War of the Worlds

Harvestmen are animals that could have stepped straight out of a science fiction story. That globular body, slung between unfeasibly long angular legs, could easily be a Martian fighting machine, striding through hordes of fleeing, terrorised refugees in War of the Worlds....... or maybe I’ve got an overactive imagination..... but check out the CD cover for Jeff Wayne’s musical version of War of the Worlds (see http://www.coverbrowser.com/image/bestselling-music-2007/3826-1.jpg) and I think you’ll see what I mean.

You do need a pretty vivid imagination to come close to understanding how these strange animals perceive their surroundings. Those two eyes, on either side of the turret on top of their body, are not particularly effective and they mostly explore their surroundings using their senses of taste and smell, which are located on their palps, on either side of their mouth (just visible behind the front leg in the picture above - double-click on the image for a larger view)), and on their second pair of legs. Notice how, in the pictures above and below, this harvestman is lifting and extending one of its second pair of legs towards the camera – it’s smelling me. They take great care of that vital second pair of legs and if you watch one of these animals for long enough you’ll notice that it will draw each of this pair of legs through its jaws quite frequently, to keep these sensory limbs clean and in tip-top condition.

There are scores of these intriguing animals in our garden at the moment, striding through the dry grass and dead leaves in that cautious, fastidious way in which they move, searching for small insects to feed on amongst the decaying vegetation of autumn.

 

Deadlock

A while back I described an encounter between a wasp and a large yellow underwing moth (see http://cabinetofcuriosities-greenfingers.blogspot.com/2009/07/unlucky-moth.html) where there was only ever going to be one outcome, but today I watched a wasp grapple with a more formidable opponent where the winner was always in doubt. The wasp blundered into a spider’s web spun in an umbel of hogweed and after a frantic struggle managed to free itself, but not before the spider had leapt onto the wasp. They hung together in the wrecked web for a few seconds, while I took these pictures.

Each grasped the other by its opponent’s jaws, while the wasp couldn’t quite bend its abdomen down far enough to sting the spider. Deadlock. Then the wasp broke free and flew off with the spider still attached, so I’ll never know the outcome of the contest. Maybe, during its initial lunge, the spider managed to inject enough venom to kill the wasp and they both plunged to the ground, where the spider finished the job. Maybe the wasp stung the spider and settled to dismember its attacker. Which would you put money on? Anyone know what spider this is?

Naked Ladies

Yes, that is a cheap, attention-seeking headline; botanically, 'naked ladies' is nothing more than a slightly salacious name for autumn crocus aka meadow saffron aka Colchicum autumnale. This plant's ‘nakedness’ stems from its lack of leaves, which aren’t produced until spring – the beautiful lilac flowers, very attractive to bees, appear without any accompanying foliage in grassy places in early autumn. This is a rare wild plant and most specimens that turn up – like these beside a road in Weardale – are probably garden escapes. In the wild the plant was ruthlessly eliminated because it’s extremely poisonous to grazing livestock, thanks to the presence of toxic colchicine in all parts of the plant. Like many plant poisons colchicine has been used medicinally, in very low doses, to treat gout. It’s also used by crop breeders to double the number of chromosomes in plants, because the drug allows cell nuclei to divide without the cell they are in dividing, so doubling the number of chromosomes in the cell - a phenomenon known as tetraploidy. More chromosomes per cell tend to produce larger cells and larger cells lead to larger plants and better crops. All sorts of unnaturally large plants, ranging from some strawberry varieties strawberries to hyacinths, have been bred using this long-standing form of genetic manipulation, which has been in use for over a century. Crossing a tetraploid with a plant with a normal complement of chromosomes produces plants called triploids, with three sets of chromosomes per cell, which are seed- sterile – a common breeding technique for producing seedless fruit.

Magic of the Hemispheres

Remember those rotating globes of the world that used to be in every school classroom? I recall having a miniature version given to me as a Christmas present by parents who probably hoped it would sharpen up my performance in geography classes. The globe separated around its equator into two hemispheres, just like this scarlet pimpernel Anagallis arvensis seed capsule, which separates and releases a shower of seeds from within it you gently squeeze it. For the plant in flower, see http://cabinetofcuriosities-greenfingers.blogspot.com/search/label/Anagallis%20arvensis)

Botanically, this form of capsule is called a pyxidium - useful to remember if you've got an x to get rid of in a game of scrabble. Plantains (Plantago spp.) have a similar arrangement in their rows of minute capsules, although they're smaller and less aesthetically pleasing.

