Sunday, December 27, 2009

High-density Housing (for Bryozoans)

This beautifully geometric piece of natural architecture is produced by the animal commonly called the sea-mat and scientifically known as a bryozoan (which means 'moss-animal'). This particular species is Membranipora membranacea and I picked it up yesterday, in a rock-pool on the seashore at Seaburn, near Sunderland.

Membranipora forms extensive, fast-growing colonies resembling a lacy mat, that spread over the surface of kelp fronds. It's common on all coasts around Britain and has been introduced into shallow seas in other parts of the world where there is some concern that its rapid rate of growth could suppress the reproduction of some marine algae.

Each calcareous compartment, secreted by the animal inside, contains an individual animal (zooid) that extends a feeding arm called a lophophore, for filtering out plankton.

The zooids retract into a tube within their walled enclosure at the slighest hint of danger but when they're all extended they resemble a garden of transparent flowers, gently waving their arms..

Each walled enclosure has a small tower at the junction with its neighbours' walls and ......

....there are often gaps in the walls, which give the colony a degree of flexibility as the supporting kelp frond bends in the sea currents. The gaps tend to be most conspicuous in older sections of the colony.

There are at least two kinds of zooid - the flower-shaped feeding lophophores and these translucent cylindrical forms.

I'm not sure what their function is but my guess is that they provide additional surface area for oxygen uptake or maybe waste disposal.

You can find out more about bryozoans here or take a look for yourself - these are low-power micrographs (maximum magnification x50) but you can see the living zooids with a hand lens if you put a piece of the colony in a shallow dish of seawater. You can find them all year-round and fine specimens are often attached to kelps that are washed up on beaches after storms.

Monday, December 7, 2009

The Ultimate Solar Cells

These green blobs are chloroplasts - in this instance packed inside the cells of a moss leaf and magnified around 400 times - upon which our collective future depends. Using only energy from sunlight, water and carbon dioxide from the atmosphere, they produce the oxygen we breathe, control the climate by removing carbon dioxide from the atmosphere and, directly or indirectly via plants and animals, produce all the food we eat. Currently 6.3 billion of us depend on them for our survival. By 2050 9 billion of us will need their services. Maximum respect for plants, then..... and, more precisely (see Psi Wavefunction's comment), chlorophyll, in all of its manefestations, wherever it occurs

Friday, November 27, 2009

A Marvel of Miniaturisation

Hard to believe, maybe, but inside a horse chestnut Aesculus hippocastanum bud like this there’s a whole year’s future growth, folded, packaged and ready to be unpacked at the first hint of spring......

A vertical slice through the bud reveals next year's spike of flowers inside, preformed, packed in mass of white hairs (the bud's equivalent of loft insulation), surrounded by an armour of overlapping bud scales and sealed in resin, protected against the rigours of the coming winter.......

Cranking up the magification a little more reveals the sectioned individual flowers. The pink lines around the buds are the sepals and petals, and the elongated yellowish objects inside are the stamens that will produce the pollen that next year's bumblebees will collect...

A transverse section across the flower bud reveals the individual flower buds (surrounded in pink) and next year's leaf stalks (the ring of green circles around the outside of the bud, just inside the overlapping, interlocking bud scales)....

... and at higher magnification in this transverse section you can see the pink sepals and petals of the flower buds a little more clearly. That convoluted wavy green line between the flower bud and the bud scale is the blade of one of next year's leaflets, tightly folded at this stage. The mass of white insulating hairs inside the bud coat the new leaflets when they emerge from the bud in spring, looking in their earliest stages like little furry fists. Something to look forward to.

For a reminder of what those microscopic flower buds will become, hop over to

... and if you want to look even further forward, to next autumn, and see what they'll produce, take a look at

... and for a look at some other buds from different  tree species, hop across to

Sunday, November 22, 2009

Polypody – the fern with the golden sporangia

Some polypody Polypodium vulgare ferns continue producing spores deep into winter and if you turn over a few fronds you’re eventually likely to find these golden cluster of sporangia. Unlike many ferns, the sporangia of this species are not covered by a membrane during their development and under the microscope they resemble nests of golden eggs, or maybe even party balloons if you're in a celebratory frame of mind.

Each sporangium is packed full of spores and when they’re ripe there’s a remarkable mechanism for catapulting spores out into the airstream, that you can read about at

The gaping sporangium at the top of this picture (above) has burst open and has already catapulted out most of its spores. You can still see the spores packed into the surrounding unripe sporangia, through their transparent walls 

Polypody spreads vegetatively with creeping rhizomes, that either grow over the branches of trees or through old walls, and you can see it in its habitat over at

Sunday, November 15, 2009

The Armoured Brigade

Every time I lift the lid of our compost bins to dump another load of kitchen waste a horde of woodlice scurry away in all directions, so I thought I’d catch one and take a closer look under the microscope. It turned out to be the common shiny woodlouse Oniscus asellus. Woodlice are terrestrial crustaceans – relatives of crabs, prawns and lobsters but more closely related to marine isopod (meaning that all the legs are the same length) crustaceans like the one portrayed at

Michael Chinery notes in The Natural History of the Garden (Collins 1977) that woodlice have acquired at least 65 local names, including sow-bugs, tiggy-hogs, sink-lice, slaters and coffin-cutters.

Woodlouse senses are centred around the jointed antennae and simple eyes that have only about 25 individual ocelli – probably enough to detect light and shade and largish moving objects, but probably incapable of forming images with a very high degree of resolution.

The tail segment of a woodlouse is called the telson, flanked by two appendages called uropods , and its shape is often an important species identification feature.

All woodlice have only six pairs of legs in their infancy (when they’re known as mancas) and the full complement of seven pairs, visible here, only appears after their first moult, a day after they’re released from the brood pouch of their mother who carries them around. From below you can see the mouth at the head end, between the antennae .

Woodlice are omnivores but will eat other small animals if they can catch them, so have two pairs of jaws – crushers at the front and lethal-looking pointed ones behind.

The armour is an obvious adaptation to surviving terrestrial predators like spiders but the woodlouse’s main problem is keeping moist, because it obtains oxygen by diffusion over these lung plates at the tail end. Generations of schoolchildren have conducted simple experiments offering woodlice a choice of moist or dry environments but the outcome is never in doubt – in a dry environment a woodlouse will suffocate, for lack of dissolved and diffused oxygen.

Tuesday, November 3, 2009

Swallowtail Scales

Like most long-established university biology departments, Durham University School of Biological and Biomedical Sciences has substantial collections of specimens that have been donated over the years, including a large number of butterflies ........... which offer an opportunity to explore one the the microscopist’s favourite natural objects – butterfly wing scales. These are the wing scales of a swallowtail Papilio macheon which in this old pinned specimen can't match the vibrancy of colour in the living insect portrayed below, but they are still exquisite objects. If you look closely you can see that they vary in shape as well as colour ... notice how the edges of the red ones are more indented than the blue ones. The metallic colours in butterfly scales are the result of optical effects rather than pigments and are produced by ultra-fine grooves in the scales, where light penetrates to different depths and the reflected light waves interact to produce the electric blue interference colours.

Sunday, November 1, 2009



A while back I posted some pictures of Hydra viridis (see showing its remarkable ability to change shape. The pond that I regularly use for collecting small freshwater protists and invertebrates is currently teeming with these tentacled hunters, so I took the opportunity to shoot this short video sequence of this elastic animal in motion.

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