Tuesday, December 24, 2013

Downsizing Christmas

I germinated this spruce tree from a seed that was sent to me eight years ago, with the intention of growing it as a bonsai specimen. This year it's finally big enough to cope with some Christmas decorations. If I'd planted it in the garden it might eventually have grown to about 50 feet tall; as a bonsai it's unlikely to grow to much more than a couple of feet, but it'll be a family Christmas tree that I can hand on to my children. Once Christmas is over it will get some careful  pruning and training.

Best wishes for a Happy Christmas to all who have visited and commented on this blog throughout 2013.

Wednesday, December 18, 2013

Beeching's Legacy

Thursday's Guardian Country Diary describes a walk along a section of disused railway line between Romaldkirk and Cotherstone in Teesdale, which now forms part of the Tees Valley Railway Path.

When I was a kid I went to school on the train every day. I travelled on electric trains but those were still the dying days of steam and I can still recall the sound and the smell of steam locomotives like these thundering through the station while I waited for my sedate electric train to arrive. Along with my mates I often stood on the footbridge while the fire-breathing, steam-snorting monsters passed underneath.

The mainline steam trains are now a distant memory - and so are many of the rural railways that were axed in the Beeching closures in 1963.

This is what the rail network looked like before Beeching ......

...... and this was what remained when he'd finished his work.

But it's an ill wind that blows nobody any good, and many of the old railways lines whose tracks have been lifted are now excellent footpaths that pass through some spectacular countryside and have often become unofficial nature reserves. 

Here are some pictures of some fine local examples:

The Tees Valley Railway Path photographed in high summer this year.

A wonderfully festive hawthorn berry crop along the route this winter ...

..... with plenty of holly - Cotherstone village is in the distance.

This is a cutting along the Tees Valley Railway Path near Romaldkirk earlier this year, in February. Drifting snow that filled railway cuttings often brought trains to a standstill when lines like this in the Pennines were still in use.

The footpath along the old railway line that runs through the nature reserve at Smardale Gill in Ravenstonedale, Cumbria ....

.... where the Smardale Gill viaduct carries the line through the limestone grassland.

This is the same line, but this time on the eastern side of Kirkby Stephen, where the line travelled eastwards across the notorious Stainmore Summit - the highest railway in England.

The line east of Coxhoe in County Durham, with magnesian limestone embankments rich in wild flowers and butterflies.

And finally, the railway path through the Derwent Country Park near Gateshead, where you can walk on the track bed of the old Derwent Valley Railway through woodland to the Nine Arches viaduct and watch red kites soaring overhead.

Saturday, December 14, 2013

More bathroom biodiversity: the Celibate Rotifer

A few days ago I posted some pictures of tiny animals called tardigrades that I found living in the wet mould growing on our bathroom window. 

They weren't the only wildlife that I found there; when I looked at two more pinhead-sized samples of the mould under the microscope theycontained several of these bdelloid rotifers. These are about a quarter of a millimeter long and are truly extraordinary animals.

Bdelloid rotifers consist of an elogated body containing complex internal organs. Normally they are anchored by their tail and when at rest they extend a pair of organs on their head that form the corona, each with a circle of cilia. The  cilia are anchored but because they beat rhythmically it appears as though they rotate - which is why the paired structures are sometimes known as wheel organs. 

The beating cilia create a vortex in the water that draws small food particles into the rotifer's mouth - click here to view a couple of movies which illustrate this far better than words can.

One peculiarity of bdelloid rotifers that intrigues biologists is that they never undergo sexual reproduction; they reproduce clonally and have done so for around 80 million years. 

It's generally assumed that sexual reproduction evolved because it generates offspring that are genetically different from their parents, which is beneficial in a constantly changing environment; somewhere amongst the genetically variable population there are always likely to be some that are better equipped than others to deal with new challenges, like changing climate or new diseases. 

