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A missing Western Australian ‘Death Cap’ Amanita?

I was interested to read about some people in Rwanda who eat large quantities of a mushroom from the genus Amanita that grow in the Eucalyptus plantations there. This mushroom is called Amanita bweyeyensis. There is a YouTube video on the subject, from which this image is clipped.

Peeling Amanita bweyeyensis before consumption


https://www.youtube.com/watch?v=PtjRvTmg3GY

This mushroom sits within the Phalloideae section of Amanita, where the deadly species containing amatoxins reside. Despite this, it does not contain amatoxins nor phallotoxins. It is the amatoxins that are the cause of many fatalities when people eat other mushrooms in this section such as Amanita phalloides. Phallotoxins are not orally active so pose less of a threat.

DNA analysis shows that this mushroom sits within a small cluster that includes the white “death cap” mushrooms from Western Australia. These are: A. djarilmari, A. eucalypti, A. gardneri and A. marmorata. The partial phylogenetic tree is from this paper: https://mycokeys.pensoft.net/article/34560/zoom/fig/11/

Analysis of the Western Australian species has shown that these do not contain amatoxins either. This is reported in a paper that is behind a paywall but the precis is shown at this link.

American Amanita expert Debbie Viess advises that these mushrooms would be called ‘Destroying Angels’ rather than ‘Death Caps’ according to US word usage.

This is a picture of the Amanita bweyeyensis from the paper mentioned above. Unfortunately, I can’t show pictures of the Western Australian species.


Since the African species sit so close to the WA species in terms of genetics and they grow in Eucalyptus plantations, it is tempting to think that they might have their origins in WA. If this is the case, they do not seem to have been recorded here. It is hard to know where the Eucalyptus trees planted in Rwanda came from originally; they are not WA natives but it is not beyond the realms of possibility that they came from Western Australia, given that this is the closest state to Africa.

This brings to mind the green Russulas that grow in the Eucalypt plantations in Madagascar which are eaten by the people there. They also peel those mushrooms before consumption. These Russulas are unknown in Australia though it would seem likely that is their origin.

How are amatoxins produced?

The production of amatoxins has been investigated in some detail by Heather Hallen and others in terms of genes. It has been shown that the amatoxins originate from proproteins synthesised on the ribosome. The function of the ribosome is shown in this rather cute image which is by SITNBoston and is taken from the Harvard University Site.

The codon carried on the mRNA (we all know what this is these days!) is decoded in the ribosome and amino acids carried by tRNA are converted into an amino acid chain which is known as a proprotein. This is similar to the process by which the covid spike proteins are produced by the mRNA vaccines.

These proproteins have a size in the range of 34 to 35 amino acids whereas the toxins have a size of 8 amino acids. In order for the amatoxins to be produced, these long chains need to be reduced in size and the fragments cyclised. This process has been studied in the amatoxin-producing genus Galerina by a group of researchers and the process is shown in this image from that publication.


The proproteins are acted on by the prolyl oligopeptidase enzyme which cuts the chain at the Proline amino acid and then stitches together the piece that is clipped out to form the bicyclic polypeptides (2 rings of amino acids) that we know as amatoxins.

The amatoxins are bicyclic (=two rings) octapeptides (=contain 8 peptides) with C-to-N (head-to-tail) condensation of the peptide backbone and a cross-bridge between Tryptamine(Trp) and Cisteine (Cys). Three of the amino acids (Trp, Pro, and Ile) are hydroxylated. Phallotoxins are similar in structure but their macrocycles comprise only seven amino acids. The relationship between the different amino acids is shown more clearly in this labelled diagram.

The image below shows a 3D view of an amatoxinA molecule in a similar orientation to the image above. The yellow sulfur atom can be seen within the structure and the 5-membered nitrogen-containing hetercyclic ring of (hyroxylated) Proline (P) seen on the left hand side with the (hydroxylated) Isoeucine (I) skeleton above it and Asparagine(N) below it. There is also a bridge with the (hyroxylated) Tryptamine sitting in the middle of the structure which is facing out into the page.

Amatoxin A molecule

This type of structure is very stable and survives heating and the action of digestive enzymes. That is one of the reasons that this type of toxin is so dangerous.

Just why this group of mushrooms does not always produce these toxins doesn’t seem to be well understood. I am informed by Debbie Viess that specimens of Amanita marmorata taken from the same region have tested positive in one case and negative in another.

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Amanita rubescens – The Blusher – an introduced species

The early colonists of Australia were mainly of British origin and they brought with them the trees with which they were familiar.  Such trees include pines and oaks.  With these trees came the fungi that were associated with the roots of the trees.  There are quite of few of these fungi that have now become established in various areas in Australia.  One of these is the infamous Death Cap, Amanita phalloides.

Because of the lethal consequences of eating Amanita phalloides, people have a natural caution about eating anything in the Amanita genus.   This includes some of the most enthusiastic mycophagists, including myself.

I had not been aware of any edible Amanitas in Australia until I heard of Amanita rubescens.  It occurs in the Adelaide hills and in Queensland and probably in places in between.  My encounter with it was in the Adelaide hills.  It was growing in a park filled with oaks and pines and in this case I believe it was growing on the oaks.  Here is what it looks like in its various stages of growth.

rubes

Amanita rubescens at various stages of growth.

