by Simon Barnes
Some years later, I was in Kenya writing about a humanitarian project that had been adapted by The Times as a Christmas charityIII and was visiting a spectacular health centre in the middle of Masai territory, run by a remarkable philanthropist called Anne Lurie. It was a privilege to be there, and I didn’t really need a reward, but I got one anyway. On one foray away from the health centre, to observe the outreach team visiting HIV-positive patients, gallantly riding across the bush on dirt-bikes, we came across some gerenuks,IV antelopes I had always longed to see. These are amazing things, dry-country antelopes as the lechwe are specialised for wet. They don’t need to drink; they get all their moisture from the vegetation they eat. They are slim and elegant even by antelope standards – they make the lechwe look positively chunky – but it’s the neck that makes them extraordinary. The head is perched on a neck of improbable length and elegance: they are like antelopes trying to be giraffes. Which just about describes their way of life: they can reach higher than any competing antelope species, and so they can take leaves that are beyond the reach of rivals. They not only have these exaggerated necks, but they can also stand up, with a vertical back, and browse in comfort on leaves 2 m, 6 feet 6 inches above the ground. With their antelope eyes and their unusual build, they are an affecting sight.
So much so that the Hollywood actor and big-game hunter William Holden shot one. He then examined his work close up and exclaimed: “I’ve just shot Audrey Hepburn.”V It wasn’t a joke: it was a moment of life-changing horror. It was also a classic Damascene experience: Holden became a conservationist, and set up the William Holden Wildlife Foundation, which runs an education centre for conservation in Kenya.
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I. There I go, boasting about the ferocity of a species or a population. It’s a natural human response. I am, irrationally, very proud of the ferocity of my lions. Even if they’re not actually mine. But perhaps the prize for pound-for-pound ferocity should go to the smallest carnivore, the weasel, which fearlessly takes on prey – rabbits – many times its own size.
II. A subspecies is a population that is significantly different from other populations of the same species, but not different enough to count as a separate species. It’s just one more part of the fuzziness of taxonomy. Birds are always being promoted from subspecies to full species, and sometimes back the other way. A recent example in Britain is the Scottish crossbill. It was a subspecies of the crossbill until 2006, when it was agreed that the songs of the two populations were significantly different, enough to make them two separate species, the Scottish and the common crossbill. This was fascinating stuff for taxonomists; for twitchers, who have a more sportive relationship with science, it was a thrilling development in their game. Overnight, those who had seen both subspecies had a new species for their lists: an armchair tick, in the jargon.
III. This was Riders for Health, which supplies motorcycles to health workers in developing countries, and, crucially, teaches them maintenance as well. Good people. Africa is full of expensive equipment that no one knows how to maintain: the 4x4 with grass growing through it is a frustratingly common sight.
IV. Hard “g”.
V. Hepburn and Holden worked together on Sabrina, 1954, and they were reunited for Paris When It Sizzles in 1964.
Life in the round
It’s an odd thing, but the larvae of starfish and the rest of the echinoderms look like the embryos of vertebrates. And in fact, this phylum is comparatively close to our own. It’s no surprise, then, that like ourselves the larvae are bilaterally symmetrical: we are all left-and-right creatures. We vertebrates grow up to become bilateral adults, but the adult echinoderms take a radically different direction. They live life in the round. They go in for radial symmetry. Mostly in a five-part way: where Shakespeare wrote his plays in iambic pentameters, echinoderms go in for pentamerism. The classic starfish body plan involves five limbs.
And that simple fact seems to me to enclose all the mystery of life. As a boy I was in thrall to the mystery of echinoderms: the compellingly alien round-and-round way of living was in itself a sermon on nature’s eternal inventiveness. I longed above all things to possess the skeleton of a sea urchin: the hard, hollow, spineless dome that a sea urchin leaves behind when the rest of its body has decayed and been consumed, a skeleton that makes some of the most satisfactory fossils, wonderfully pleasing to hold in the hand. You could buy table lamps made from skeletons of the larger specimens of sea urchin. Strange thing: I can’t remember if I ever, in fact, acquired a skeleton for myself. Perhaps I did long after the obsessive part of the desire had waned: a satisfying Proustian experience of disappointment, no doubt. Certainly the longing was by far the most vivid part of the experience: and that, I suppose, is what collecting is all about. Acquisition is always something of an anticlimax. (Faust and Don Giovanni both said something along the same lines.)
Echinoderms include groups that look superficially dissimilar, though that’s true of most phyla, our own included. As well as starfish, and the even more agile and mobile brittle stars, the phylum also contains mostly stationary groups like sea cucumbers, sea urchins, sand dollars, feather-stars and sea lilies. There are around 7,000 species altogether, and they are the largest marine phylum that has never diversified into fresh water, still less the land. They are diverse ma non troppo, a relatively conservative phylum that sticks to what works. And within these limits they are genuinely remarkable.
This five-way radial symmetry is the basic body plan but they have no great problems in deviating from it. There are starfish with six and seven arms, some with as many as 20. Some of the lilies – which like sea anemones look more like surreal plants than animals – can have 200 petal-like arms. Echinoderms use imaginative and various techniques for feeding; starfish are active hunters, cucumbers roll about on the sea floor and filter-feed on detritus, basket-stars feed on plankton. Most echinoderms favour the sea bottom, from the intertidal zones to the abyssal depths. The floor of the ocean is their domain and they have come up with a series of highly effective ways of exploiting it. Many of these sea-floor areas are low on life, but echinoderms are very talented at making the place work for them.
