Wednesday, December 26, 2007

A Nematode Worm

I am an amateur naturalist trying to learn a little about everything living in my garden.

When I started my blog a year ago, in order that I might avoid "species-count overload" (something that raised some comment and debate at the time) I made the rule that I'd confine my attentions to creatures of a 'sensible size' (a few mm upwards). This remains my broad intention. Since, however, a) rules are made to be broken, and b) Santa has recently been kind enough to deliver me a copy of Life In The Soil (James Nardi, The University of Chicago Press) which contains instructions for making a soil-sampling device known as the Baermann funnel, I can't resist devoting a posting to one of the smaller denizens of my garden.

So, what is a Baermann funnel? As the book says, it is a device whose extreme simplicity belies it's enormous effectiveness in extracting creatures from soil samples. My version is shown in photo 1. To make one, simply cut the end off a plastic fizzy-drinks bottle, fill with an inch of water, stuff a handful of soil inside a muslim bag or stocking (anything with holes small enough to retain the soil but allow small critters to wriggle through), place inside the section of bottle and then stand, cap down, inside a pot so as to position the the lower part of the soil in darkness. Finally stand the whole thing under a source of light (e.g. a desk lamp). Critters in the soil, eager to escape the bright light and heat from the lamp will wriggle down through the soil, through the holes in the stocking and out into the water. After a couple of hours you can unscrew the bottle cap, let the water out into a saucer and look to see who's now swimming around in it....

...and unless you happen to have taken a soil sample from Mars or somesuch, the answer will be: Nematode Worms.

Why? Because, quite simply, nematodes are the most numerous (multicelled) animal on the earth. A square metre of soil may contain a million of them. They are found everywhere (p176 onwards of this book) from the rainforests, to Antarctica, to the mud in the bottom of the ocean, to the soil in my vegetable patch. The much cited quote is from Nathan Cobb, "the father of nematology in the U.S.", who gave the following powerful description of their ubiquity:

"[...] if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we should find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of the various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species could be determined by an examination of their erstwhile nematode parasites."

Togther with some nice animations pertaining to the body parts of nematodes, The Virtual Nematode site even has a computer-generated movie of the nematode-remains of an earth-blown-apart!

So, what did I find in my Baermann funnel. Answer, within an hour I'd collected more than twenty worms from a single handful of soil. Photo 2 shows one of them (40x magnification, click on photo to enlarge).

Now, those of you who follow my postings will know I generally make some effort to try to establish the specific species of creature I've come across. In the case of my nematode however, I feel I may have met my match. According to the book above some 15,000 species of nematode are known. If this weren't daunting enough however, it's estimated this may represent only about 3% (!) of the number of species awaiting discovering. It's probable that new species are appearing, and sadly that human activity is extinguishing others, all the time. If you want your name associated with the discovery of a new species of animal, you could do worse than to make a Baermann funnel!

I've not tried to work out the species of my nematode. It could be that I am making too much of the difficulty of identifying nematodes however (?). Certainly the UNL Nematology Lab has an online interactive key which looks a good way to get started. It seems you can make some headway by looking to see whether the mouthparts of your worm are those of a herbivore suited to piercing plant roots, those of a bacterivore suited to hoovering-up bacteria, or 'other' (fungivore, fellow nematode predator etc.). If you're an amateur brave enough to be cataloguing the nematode fauna of your back yard do please leave a comment.

Monday, December 24, 2007

European Holly Ilex aquifolium

I am an amateur naturalist trying to discover a little about everything living in my garden.

Today's posting is something of a milestone for me as it marks not only my 'species count' reaching fifty, but also one year (give or take a few weeks) since I started blogging the life in my garden. Looking through my window, I find my perception of my garden has been entirely transformed over the course of past year. Previously my garden was a place where 'some plants and stuff grew'. When I look at it now, it seems to be positively vibrating with life; I now know it's a place where snails stab each other with daggers in the name of love; native plants rub shoulders with exotic immigrants; spiderlings enagage in matricide; earwig mothers lovingly tend their eggs; female moles fight aggressive underground battles; ants ferry primrose seeds to and fro; fungal threads push their way through the soil and little lichens eek out quiet lives on exposed stone ledges. To name but a little of the activity going on all around me.