The Plant that Ate a House

Well, not quite............but this is what happens when you plant Boston Ivy (Pathenocissus tricuspidata) and forget to prune it. This house, in the centre of Allendale in Northumberland (see http://www.northumberland-cam.com/allendale/), makes a stunning impact when its cloak of foliage changes colour in early autumn. This rampant climber scales walls using sticky pads on the tips of tendrils, which glue it to the wall surface.  Recent research in China suggests that this adhasive ability and rapid growth might make this a useful plant for stabilising unstable rock surfaces, like the faces of abandoned quarries.

The name Boston ivy relates to its use to cover buildings in that state, not to its geographical origin which is eastern Asia.

Flower Animal

Sea anemones belong to a class of animals known to science as the Anthozoa – a word that literally means ‘flower animal’, and these beadlet anemones (Actinia equina), photographed on the beach at Warkworth in Northumberland, are typically flower-like. There’s some debate about whether the green individuals like the one in the photo below are just a colour form or a separate species. On the upper shore the purple form is by far the commonest.

The ring of tentacles encircling the mouth are equipped with barbed stinging cells called nematocysts, triggered when prey brushes against them, that inject paralysing poison into their victim, which is then manoeuvred through the mouth and into the stomach by the tentacles. The nematocysts of British sea anemones are too small to penetrate human flesh but you can feel the barbs. Poke you finger into a beadlet anemone and it feels sticky – the 'stickiness' is due to the microscopic barbs hooking onto your skin. Incidentally, these pictures were taken with the little Pentax W20 pocket camera, that I use for most of the pictures on this blog, fully submerged in the rockpool; so far the manufacturer’s claim that it’s waterproof has proved to be sound. It’s ideal for taking pictures of animals in rockpools, avoiding the problems of reflections that are inevitable when photographing through the surface.

One of the finest books on sea anemone’s was Philip Henry Gosse’s Actinologia Britannica; A History of the British Sea-Anemones and Corals, published in 1860 and illustrated with beautiful hand-coloured plates showing all the then-known British species. A copy of this would now cost you somewhere between £250 and £600, depending on condition, but you can read the book for nothing on the web (or even download a pdf of the whole book) at http://www.archive.org/details/actinologiabrita00goss
For some more up-to-date information on beadlet anemone, take a look at http://www.marlin.ac.uk/speciesinformation.php?speciesID=2359

A Study in Scarlet.....

....and crimson.

Why are so many berries – including the species below - red?

Guelder rose

Hawthorn

Sorbus (intermedia?)

Bittersweet

The standard answer is that bird vision is particularly sensitive at the red end of the spectrum, which is why they’re attracted to red fruits. Bird pollinated flowers in the tropics tend to be red too. It’s undoubtedly true that there is a correlation between this colour and attractiveness to birds, but it’s also now known that birds are also able to see ultraviolet, at the opposite end of the spectrum – a wavelength that our eyes are not sensitive to. So we can’t make an absolute direct comparison between the colours that we see and the colours that birds see – when we see purple, for example, it’s a combination of blue and red light reflected from opposite ends of our spectrum of visual perception. Bird purple would be a combination of ultraviolet and red – whatever that might look like. Although we can’t have absolute knowledge of the colours in bird-world, what researchers can do is to present birds with colour choices to see what they prefer...... and that produces some interesting results. It turns out that it’s not just the colour of the berries in our visual spectrum that's important - it's also the contrast between the colour of the berries and the background, including UV light reflected or absorbed by leaf sufaces, that’s also important – the contrast between berries and the background affects the choices that birds make, not just the colour of the berries. Also the waxy  ‘bloom’ on many black, blue and purple fruits (like bilberries) reflects UV light, which makes them conspicuous to birds – rub the bloom off and birds tend to be less attracted to them. Finally, experience counts too - juvenile and adult redwings show different preferences, so learning has a role in associating fruit colour with the best food sources. As in so many branches of science, research hasn't yielded clear-cut answers yet, but it has produced some very interesting questions. The story has as many twists and turns as a Shirlock Holmes mystery. What is certain is that simply trying to interpret what birds (or any other animals) see according to what we see is unlikely to give a true impression of the way the world looks to them.

Spot the Shrimp.... and Mind where you Tread!