Clonally reproducing organisms, like these rotifers, are all genetically identical so they should all be equally susceptible to change or disease and would be prone to extinction. So how have these rotifer clones managed to survive after 80 million years of celibacy?

The answer seems to be that they can incorporate DNA from their food - which consists of fungi, algae and bacteria - into their own DNA, so generating genetic variation in their population. Like tardigrades they are very drought-resistant and when their surroundings dry out they form a tough, durable cyst. 

When the cysts hatch again and rehydrate breaks develop in their DNA molecules that would normally be fatal, but DNA from their partially-digested food is used to repair these, so about eight per cent of rotifer DNA actually comes from fungi, bacteria and algae. It gives new meaning to the old  saying "you are what you eat".

You can see partially-digested food (most likely mould from our bathroom window) inside this rotifer's gut.

Rotifers like this are ubiquitous. Their durable eggs are transported by water and wind and they hatch anywhere that is moist. Mosses are habitats where you can find them in very  large numbers. If you keep cut flowers in a vase you can almost guarantee that there will be a large population of rotifers living on the submerged stems within a week. 

This is a higher magnification image that shows the corona, where you can just make out those beating hairs ....

 ..... and these are the jaws (the mastax) in the neck of the animal. They chew constantly. Here they are open ....

.... and here they are closed.

There's one other amazing property of rotifers that sets them apart - they are more resistant to radiation than any other animal. Tests have shown that they can survive doses of radiation that are 100 times greater than would kill a human, which means that when there are nuclear reactor accidents these will be last animals to succumb. This again is probably due to the unusual ease with which they can repair breaks in their DNA.

It's amazing what you can find in your bathroom. I wonder what's lurking behind the sink................

For pictures and information about some more rotifers, click here.


Gladyshev, E.A., Meselson, M., Arkhipova, I.R. (2008). Massive Horizontal Gene Transfer in Bdelloid Rotifers. Science, 320, 5880

Gladyshev, E., Meselson, M. (2008). Extreme resistance of bdelloid rotifers to ionizing radiation. Proceedings of the National Academy of Sciences 105 (13), 5139-5144

Jean-Francois Flot et al (2013) Genomic evidence for ameiotic evolution in the bdelloid rotifer Adineta vaga. Nature 500, 453–457

Wednesday, December 11, 2013

A bit of a stink

Few of our native wild flowers have such beautiful fruits, but such an unpleasant name, as stinking iris Iris foetidissima. I grew some plants from seed a few years ago and planted them in dry sandy, sun-baked soil under our garden hedge, where they've thrived ever since and produce these lovely seed capsules that open in late November to reveal their spectacular seeds.

Two other common names, gladdon and roast beef plant are also in common usage and the latter refers to the smell of the crushed leaves that have a powerful aroma of beef (though to me they smell more of roast beef-flavoured crisps, rather than the real meat). In The Englishman's Flora Geoffrey Grigson listed no less than seventeen further common local names used in various parts of the British Isles. A proliferation of such names for a plant is usually a sign that people once found it useful and gladdon has a long history of applications in herbal medicine, mentioned by Dioscorides, William Turner and John Gerard in their herbals. One popular use was as a purgative, made from a decoction of gladdon root and beer.

In his Botanical Arrangement the 18th. century doctor and botanist William Withering, always a good source of contemporary anecdotes, mentions that "the juice of the root of this species is sometimes used to excite sneezing; but it is an unsafe practice, violent convulsions sometimes having been the consequence."

I rather like the flowers that are unspectacular and reminiscent of faded denim, but Withering wasn't so impressed, describing them as being "of a disagreeable purplish ash colour", also mentioning that in his day there was also a variegated-leaved form which now seems to have disappeared from cultivation.

Saturday, December 7, 2013

Biodiversity in the Bathroom

There can't be a bathroom in Britain where steam doesn't sometimes condense on cold windows at this time of year - and wherever moisture accumulates around window frames bathroom mould is sure to grow, unless you dry the windows very thoroughly every morning. 