In the year since I started my blog I've had 2859 visits from 851 cities acround the world. At least a few of you have come back more than once, so I guess my postings must provide some small entertainment value. The purpose of my writing has always been to help fix in my own mind a little of the natural history of my garden. If in the process, I'm able to provide a few minutes diversion for some of you out there, I'm very happy.

Enough of the self-referential ramblings! On to the star of today's show, and what could be more appropriate to this festive season than photo 1 (click to enlarge), European Holly (Ilex aquifolium).

According to my copy of The Collins Tree Guide (Johnson and More), the holly (Ilex) genus contains some 400 species (together with numerous garden-centre cultivars). Only one is native to Europe, though as the book says, European Holly (Ilex aquifolium) 'has some claim to be the most ornamental of all' - a sentiment with which I'm in full agreement.

In common with nettles, Holly is mostly dioecious (Greek 'two houses') meaning that individual plants are either male or female and cross-pollination is required to produce a 'berry'. Male flowers can be identified by the presence of four, yellow anthers. Females have a single style.

Holly berries are toxic. According to this site as few as three berries are sufficient to bring on unpleasant side effects.

Strictly, as pointed out in my copy of The Field Guide to Trees (Mitchell, Collins) holly berries are not in fact berries at all. Instead, they are what botanists term drupes. As this site explains, berries have seeds directly surrounded by soft fleshy fruit (grape pips being an example), whilst drupes have their seeds surrounded by a woody 'shell' ('endocarp') (as peaches do).

Holly is a popular food with the caterpillars of the Holly Blue butterfly (Celastrina argiolus), the Double-Striped Pug moth (Gymnoscelis rufifasciata) and the Holly leaf miner (the larvae of a fly, Phytomyza Ilicis). According to a paper by T.R.E. Southwood from 1961 however, of all the common species of British tree, holly has the lowest number of predatory insects - a mere seven species. I find this amazing. There are simply so many (tens of thousands at least) of insect species in Britain, and they are so good at finding ways to eat things, that for one of our commonest woodland trees to be 'immune' to the advances of all but seven really surprises me. Unfortunately reading the full paper above would require me to pay a subscription (see here for my grumble about this) so I've not been able to learn more about the details (if anyone can give me a simple explanation of why so few insects predate holly, do please leave a comment).

Photo 2 shows a close up of the trunk of my holly tree (which is growing at (1.6,1.7) - see here). Holly wood is pale and has been traditionally used to make the white pieces in chess sets. On the odd occasion when I've found the need to prune my tree I've found the branches to be tough and flexible. Pure speculation on my part, but I can imagine hunter-gatherers in Britain a couple of thousand years ago finding a use for the strong bendable branches of holly as lashings.

A more certain past use of holly wood has been for the manufacture of bird lime (a sticky glue used to coat twigs for the purpose of catching song birds alive). I haven't come across a definitive recipe (not that I'd want to make said glue in any case!) but I understand it involves boiling and fermenting the wood and bark in water.

As most people know, holly has a strong symbolism in Christianity, the spiky leaves being associated with Christ's crown of thorns, and the red berries with drops of His blood, hence the line from the famous Christmas carol The Holly and The Ivy

Of all the trees that are in the wood
the holly bears the crown

I read that the religious symbolism of holly stretches much further back into the past, to pre-Christian times. I find so many supposed 'factual' accounts of pagan rituals, Druids etc. on the web to be such a mix of fable and wishful thinking however, that I struggle to know which to believe. I'll defer further comment therefore (if anyone can point me to an historical account from some reputable source do please leave a comment). Instead, I'll leave a final, upbeat word to who else but Willie Shakespeare:

Then heigh ho! the holly!
This life in most jolly!

Happy Christmas all!

Saturday, December 22, 2007

Intermediate screw moss Syntrichia (syn. Tortula) intermedia

I am an amateur naturalist trying to learn something about everything living in my garden.

Photo 1 (click to enlarge) shows a patch of moss growing on top of a large stone in my garden, closeby my kitchen door (at (0.9,1.5) - see here).

In fact there are a number of mosses present in photo 1. Though I've not taken the time to examine it in detail, from its appearance I believe the flat feathery one below the coin in the centre of photo 1 to be our old friend Silky Wall Feather moss (Bracythecium rutablum).

The moss that's the focus of today's posting however is that directly left of the coin with leaves arranged in little 'rosettes'.

