Wet Willows

Just got back from a holiday in sunny Spain to discover it's pretty wet here in the Adur valley. So on a walk around Woods Mill this afternoon I thought I'd see if I could spot one of my favourites – Amber Jelly Fungus Exidia recisa – on the willows around the pond. I've only seen it a couple of times since I first found it here in the very wet weather we had a couple of years ago (here).

Success! Although I struggled to get a decent photo in the low light.

The wet willows proved to be a pretty rich hunting ground for fungi.

This rather lovely purple thing is the Silverleaf Fungus Chondrostereum purpureum.

Here and there the branches were splashed with yellow.

Andy Overall wrote a very useful article on these 'Yellow Brain Fungi' in volume 18 (3) of Field Mycology [1]. There are two species which look very similar: Tremella aurantia and Tremella mesenterica and I've always been rather confused about how you separate the two.

Andy explaines that Tremella species are parasitic on other fungi or lichens, and the two species mentioned above are specific to different hosts. T. aurantia grows almost exclusively on Stereum hirsutum whereas T. mesenterica grows on resupinate (flat-growing) fungi from the genus Peniophora.

I've looked for a host fungus when I've found 'Yellow Brain' in the past and never been able to find any sign of it. In another paper on these species, which Andy references [2], Peter Roberts notes that T. aurantia "seems to enter the host fruit body whilst it is still developing, so that no external host normally remains" and T. mesenterica "appears to parasitise the mycelial hyphae rather than the fruit bodies of the host." So I don't feel so bad now about not being able to find the host.

Peter goes on to say that, "Often T. mesenterica can be found growing on the upper surface of a twig with the Peniophora producing fruit bodies on the underside".

I hunted around near where this 'Yellow Brain' was growing to see if I could find any sign of a host. I found this, a short distance away on the same branch.

Could this be a Peniophora? I'm rather intrigued by it, whatever it is, as the ashen-grey crust appears to be dotted with red blobs.

Both papers say that the two 'Yellow Brain' species can be separated with microscopy and there are some nice illustrations in Peter Roberts' article, so I feel like I should have a go.

Reproduced from Roberts, 1995.

Wish me luck!

UPDATE 09/01/2018

Taking a tiny slither off the outside of that 'Yellow Brain' I was surprised to discover this tangle of threads (hyphae?) as well as the anticipated blobs (basidia? spores?).

100x magnification. Mounted in water.

I'm still getting the hang of using my new eyepiece camera so I was really pleased to find - amongst all that chaos - something which looked just like illustration 7 above: a basidium! The line down the middle shows it is 'septate'.

400x magnification with zoom.

I had a harder time finding the spores, but I think this is one:

Can't remember what magnification this was.

I'm not 100 % sure I've got the calibration sorted on the eyepiece camera, but I think I made this spore around 12 microns x 9 microns, which is in range for T. mesenterica (which has bigger spores than the other one).

I was struggling to see features clearly when mounted in water, so I thought I'd try them with a stain. I opted for PlaqSearch which I've been told is a safe, general-purpose stain.

Yup! That works!

With everything stained this shocking pink colour, it was easier to spot those blobs with dangly bits on which look like a good match for T. mesenterica basidia.

These microscopic features seemed to have a lot of personality. But I felt like they were missing something... Googly eyes!

If you squint at this image, I think you can make out some clamped hyphae.

And I found these quite hard to find, but I think this image shows 'conidiophores' (whatever they are; bottom of illustration 8, above).

400x magnification. Mounted in water; stained with Congo Red.

I think this information is sufficient to confirm my collection as Tremella mesenterica. Need to keep an eye out for the other one now!


For the record
Date: 6 January 2018
Location: Woods Mill
Grid reference: TQ219134

Record entered into FRDBI 07/09/2018

1. Overall, A. 2017, Tremella aurantia & T. mesenterica, two British 'Yellow Brain Fungi' compared, Field Mycology Vol. 18 (3), 2017
2. Roberts, P., 1995, British Tremella Species I: Tremella aurantia & T. mesenterica, Mycologist Vol. 9, Part 3 https://doi.org/10.1016/S0269-915X(09)80270-X