So while I was laying in the bath yesterday I wondered what the mould looked like that I could see was beginning to grow in the corner of the uPVC window frame, and today I scraped a tiny amount off - about enough to cover the head of a pin - and had a look at it under the microscope at x 40 and x100 magnification. 

The fungal hyphae were pretty uninteresting but the animal life that was living amongst them was fascinating, and included three of these ....

..... delightful little tardigrades.

Tardigrades are minute but complex animals that are also known as water bears or, in the US, moss pigs. Most of them live in mosses, stabbing moss cells with mouthparts that resemble aphid stylets and then sucking out the cell contents. 

These three, that were about a fifth of a millimetre long, must have been feeding on the bathroom window mould. If there were three in the tiny sample that I collected, there must be vast numbers on houses where the fungus is allowed to grow unchecked around condensation-soaked window frames.

These are lively little animals with a brain, complex digestive organs and two eyes.... 

.... that you can see in this higher magnification view. The arrow-shaped structure between the eyes is the stylet, used for feeding, with a muscular pharynx at its base.

Tardigrades have eight stubby little legs, each equipped with a pair of claws that are visible on the end of one leg in this image. This makes them particularly adept at clambering through the branches of a forest of mosses - or through the fungal hyphae of bathroom mould. 

You can find a wonderful scanning electron microscope image of a tardigrade by clicking here and a long article in American Scientist on these fascinating animals by clicking here.

So how did they arrive in the bathroom? Almost certainly via their minute eggs which are carried everywhere on the wind. 

These animals are totally harmless but I guess you might find the thought of numerous tardigrades crawling around wet window frames as either fascinating or disgusting; if it's the latter and you are about to rush off and douse your windows in disinfectant, just ponder this. 

When dry conditions prevail, tardigrades survive  by producing drought resistant eggs that are amongst the most indestructible living organisms on the planet. When they are in the egg stage (known as the tun stage) they can survive immersion in boiling water and liquid nitrogen and can survive for decades before they hatch again. Your disinfectant won't have much effect on the eggs, even though it'll kill the adults.

But, most remarkably, these are the only multicellular animals that have ever travelled in outer space without a space suit and survived, when they were flown as tuns in the Space Shuttle - a feat that no human will ever equal. They deserve some respect. For a detailed account of their adventures in outer space, click here and here.

Something I'll ponder when I'm  laying in the bath tonight and watching the condensation trickling down the windowpane.

You can find some more pictures of tardigrades, this time extracted from mosses on our garage roof, by clicking here.

Wednesday, December 4, 2013


Thursday's Guardian Country Diary is about two separate populations of starlings that inhabit the seafront at Whitburn, near Sunderland. One flock, usually of about 100 birds, is often to be found either on the shore amongst the strandline seaweeds at low tide or at high tide feeding on a patch of grassland on low cliffs at the north end of the beach. They exhibit all the 'normal' starling behaviour and are very easily spooked - they spend a lot of time in flight but when they do settle they don't stay grounded for very long - when one bird takes to the air the others always follow.

Further to the south along the seafront this little group, of around a dozen birds, has adopted a completely different life style, forsaking the panicky behaviour of the flock and .....

.... instead spending their time on the promenade, oblivious to cyclists, dog walkers and passers-by and focusing all their attention ....

.... on promenaders who buy fish and chips from the shop across the road and sit and eat them leaning against the sea wall. They're waiting for someone to throw them a chip and they usually beat the resident herring gulls to the prize.

Despite abandoning the collective paranoia of the flock in favour of a life of cadging fast-food, this streetwise splinter group is in fine fettle - life on the streets suits them well - and they are clad in immaculate early winter plumage.

Unlike the flocking birds at the far end of the promenade, this individual was completely fearless, maybe expecting me to throw it a chip in return for a photo-opportunity.