Photo 2 shows a close up (100x magnification, 1 small graticule division = 10um) of one of the leaves. Things to notice include the tiny spines on the translucent hair emerging from the end of the leaf; the rounded leaf end; the fact that towards the mid-point along its length, the leaf narrows a little and simultaneously 'recurves' (folds over at the edge). Another microscopic feature, most easily seen in the 400x image of photo 3, are the circular cells in the mid leaf, becoming oblong at the edges. Finally, a feature of my moss shown in photo 4 (I've 'tweaked' the colour and contrast on this photo to show things up a little better) are its brown, cylindrical setae (spore capsules). Taken all together, and referring to my battered copy of British Mosses and Liverworts (E.V.Watson, Cambridge Univ. Press 1955), everything points to my moss being Tortula intermedia (Intermediate Wall Screw moss). The site of the British Bryological society has a lovely close-up photo under the alternative name Syntrichia intermedia.

Ubiquitous and persisting through the winter, mosses are inherently 'good value' for the amateur nature lover (a remark I've made previously and heard reiterated on a radio documentary I enjoyed listening to recently via the BBC website). My blog has been my introduction to the mosses and I've thoroughly enjoyed discovering that life forms I'd previously regarded as 'undifferentiated lumps of green stuff' possess, in fact, a minute individuality and beauty all of their own. This is my second Tortula moss but once you've accustomed yourself to notice the difference there's no mistaking the green rosettes of our moss above from the the frosty-white pincushions of Tortula muralis I photographed a year ago. Hooray for the beautiful bryophytes!

Wednesday, December 19, 2007

Two fungi on apples - Venturia inaequalis and a Mucoraceae species.

I am an amateur naturalist trying to discover everything living in my garden.

I have a cooking-apple tree growing in my garden (more on which in a future posting). It produces far more apples than I can cook and winter finds my lawn carpeted with a layer of rotting windfalls. At the time of writing, a flock of songbirds (blackbirds, thrushes, redwings, starlings, fieldfares and others) are visiting my garden daily to eat their fill. Birds are not the only things devouring my apples however...

Photo 1 (click to enlarge) shows an apple clearly afflicted with an outbreak of brown scabs. Recently I acquired a second hand copy of Garden Pests and Diseases (Brooks and Halstead, publ. Simon and Schuster) and from this, and some follow-up searches on the internet, I understand the cause to be a fungus called Venturia inaequalis.

V.inaequalis infects both the leaves and fruit of apple trees and is a member of the enormously numerous division of fungi, the ascomycota = those fungi that "ripen" their spores inside tiny, sausage-shaped tubes called asci (see here for my photo of some asci and here for some more description from me).

In the case of V. inaequalis the spore-containing acsi are, in-turn, packed inside a body known as a psuedoperithecium (a "spore salt-shaker"). I made a little effort myself to try to obtain a microscope photo of one of these, but the strength of my resolve was weakened when I found the matchless images on Tom Volk's website (in any case, I believe I'm unlikely to find a 'fruiting' scab as I've read the pseudoperithecia tend to occur in Spring and are more common on the leaves).

In terms of edibility, brown scabs on apples are entirely harmless (no doubt the same can't be said of the fungicides commerical growers spray on apples to prevent scabs appearing!). Indeed, I've even heard it suggested that amongst the reasons for an increased incidence of cancers in the Western population is our unwillingness to imbibe a healthy population of micro-fungi on our vegetables. I can't vouch for the scientific validity of this theory. I do know you'd need to be very hungry to eat the apple in photo 2!

Looking closely at photo 2 you might notice the small white patches of mould upper left and centre. Viewed under the microscope (approx 40x magnification) a strange and delicately beautiful structure is revealed (photo 3).
On the basis of looks alone (always dangerous when dealing with fungi) and the excellent photo's on this site, I'm identifying this as a member of order the mucoraceae, the 'pin-head' moulds. The 'pin-heads' are technically known as sporangia and are filled with spores. They turn black as the spores mature (as some have in the photo).

To attempt to pin down my mould to one of the three-hundred-or-so mucoraceae species is really the domain of experts. Increasingly DNA analysis is emerging as the only sure-fire method for the identification for micro- (and indeed some macro-) fungi. Taking a shot-in-the-dark however I'll go with Rhizopus stolonifer and invite the experts out there to correct me.

