Ridged tooth  (Hydnellum scrobiculatum)

The ridged tooth fungus belongs to the stipitate hydnoid fungi group. Members of this group are also known as 'tooth fungi' (fungi that release their spores from tooth-like structures), and all have a short stalk or 'stipe', hence the name 'stipitate' (7). Young fruit bodies of Hydnellum scrobiculatum have different colours to older ones, as the pale area of growth is broadest in young specimens (4). As they age, the fruit bodies become brown with ridged 'growth zones' that radiate out from the centre (4). Several caps often fuse into one mass, which has a number of stalks that may grow around blades of grass and other objects (4). This species shares many features with the very similar Hydnellum concrescens, which is said to be distinguished by being more distinctly zoned, by the flesh greening in alkali, and by its slightly smaller spores (7).

WARNING: many species of fungus are poisonous or contain chemicals that can cause sickness. Never pick and eat any species of fungus that you cannot positively recognise or are unsure about. Some species are deadly poisonous and can cause death within a few hours if swallowed.

The ridged tooth fungus is widely distributed in the northern hemisphere and has also been recorded from Australasia. It has a wide distribution in England and Scotland, but is scarce (4). In England, many records originate from the New Forest (9), East Berkshire, and the Surrey Commons (1). There is one doubtful record from Wales (8).

Occurs under pine trees in woodland (1), and other trees including broadleaved species (6).

Fungi are neither plants nor animals but belong to their own kingdom. They are unable to produce their own food through the process of photosynthesis, as plants do; instead, they acquire nutrients from living or dead plants, animals, or other fungi, as animals do. In many larger fungi (lichens excepted) the only visible parts are the fruit bodies, which arise from a largely unseen network of threads called 'hyphae'. These hyphae permeate the fungus's food source, which may be soil, leaf litter, rotten wood, dung, and so on, depending on the species. With the exception of the earpick fungus Auriscalpium vulgare, all stipitate hydnoid fungi are ectomycorrhizal species; they form close symbiotic relationships with trees, and derive some of their nutrients from the tree's roots. This aids them in obtaining nutrients on poor quality soil, and means that are always found in association with trees (1).

Hydnellum scrobiculatum is associated with pine trees; this provides an easy, but not necessarily accurate way of distinguishing between this species and H. concrescens, which occurs under chestnut or oak trees (1).

The best time of year to look for the fruit bodies of Hydnellum species is September. Interestingly, all Hydnellum species show very low levels of invertebrate damage; it is possible that they may contain protective chemicals that may also protect them from grazing mammals (1).

The true status of this species is unclear due to the confusion with H. concrescens. If all records of H. scrobiculatum that were made under species other than pine or 'conifer' were discounted, the species would rapidly become one of Britain's rarest Hydnellum species. All species of stipitate hydnoid fungi are vulnerable to the effects of atmospheric pollution (1), soil eutrophication, soil disturbance (e.g. by timber management) and competition from vascular plants (1).

The UK Biodiversity Action Plan (UK BAP) has produced a Group Action Plan for 14 UK species of stipitate hydnoid fungi (2). Much more research on these fungi is needed if they are to be conserved (1). Scottish Natural Heritage has been conducting an extensive survey of all stipitate hydnoid fungi in Scotland (4). Ridged tooth fungus is afforded general protection under the Wildlife and Countryside Act 1981, but it is not one of the four species of non-lichenized fungi given special protection under Schedule 8. The status of this fungus will remain a mystery until some reliable method of distinguishing it from H. concrescens is found. (2)

For more on rare fungi see Peter Marren's article available from Plant Talk On-line:
http://www.kak75.dial.pipex.com/Pages/26fungi.html

Information authenticated by Carl Borges of English Nature:
http://www.english-nature.org.uk/ and by Dr Peter Roberts of Royal Botanic Gardens, Kew:
http://www.rbgkew.org.uk/