At this time of year the pools of water left on sandy beaches at low tide are full of shrimps, although you need to look very carefully to spot them. This one, given away only by its white legs, was hidden in a pool on the beach at Warkworth in Northumberland last weekend. Double click on the picture for a larger image and you can just make out its tail, on the left, and the pair of stalked eyes (with a white mark between them) that protrude above the sand when it buries itself. The speckled pattern on the exoskeleton of the animal provides almost perfect camouflage

In this enlarged image, above,  you can see the eyes and legs a little more clearly....

Anyone going shrimping on a sandy shore would be wise to wear shoes when they wade in the shallows at this time of year because venomous weever fish feed on shrimps and when the water warms up they come inshore to catch them. This one was partially buried in the sand on Warkworth beach.

The three spines on the dorsal fin, seen erected in this disgruntled lesser weever Echiichthys vipera , are tipped with venom that causes excruciating pain for anyone who treads on one with bare feet. A trip to the beach then ends with a trip to the local A&E hospital. I rescued this fish from a gaggle of gulls that were attacking it in the shallows but were still very wary of it.

Despite their evil reputation for inflicting pain, weever fish have the most beautiful emerald eyes, set in a gold circlet. Usually the fish would be more deeply buried in the shallows, with just eyes and spines above the sand.

You can read more about weever fish at http://www.marlin.ac.uk/speciesinformation.php?speciesID=3221

Sea Gooseberries

Sea gooseberries, rescued from the beach at Warkworth

Each animal is as transparent as glass, although the tentacles carry a hint of purple

Eight rows of beating hairs, arranged like combs, provide the propulsion. The pink blobs are retracted tentacles

A sea gooseberry swimming left to right and extending one of those lethal tentacles.

A tentacle fully extended, danging below the animal to catch prey,

which is then reeled in

A swimming sea gooseberry, propelled by the rows of 'combs' (which is why these are sometimes called comb jellies), and training tentacles

The rows of cilia make these very manoeuvrable animals -

this one of spinning on the spot, trailing tentacles

Every wave that lapped onto the sandy beach at Warkworth on the Northumberland coast this afternoon washed up scores of blobs of glistening jelly, each about the size of a currant – about 5mm. in diameter. When I scooped some up into a plastic pot and added sea water they turned out to be sea gooseberries, otherwise known as comb jellies. These tiny predatory animals drift in the plankton, suspended by eight rows of constantly beating hairs arranged like combs (called ctenes) and dangle a pair of long tentacles that catch small prey items and draw them up into the animal’s mouth. They are exquisite little organisms, as transparent as glass and flashing with electric blue and green iridescent colours generated by their beating hairs when they catch the sunlight. There must have been tens of thousands of them drift in the plankton just offshore this afternoon. I managed to get some home alive and took some pictures under the microscope, which you can view over at http://beyondthehumaneye.blogspot.com/2009/09/sea-gooseberries.html and I've posted some videos at http://beyondthehumaneye.blogspot.com/2009/09/sea-gooseberry-videos.html

A Poke in the Eye from a Teasel

The teasels Dipsacus fullonum in my garden are beginning to shed ripe seeds, so I’m expecting the local goldfinches to show up any day now. This species’ liking for teasel seeds is legendary and I read recently that it’s only the males, which have more slender beaks than females, that can reach the seeds (see http://www.arkive.org/goldfinch/carduelis-carduelis/info.html). Can this really be true? If so, why does this sexual difference in goldfinch beak shape exist? The forest of spines on the teasel seed heads is surely a defence mechanism that has evolved to keep hungry birds at bay, by poking them in the eye, so it might be expected that natural selection, which operates to preserve features that enhance the fitness (reproductive potential) of a species would ultimately favour the evolution of teasel heads with longer spines, which would force even the slender-billed male goldfinches to keep their distance. Interestingly, plant breeders at the International Centre for Research in the Semi-Arid Tropics in India have been breeding pearl millet varieties with extra-long bristles in their seed heads for just this purpose – for keeping flocks of finches at bay by irritating their eyes and beaks when they try to eat the grain (see http://www.new-ag.info/98-1/focuson.html)