V.ineaqualis and and R.stolonifer are far from the only fungi to attack apples (see here), I'm quite sure more searching would turn up more (a project for a future posting perhaps). For now I'm happy to chalk-up two more species on my garden checklist.

Finally, I mentioned the birds above feeding on the apples on my lawn. Watching them it seems they actively seek out the more rotten apples. I wonder whether they get some health benefit from this (the consumption of pencillin moulds perhaps?), or is it simply that the mouldy ones are the softest and best-tasting. A case of Stilton cheese at Christmas!

Monday, December 17, 2007

Red Underwing Moth Catocala nupta

I am an amateur naturalist trying to find out what lives in my garden.

Photo 1 (click to enlarge) shows a large moth that I found powerfully fluttering its way around my garden one afternoon, late last summer. From R. Lewington's truly beautiful illustrations in my newly acquired copy of the Concise Guide to Moths of Great Britain and Ireland (Townsend, Waring, British Wildlife Publishing ) I'm confident to identify he (or she - can anyone comment?) as a Red Underwing (Catocala nupta).

The book lists eight species of Catocala moth, a number of which (the Red, French Red, Rosy, Light Crimson and Dark Crimson Underwing) are superficially rather similar.

The caterpillars of the Red Underwing feed on willow and poplar.

In Greek 'kato' means 'below' and 'kalos' 'beautiful' (see here for a detailed discussion) - hence Catocala - a genus of moths with 'beautiful hind wings'.

The species name nupta means 'a bride' and was coined by the father of modern taxonomy Carl Linnaeus. Linnaeus was apparently fond of giving this name to moths with bright underwings and in my copy of the fascinating Moths (Michael Majerus, New Naturalist series) A.M. Emmet is quoted as wondering whether brides in eighteenth-century Sweden were in the habit of wearing brightly coloured underwear!

The red underwings serve as a defense against predators. In his book Michael Majerus suggests two mechanisms: firstly, the flash of red and black from the underwings may serve to remind birds of unpleasant tasting insects such as wasps or ladybirds. Secondly, a predator with its mind focused on chasing a flying moth "with red wings" may lose track of its prey when the moth lands, closes its wings (photo 2), and instantly becomes a dull cryptic grey/brown well camouflaged against a tree branch.

Another interesting fact I discover from the book above is that Catocala nupta has been recorded as showing full industrial melanic polymorphism - or, in layman's terms, the advent of heavy industrialisation has caused the evolution of a subspecies of Red Underwing with darker wings designed to give the moth better camouflage against grimy, polluted surfaces (soot-stained tree trunks etc.). Strictly, I'm taking some licence in my explanation: in point-of-fact the book merely states that a melanic form of C. nupta exists without giving any details of its camouflage strategy. (The famous example of a melanic moth is the Peppared moth which has provided a vehicle for extensive studies of Darwin's theory of evolution - Majerus' devotes a an entire chapter to a fascinating account of these studies). I've searched the internet in vain for an image of a melanic Red Underwing (anyone?), although Townsend and Waring's book does contain a picture of a form ("f.") of the Red Underwing Catocala nupta f. brunnescens, which has dirty brown underwings. Can anyone tell me whether this is one-and-the-same as a melanic C.nupta?

Sunday, December 16, 2007

Orb web Spider Tetragnatha extensa

I am an amateur U.K. naturalist trying to discover all the things living in my garden.

Further to the wealth of excitement my first spider posting provoked amongst my legions of readers (hem,hem), photo 1 (click to enlarge) shows another spider I found hanging in the centre of his web in an overgrown corner of my back garden (at (0,2) - see here).

You'll note I refer to my spider as a 'he': Using a hand lens I was able to confirm the presence of palps ending in swollen bulbs.

Back in late-April, when the photo was taken, working with my copy of Spiders (Michael Roberts, Collins Field Guide) I felt I came to a reasonably confident identification of my spider as Tetragnatha extensa. Looking now at my modest-resolution photo, I don't claim to unreservedly stand by this (T. montata might be a alternative (?) for example), but in the absence of better evidence it'll have to stand.

Eight species of the Tetragnatha spider genus are found in Northern Europe. All spin orb webs. Shortly after completeing the web, they take a few seconds to bite a hole out at the centre, there to take up residence waiting for lunch to arrive.