Some important general features are the lack of a volva at the base and the presence of ‘warts’ on the surface of the mushroom.  When it is broken open or cut, the white flesh and gills take on a red/pink colour as shown in the next picture.

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Amanita rubescens showing red bruising

There are not too many mushrooms that this could be confused with.  The main one that crops up in the literature is Amanita pantherina.  A distinguishing feature of A. rubescens that sets is apart from A. pantherina is the presence of striations on the annulus.  These are shown in the picture below. You can also see the pink colour of the broken flesh of the cap there.

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Striations on annulus of Amanita rubescens

This mushroom is known to contain a toxic, haemolytic protein that is destroyed by cooking.   This in mind, I cooked some up on a barbecue until they were quite soft.  In fact they were so soft that they did not really appeal much.  This being my first taste of a new mushroom, I tasted the cooked material without swallowing it.  The taste reminded my a bit of Volvopluteus.   I have read reports that it is better cooked hard until it starts to brown.  This is the case with many other mushrooms.

It is scary eating an Amanita for the first time.  People who I know and respect regarding edible mushrooms in Australia cannot bring themselves to eat this one.  My caution was brought into sharp focus the next morning when I felt decidedly ill.  I don’t actually think that this was the mushrooms, as I had felt a little ill the night before with food from the place where I was staying.

I will try this again, next time with hard cooking.

I would like to thank my friend Kate for giving me the heads up about these.  You can see her interesting site about foraging  here. She is in South Australia and really knows her mushrooms.

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Lactarius deliciosus – Saffron milk cap – an east coast favourite.

The Saffron milk cap is a mushroom that occurs widely on the east coast in pine forests.  Foragers are actively encouraged to pick this mushroom in NSW in places like Oberon.  It also occurs in Victoria, South Australia and Tasmania.  Reports from Queensland are rare but it is occasionally found there. Sadly, it is not something we see in the pine forests of WA, though there have apparently been unsubstantiated reports of it from the Kewdale area, according to Bougher and Syme (1998).  There is another mention of someone trying to establish this in WA in an earlier paper. I have certainly never seen it in WA.

To view one of these beauties I had to travel to Adelaide on a heads up from some friends there.  These were cropping up in early February of 2017 after some rain, to the general surprise of enthusiasts there.  There were not a lot of them at this time, but I did manage to find this single specimen, to my great joy.  Thanks to Kate et. al. for the heads up!

This is what it looks like from the top.  Notice the pine needles.

saffie
Lactarius deliciosus cap

When cut, the inner surface reveals an orange colour at the margins, as shown below.

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Lactarius deliciosus showing red cut surface

Some texts say that these mushrooms are not particularly good eating and that the name is in fact a misnomer.  To test this out, I took my specimen down to a the barbecue at a local park in suburban Adelaide and fried it up with a little olive oil.  Adelaide is so well endowed with such parks and barbecues and I am sure that they are a popular gathering place. On this particular day however there was nobody else around though, and perhaps that is because it was 42 degrees. All this reinforces the oddity of finding mushrooms at this time of year.

Anyway, back to the taste test.  I found that the smell and the taste were intimately entwined and that it was a pleasant and unusual taste.  It is hard to describe a smell or taste but I kept thinking of vegetables like carrots.  This may well have been influenced by the orange colour.  The other very distinctive and great thing was the firmness. This is easily the most firm mushroom that I have ever cooked and eaten.

I look forward to eating more of these.  Who knows, perhaps they might crop up in WA?  Time will tell.

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Laetiporus portentosus -White punk, poor tucker indeed

There have been many reports from the times of early European settlement, all from Tasmania, of the Aboriginal people eating a white’ punk’ growing on trees.  It has been widely assumed that this is Laetiporus portentosus, formerly known as Piptoporus portentosus.

This June I chanced upon a specimen of this lying on the ground in Bridgetown.  It was quite a massive thing, weighing several kilos and it was saturated with water.  That is why I assume was on the ground, having fallen from its position because of its weight.  Here it is sitting on my dining room table.

Laetiporus portentosus desk

Fallen Laetiporus portentosus on table

 

Here is another shot of it, this time showing the inside after I had cut it open with great difficulty.  I don’t think this would have been possible with primitive tools.

Laetiporus portentosus cut

Laetiporus portentosus cut open

You can see that the inside looks sort of cottony.  In fact it more closely resembles polystyrene in texture.  An attempt to eat a small piece of it revealed that it was about as edible as polystyrene too.  Not even in an emergency could anyone possibly eat and digest this fungus.  Perhaps the story is different with very small specimens but I am doubtful.

It is quite difficult to get a picture of one of these in-situ on a tree because they tend to grow quite high up.  I was lucky enough to spot one by a road cutting near Donnybrook that enabled me to scramble up and take a picture with my phone.  Here it is.

laetiporus donnybrook

Laetiporus portentosus in situ

The fact that these are relatively few and far between and so high up on the trees is further evidence against them being used as food.

It is however widely reported that they were used as tinder and to carry fire.  Some experiments revealed that a dried specimen could be ignited very readily and that it would smolder for a long time.  By judicious control of the fire front on a smoldering specimen it could easily be kept aglow for hours.  Uncontrolled burning of half a specimen lasted about 40 minutes.  I made a short video of a small piece smoldering after it had been ignited. A still from that video is shown below.

laetipurus glowing

A piece of Laetiporus portentosus smoldering

 

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