Exploding Acorns

Knopper galls (above), uninfected normal acorn below 

These weird objects are knopper galls, caused by a tiny wasp called Andricus quercuscalicis, that I found on oaks growing beside the River Tyne at Wylam this morning. The wasp lays its eggs in flower buds which, instead of developing into acorns, grow into these popcorn-like galls that provide a home for the wasp larvae and pupae through the winter. The young galls are bright green and covered in sticky sap, but as they age they turn brown before dropping off. If you collect a few and keep then in a dry container over winter you can watch the minute wasps emerge through the pore in the gall in spring. The causative gall wasp first arrived in Devon sometime in the early 1960s, having slowly spread across Europe from Turkey, and colonised rapidly once it arrived in England, so it’s now well established throughout most of Britain and well into Scotland. It first arrived here in the North East in the 1980s. The conspicuous damage that it does to acorns led to widespread speculation that it would destroy the acorn crop and would be a major threat to the future of oaks in Britain, but infestation levels vary a lot from year to year and it’s unlikely that this minute wasp poses a long-term threat to our national tree. Whenever you see a knopper gall (usually on pedunculate oak Quercus robur), there’s sure to be a Turkey oak Quercus cerris (identifiable by its hairy acorn cups) somewhere nearby, because the wasp spends half of its life cycle on this introduced tree, which is widely grown in parks, arboreta and large gardens, and the remainder on native pedunculate oak.

Turkey oak acorns

Rats!

There is a saying – widely regarded as an urban myth – that ‘in a city you are never more than ten feet from a rat’. Well, myth or not, in Newcastle this afternoon we were within less than ten feet of about twenty rats that were scampering over a triangle of grass near a pub, feeding on the lunchtime debris left in the grass around the picnic benches. The brown rat Rattus norvegicus is arguably second only to Homo sapiens as the world’s most successful urban mammal. We sat and watched them scampering around for about ten minutes, but unfortunately I only had a small pocket camera with me, so the pictures are not very good, but at least you can get some idea of the company we’ve been keeping today! While we were watching, as well as eating food scraps the rats were also eating grass and grass seeds, but never once attempted to nibble the scores of cigarette ends strewn around the benches – not a single smoker amongst any of them. Mostly they didn't take much notice of our presence, although they scampered back under the laurel hedge if we made any sudden movements.

Antopolis

Hamsterley Forest http://www.forestry.gov.uk/hamsterleyforest, which lies between Weardale and Teesdale, is home to an enormous variety of fascinating wildlife, ranging from nightjars and crossbills to adders, badgers and deer, but these wood ants are amongst the most amazing and perhaps the most numerous of all the animals in the forest. The bottom photo shows a nest, built of pine needles and often half a metre high. Each nest is reckoned to be home to around half a million ants. The ants’ nests are rather like icebergs, with most of the galleries and chambers hidden below the surface, and in some places there are several nests linked together underground, forming an ant metropolis. The top of the nest seethes with ants, constantly setting out in long columns on foraging expeditions that take them right to the top of tall conifers in search of small insects that they bring back to the brood. Understandably, the presence of these ants is welcomed by the foresters because this free pest-control workforce destroys a significant proportion of the pests that infest conifers, although the ants farm the aphids rather than killing them, collecting the sugary honeydew that the aphids excrete. It’s best not to hang around for too long when you’re photographing these nests, as the occupants quickly find a way up your trouser leg and have a very painful bite. You can read more about wood ants (and access photos and videos) at the following web siteshttp://www.treesforlife.org.uk/tfl.woodants.html
http://www.arkive.org/scottish-wood-ant/formica-aquilonia/
http://www.arkive.org/hairy-wood-ant/formica-lugubris/
http://www.arkive.org/southern-wood-ant/formica-rufa/

Carnivorous Ink Cap

Shaggy ink caps Coprinus comatus seem to be particularly abundant on disturbed habitats like road verges. Their season is quite short, peaking in September and early October and although they are edible you need to be quick if you want to harvest edible specimens. The life of each toadstool is very short, erupting through the grass on one day and almost immediately beginning to dissolve into an inky mass of spores that are dispersed by flies. This fungus is not just unusal in using insects to disperse its spores – it can also feed on animal tissue. Some research carried out in recent years in China has confirmed that this is one of several fungi (another being the oyster mushroom Pleurotus ostreatus) whose hyphal exudates can stupefy and kill nematode worms in the soil, which they then digest with their invasive hyphal threads. Shaggy ink cap is a carnivore - which raises some interesting questions about whether you should eat it if you are a strict vegetarian! In evolutionary terms fungi are much more closley related to animals than plants anyway. You can read about research into shaggy ink cap's nematode-eating activity at http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1932715

For more on this fungus and many others, also take a look at Tom Volk’s outstanding web site at http://tomvolkfungi.net/