Gnath in biology refers to the jaws, hence Tetra'gnatha "four jaws", a reference to the fieresome mouthparts of these spiders. Photo 2 is my (untrained amateur's) attempt to sketch what would very likely be your terminal sight were you unfortunate enough to find yourself a small fly trapped in an extensa's orb web! The long 'mouthparts' on which the fangs are hinged are known as chelicerae. The chelicerae are used in mating, with the male and female locking theirs together. Atop the chelicerae sits the spider's turret-shaped head with its eight eyes.

T. extensa is one of the commonest Tetragnatha species in Britain and apparently tends to favour a residence close to open water (a slight puzzle in this case since, aside from an open water-butt, that corner of my garden doesn't have any). My copy of The Biology of Spiders (Foelix Rainer, Oxford Uni. Press) refers to a Tetragnatha spider being able to walk on water at 15-20cm/sec (the book doesn't state the species, but from the description I take it to be extensa).

Finally, in case you're wondering about the curious black cylindrical object on the left of photo 1: This is a handy design I got from Dr. Robert's book above for an insect (/spider) viewer. Very simply it comprises two concentric cylinders (in this case the plastic lids from two antiperspirant sprays). The larger has a hole cut in the top. The idea is to pop the insect between the two, and cover the hole with cling-film ('plastic wrap' to those of you reading in the US). By sliding the smaller tube up like a plunger, the insect becomes trapped, immobile against the film and hence easy to examine with a hand lens. Provided you don't keep it there too long, the critter need suffer no ill effects and can be set free afterwards. Neat heh!

Saturday, December 15, 2007

Yellow Corydalis Pseudofumaria (corydalis) lutea

I am an amateur naturalist trying to discover everything living in my garden.

Growing wild under the hedge at rear of my garden (at (0.8,2.0) - see here) are a number of patches of the yellow-flowered plant seen in photo 1 (taken back in early summer) . Photo 2 (click on photo's to enlarge) shows a close up of the pretty, trumpet-shaped flowers.

A short time spent with my copy of the excellent Wildflower Key (Francis Rose, Warne 2006) and I'm confident in identifying my plant as Yellow Corydalis (Psudeofumaria (Corydalis) lutea).

From the book above I learn that the plant family the Fumariaceae (the Fumitories) are related to the poppies (see here). The book lists eleven British species. From Wikipedia's entry however, it seems there is some debate amongst botanists as to whether the the Fumariaceae truely constitute a plant family.

The book describes Yellow Corydalis as introduced to Britain from E.Europe, though "possibly native in Kent". I can say that having learnt to recognise it, I've found it to be quite common, growing wild in Oxfordshire.

Confusingly, the official Latin name for Yellow Corydalis has changed from Corydalis to Pseudofumaria, to reflect that fact that the members of the former plant genus have simple stems whilst the latter have branched stems.

Turning to the internet I can find almost no information specific to my Yellow Fumitory (if anyone can point me to some do please leave a comment). I have come across a range of descriptions of its cousin pink-flowered cousin, Common Fumitory (Fumaria officinalis) however. Common Fumitory is distinguished by having a single seeded fruit (achene) whilst the other fumitories (including Yellow Corydalis) all produce capsules containing multiple seeds.

My copy of The Englishman's Flora (Geoffrey Grigson, Paladin) has no entry on Yellow Corydalis, but once again does discuss Common Fumitory. It seems there is some debate as to whether the name 'fumitory' refers to the pungent, eye-watering smoke that the plant supposedly emits when burnt, whether it is a reference to the 'smokey' colour of the foliage or whether it is a reference to the 'nitric-acid-fumes' smell of the roots. Referring to the second possibility, Grigson quotes William Coles' description of the foliage in his book Adam in Eden (1657) as

"a whitish blew colour as smoak is"

He also gives a rather nice quote from a Stockholm medical manuscript (c.1400)

"Fumiter is erbe, I say,
That springyth in April and in May
In feld, in town, in yerd and gate
There land is fat and good in state"

The poetry prize has to go to Jon Clare who (as I discovered from this site) writes:

"And Fumitory too, a name
Which superstition holds to fame,
Whose red and purple mottled flowers
Are dropped by maids in weeding hours,
To boil in water, milk, and whey,
For washes on a holiday,
To make their beauty fair and sleek,
And scare the tan from summer’s cheek"
(John Clare, quoted by Ann Pratt, ‘Wild Flowers’ (1857)

Can any maids out there report having tried this?!