Wednesday, January 29, 2014

Mid-winter Pond Dipping

Thursday's Guardian Country Diary is about freshwater invertebrates that remain active all through the winter. There may be no bees or butterflies about at the moment, but there are plenty of aquatic animals to look at - the only problem is that the water is bone-numbingly cold, so collecting them can be a bit of an ordeal! 

All the animals below (except the bottom one) were found in a single jam jar of water, dredged along the edge of our garden pond which had been frozen over on the previous night.

This is a freshwater orb-cockle Sphaerium sp. There must the hundreds of these little bivalves (the largest was about 8mm. across) in our pond. The two pink protruding tubes on the left are the inhalent and exhalent siphons that circulate water over the gills. You can just see the muscular foot protruding through the shell valves in the 5 o'clock position. 

Orb-cockles are surprisingly mobile, especially when they are small. This one, whcih was about 4mm. long, is using its muscular foot (which you can see protruding from the back of the shells) to scoot across the bottom of the container.

There are scores of these red ramshorn snails in our pond but it's providing difficult to identify it precisely. I posted the pictures on the excellent iSpot web site and there are varying opinions as to its identify. It might be Planorbis corneus rubrum or it could be Planorbella duryi which is the American ramshorn snail. Either way it's an introduced species that probably came in with pond weed bought from a garden centre.

If there are scores of ramshorn snails, then there must be many thousands of these flatworms (Polycelis nigra?) in our garden pond - there were over 50 in a single jam jar sample. They glide along like magic carpets, propelled by a covering of beating cilia which you can see on a marine species by clicking here.

Our pond has a thick layer of decomposing leaves at the bottom - perfect conditions for water slaters (aka water hog-lice), so there are large numbers present.

Gammarid shrimps like these prefer well oxygenated flowing water so our somewhat stagnant pond is far from ideal, but there are still plenty present in the shallows and they are very active swimmers, making them difficult to photograph.  Mostly they swim on their sides, or sometimes upside down, curling up when they are alarmed. These have an interesting history - I introduced them from a population that I rescued from the bottom of Wearmouth Colliery before it closed; you can read the details here.

The young gammarids are almost transparent - I think this must be a male, judging from those prominent claws on the front pair of legs.

And finally, this animal (below) is not from our pond. I collected it a few days ago from the gravelly bottom of a ditch, with snow melt water flowing over it, on the edge of the moors at St. John's near Wolsingham in Weardale, and it's ........

...... an exquisite little caddisfly larva, with a tube constructed mostly from quartz grit. They can be coaxed to build their tubes from more exotic materials - for a stunning example, click here

Wednesday, January 15, 2014

Pteridomania and an obsession with mutants

Thursday's Guardian Country Diary describes a fragment of mature old woodland at Wolsingham in Weardale whose fallen, decaying trees support a wealth of wildlife, including ...

..... this rather lovely epiphytic polypody fern that was attached to an oak branch that had been torn off by the gales. The golden structures on the underside are the sporangia, ripe and releasing spores. You can read about the full life cycle of ferns by clicking here and see some more close-up and microscope pictures of the sporangia by clicking here.


Picture by Helen Allingham, originally published in the Illustrated London News July 1871

The golden age of fern popularity was in Victorian times, during a period that has come to be known as Pteridomania. Then the obsession with collecting and growing these plants reached an all-time high, so much so that the population sizes of some native ferns (like holly fern in Teesdale and all the filmy ferns) were reduced to the point where they are now endangered species in our flora. The ladies in the image above are well equipped for digging up choice ferms, although brambles must have played havoc with those dresses.

Advert from Choice British Ferns: Their Varieties and Culture by Charles T Druery F.L.S.(late 19th. century).

Commercial nurseries like W. andJ Birkenhead made a good living out of selling ferns, club-mosses and selaginellas to those who couldn't get out into the countryside to dig them up. The fern craze generated a wealth of popular and scientific literature on these plants, with books like .....

British Ferns and their Allies: comprising the Ferns, Club-mosses, Pepperworts and Horsetails by Thomas Moore F.L.S., F.H.S. (1881)

...... Thomas Moore's British Ferns and their Allies, which described them and told readers where to find them, as well as providing detailed advice on how to grow and propagate them. 

Remarkably, pteridomania wasn't confined to adults; there were fern books for children, like Francis Heath's Fairy Plants: a Fern Book for Children. In his preface he wrote "There is probably no part of the beautiful realm of Botany capable of offering so much fascination for young people as that which is dominated, so to speak, by ferns; and it is because I can conceive of no branch of a delightful subject so likely to incalcate ideas of gracefulness and to instil elevating, indeed ennobling, thoughts, that I have written a fern book for children".

Decorated initial letter from Fairy Plants: a Fern Book for Children by Francis Heath

I suspect that the thoughts of most 21st. century 12 year-olds, unwrapping such a book given as a present, would be far from ennobling. 

