Thursday, October 29, 2009

The Magic of Mushrooms

These are the radiating gills of the toadstool known as weeping widow Lacrymaria velutina. For more about this toadstool, visit

The surface layer of the gills, known as the hymenium, produces thousands of spores, and for these to be successfully released into the airstream the gills must always be vertically aligned, so they are very sensitive to the force of gravity and quickly realign themselves if the stipe of the toadstool bends away from the vertical and tilts the cap.

Here, at a microscope magnification of x40 you can see the spores lining the surface of the gills....

...and here, at a magnification of x100 you can see that each is shaped like a small brownish-black lemon..

The spores are formed in groups of 4 on a cell called a basidium, attached to it by short stalks, seen here at a magnification of x400 under the microscope....

... and these appear to be two basidia where the spores are beginning to form. When they're mature and drop off they'll fall vertically down the gaps between those parallel, perfectly vertical gills and will be wafted away in the airstream

If you cut off a toadstool cap, turn it gill side down on a piece of paper of contrasting colour to the spores and leave it in a warm room where there are no draughts for a couple of hours, the falling spores will produce a beautiful spore print..... this

Friday, October 16, 2009

Golden Algae

Forty years ago, when I was a university student, life – more specifically, cataloguing life – was relatively simple. Living organisms fell into one of five kingdoms: bacteria, plants, animals, fungi ................and protists, which were a rag-bag of mostly small organisms that no one knew enough about to be able to fit them into any of the other four categories. The science of classifying living organisms and understanding their evolutionary relationships has moved on, thanks to our ability to look at species’ relationships by comparing their DNA sequences.......which has made classifying life more intriguing and much more complicated. Those rag-bag protists are now subdivided by biologists into several kingdoms, one sub-division of which contains this lovely little organism, less than a millimetre long and called Dinobryon, which is known as a golden alga (or Chrysophyte). There are now thought to be about a thousand different Chrysophyte species, mostly single-celled, but this is one of the more complex types. They all have a golden yellow pigment called xanthophyll, which you can just about detect in the top photo of Dinobryon. This organism, which is common around pond and lake edges, consists of individual cells, each with a couple of lashing flagellae (which you can just about make out poking out of the uppermost 'vase' in the bottom photo), with each cell encased in a glassy vase and attached to a branching stem. The top photo is taken with polarised light, which generates the lurid interference colours, while the bottom one is taken with interference contrast microscopy, which gives better resolution of the individual cells in their ‘vases’.

Thursday, October 8, 2009

Last of the Summer Whines

Ever had the experience where you get into bed, turn the light out, lay awake for a few minutes then pick up a high-pitched whining in the room – which can only be a mosquito? There’s no alternative but to get up and catch it, because there’s no possibility of going back to sleep in the knowledge that you might become a victim of one of these dipteran Draculas. So having caught it, I thought I’d have a quick look at it under the microscope – and it turned out to be an object of great beauty (double-click images for a better view).
The first thing that strikes you about a mosquito under the microscope is its wonderful eyes, sparkling with a kaleidoscope of iridescent colours, that provide wrap-around vision that’s even more complete than in dragonflies (seen above from above and below from below).
Then there are the antennae. This is a female (and therefore a blood-feeder – the males feed on plant juices), identifiable by those radio aerial-like antennae, which are bushier in males. Mosquitoes find their prey by vision, heat sensing, carbon dioxide sensing and scent, so if you are alive and breathing they’ll find you, even with the light out.

Then, of course, there’s that stiletto-like proboscis........

Seen here (above) in victim’s-eye view

With the lights going on earlier every night, more mosquitoes find their way into houses at this time of year – until the first frosts kill them off. I guess it’s one of the perils of having a garden pond that they can breed in, although water in a forgotten bucket in the corner of a yard will suit them just as well.

I’m not certain of the identify of this species but I think it’s Culex pipiens which according to Keith Snow’s Mosquitoes (Richmond Publishing Naturalists’ Handbooks No. 14) ‘feeds almost exclusively on birds’. So, maybe if I sleep with the budgie in the bedroom I’ll be OK..... although he adds, reassuringly, that adults hatching at this time of year feed exclusively on plant juices and enter buildings only to hibernate. That’s alright then. The budgie can relax.

Sunday, October 4, 2009

Travelling light

This strange object, magnified one hundred times under the microscope, is a single seed of a common spotted orchid Dactylorhiza fuchsii. The lower photo shows a couple of the orchid’s seed capsules, with the dust-like seed laying on the paper below.

Unlike seeds of oak and horse chestnut, which send their seeds out into the world with a large food store surrounding the embryo, orchids have a much more minimalist approach to equipping their embryos for future survival. The orchid embryo – inside the darker object in the centre of the seed in the top photo – has no food store and is housed in a fragile papery coat, just one cell thick. The whole seed is no larger than a speck of dust and is so light that it can be swept up by air currents and wafted long distances – orchid seed could easily be blown across the English Channel, for example. So, unlike heavy seeds with a large food that are unlikey to disperse very far from the parent plant, orchid seeds are great travellers heading for random destinations and this accounts for their tendency to suddenly appear in unlikely places – lawns, roadside verges, industrial spoil tips, to name but a few. A large orchid flower spike will produce tens of thousands of these minute seeds, but only a tiny fraction will ever achieve the next critical step in the life cycle – landing on soil that contains the essential mycorrhizal fungus that will link up with the germinating seed and provide the embryo with the nutrients that it lacks until the seedling is large enough to produce leaves and survive on its own. After that the orchid's roots returns the favour by supplying its partner fungus with nutrients for the rest of the orchid's life. Early growth of the orchid seedling is slow and its leaves passes unnoticed - until it's large enough to produce a spectacular flower spike........and to read about the next step in the life cycle - pollination of the flowers - take a look at