poronia punctata?“, Nicola Edwards, MSc thesis, Sparsholt College, 2015.

Nicola found that the anthelmintic drug pyrantel wasn’t detrimental to the fungus, presumably as it didn’t reduce the number of dung arthropods. However, elsewhere, the anthelmintic drug ivermectin has been implicated in the decline of dung beetles, which will presumably have a knock-on effect on Nail Fungus.

I’m glad to say we found good numbers of Minotaur Beetles on Buxton Heath when we visited.

Note 2 – Nail Fungus was plentiful at Holt Lowes when I visited at the end of October 2019.