So why did ferns become so popular?

Illustration from Ferns and Fern Culture by J. Birkenhead F.R.H.S. (1897)

One reason was they did well as house plants in shady Victorian drawing rooms dimly lit my gas lamps, especially if they were grown in the humid confines of Wardian cases, like the ornate examples above.

Illustration from Ferns and Fern Culture by J. Birkenhead F.R.H.S. (1897)

Perhaps the ultimate expression of Pteridomaniacal one-upmanship was to construct a shady, rocky fernery in your garden.

Illustration from the Fern World by Francis George Heath (1879)

This, perhaps, was the ideal - a reconstruction of that shady woodland stream where you originally stole your plants from. The picture caption gives some idea of the effect they were hoping to achieve: 'We look with wonder upon a fairy, dreamy scene of clustering ferny forms in fascinating association with mossy rocks an flowing water'.

Another reason was that the elaborate fractal geometry of fern fronds appealed to Victorian arts and craft taste, in jewellery such as this brooch, and in ....

.... garden furniture. The flatness of a fern frond lent itself to recreation in cast iron or in applied patterns on decorative objects.

The fern craze died out in 1914, but not before it had produced one more fascinating botanical obsession, with monstrosities.

Illustration from Ferns of Great Britain and their Allies the Club-mosses, Pepperworts and Horsetails by Anne Pratt (1855)

This is the typical 'wild type' hart's tongue fern Phyllitis scolopendrium.....

Illustration from Choice British Ferns: Their Varieties and Culture by Charles T Druery F.L.S.(late 19th. century).

....... and these are some of the multitude on hart's tongue mutants that Victorian fern-fanciers raised and which many prized as the gems in their collections. Similarly, .....

...... this is the wild type polypody Polypodium vulgare ....

Illustration from Choice British Ferns: Their Varieties and Culture by Charles T Druery F.L.S.(late 19th. century).

...... and these are some of the many mutants of the same species that were cultivated, most unrecognisable as polypody.

Although Gregor Mendel published his experiments in 1865 his discoveries on inheritance remained unrecognised until 1900, so the Victorians knew nothing about the genetic mechanisms that generated such mutants.It would be more than a century before the science of plant developmental genetics would reveal the ways in which simple gene mutations can generate such spectacular variations in leaf developmental pathways.

Wednesday, January 8, 2014

Insects in mid-winter

Still pretty mild for January - mild enough for these insects to be active:


An unidentified fly feeding on winter flowering sweet box (Sarcococca confusa) this afternoon, carrying a lot of pollen on its hairy body. The books say that sweet box is highly scented - but not to me, I can't smell it. Maybe it's similar to the ability to smell Freesias - some can, some can't. Sweet box certainly attracts flies, though.


Owl midges, about 3mm. long, on the surface of rainwater in a bucket in the garden. They are breeding in vast numbers in the compost bin during this mild weather - every time I open the lid swarms fly out and are fatally attracted to the water. For more on owl midges click here and here and here .


A booklouse (psocid), less than 2mm. long, living in a bag of walnuts (imported from France) that we stored in our conservatory. For more about this unusual but very common little insect click here 

Wednesday, January 1, 2014

Gifts from the sea

Thursday's Guardian Country Diary describes sea glass collecting at Blast Beach, at Dawdon near Seaham on the Durham coast. 

Until about 20 years ago this beach was used for dumping colliery waste and was such a desolate, polluted place that it was chosen as a location for the opening scenes of the 1992 movie Alien 3. Over the last 15 years this stretch of coastline has undergone a major restoration and improves every year - you can find some photos of the wildlife of Blast beach and the nearby Hawthorn Hive by clicking here and here and here.

It was coal dumping that despoiled this coastline but for over 70 years another kind of industrial waste - glass - was thrown into the sea here. That stopped in 1921 but the glass, now sand-polished into pebbles that are used by local craft jewellers, are still washed ashore with every tide. Some of it even ends up on the other side of the Atlantic.

The bottle works at Seaham was opened by John Candlish in 1853, exploiting the convenient supply of local coal from the Dawdon pit, under the patronage of the 4th. Marquess of Londonderry who whose father built Seaham harbour for coal exporting. 

During its peak period of production the Londonderry Bottle Works employed 500 people, producing 20,000 hand-blown bottles a day and burning 21,000 tonnes of coal every year in two twelve-hour shifts that lit up the night sky with the glow from the furnaces. Every week a cargo of bottles was shipped from Seaham harbour to Rotherhithe in the 'bottleboat'. Waste glass was simply thrown into the sea. 

You can read more about the Londonderry Bottle Works by clicking here.

These polished glass pebbles, mostly in shades of green, blue and amber are still washed ashore 92 years after the bottle works closed.