They confound our understanding of life’s possibilities in two quite different ways. In all living things liquids are transported via the vascular system: sap, in the case of plants, blood and lymph in our own case. Echinoderms have a vascular system that operates on water. Uniquely, they operate on hydraulics, a system that is brilliant, economical and highly effective. Why didn’t we think of that? But if we had done so, it’s possible that we wouldn’t have been able to break free from the watery life: we would have been forever barred from the land. From such accidents does the history of life unfold.
The second, rather more enviable development of the echinoderms is regeneration. If they lose a bit of themselves, they simply grow it again.I A starfish can lose one of its five arms and grow another. Some species will intentionally detach an arm, from which an entire new individual will develop: a particularly dramatic form of asexual reproduction, though echinoderms are perfectly capable of reproducing sexually. Sea cucumbers can discharge some of their internal organs as a defence mechanism; after they’ve done so they grow them back while surviving on nutrients stored in their bodies. Sea urchins regularly replace lost spines: this explains how some species can operate with such long and brittle appendages. The idea of replacing bits of yourself when they grow less effective has long been a human fantasy, though not necessarily a comforting one. Wearing out is our human birthright: echinoderms don’t see the world in the same way at all. Lose a limb? Plenty more where that came from.
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I. Some vertebrates can operate limited forms of regeneration: see the section on axolotls on page 394.
Do I know you?
We tend to find the idea of being mammals a trifle dismaying. It’s not something we like to think about. But we find it comparatively easy to deal with the idea that we are related to m
ammals. We can see some kind of kinship with a dog, a cat, a horse, a lion, an elephant. But when we get to animals further away from our notions of what a mammal should be, we find it rather more challenging. The fact that some of our fellow mammals lay eggs, for example, and that a mammal can carry poisonous spurs, are rather troubling; we will meet both very shortly. Marsupials that give birth to little blobs and nurture them in a pouch also stretch our minds somewhat: it is hard to think of ourselves as second cousin to a grub. But the creature furthest from human notions of what can possibly be a fellow mammal is surely the naked mole rat, and I introduce them here so we can get a real idea of what diversity means – diversity even in the class of animals that we belong to ourselves.
The naked mole rat, and its relation, the Damaraland mole rat, are the only species of eusocial mammals. That is to say, they live like termites, which we shall meet on this page. They are found in Ethiopia, Kenya and Somaliland and they live in colonies. Each colony has a queen: the queen is the only female that reproduces, though she may have up to three males to fertilise her. She can give birth to as many as 28 pups at once. The colony can hold up to 300 individuals and as few as 20; the average is 75. The naked mole rat is up to 10 cm, 4 inches, long and weighs around 35 grams, 1.2 ounces. Apart from the queen and the fertilising males, the rest of the colony is sterile. The smaller ones gather food and maintain the nest. Naked mole rats live on underground tubers. They look after them, so that they regenerate and provide food for months, sometimes even years. The larger workers defend the nest. The queen can operate for as many as 18 years, normally giving birth to a single litter every year. She will not tolerate other females who behave like queens and will suppress them violently. When she eventually dies there is a power struggle among the top female workers, and one will eventually take over, generally after a violent battle for the mastery, or rather the mistressy. She will then stretch out her vertebrae and so prepare herself for the task of giving birth and nursing young.
They are rodents, as you’d guess from their almost horrifically prominent teeth: they look like a pair of teeth animated by a pink sausage, for they are pretty well hairless. They live entirely underground and dig with their ever-replenishing self-sharpening teeth. They have powerful lips that form a seal behind the teeth so they don’t accidentally ingest earth. They move as fast backwards as they do forwards: useful for tunnel-life, when you can’t always make a three-point turn. They have small lungs but are very efficient at taking up and using oxygen: important adaptations for the oxygen-poor environment of a tunnel. Uniquely among mammals they are thermoconformers, not thermoregulators, which means they can’t dictate their internal temperature as we do, and so they move around the burrow to cope with changes in temperature, shifting to cool parts when it’s warm, and huddling together when it’s cold.
Another oddity: they lack the chemical – substance P – that transmits pain from the skin to the brain. They feel no pain when they encounter acid or pepper-spray. They are also remarkably long-lived. They can live 28 years, longer than any other rodent, and have a strong resistance to cancer. They also have an ability to slow down their metabolism in times of shortage. Work is being done to map their genome with a long-term view to improving the lot of humanity.
So here are two species of mammal whose way of life is weirder than we can imagine. And they are part of our own class in the Animal Kingdom. They are our own kind: and yet they are as alien as anything else we will encounter in these pages.
Flatworm, flatworm, burning bright
Blake asked his burning tiger: did he who made the lamb make thee? Earlier in these pages, David Attenborough – no less a genius – asked of the Loa loa worm: did he who made the hummingbird make thee? And now I must ask of the schistosomiasis-causing genus of trematode flatworms: did he who made the black and yellow flatworm Pseudoceros dimidiatus make thee? The phylum – or the various phyla, depending on what sort of taxonomist you are – of flatworms brings together the beautiful and the damnable in a manner that is disturbing and dramatic even by the standards of the Animal Kingdom. There are endless forms most beautiful, there are also endless forms most terrible. Sometimes the two classes coincide in fearful symmetry. Sometimes the beauty seems almost impossibly benign; at other times the creature that stands before you is so uncompromisingly terrible that every human being must struggle to cope with the very fact of its existence.
There are 20,000 species of flatworms so far described. They have no blood system and no organs for breathing; they use their entire body surface for absorbing oxygen. This is not a trick restricted to inverts; some species of frog do it too. It makes sense, then, to maximise the acreage of body surface for absorption purposes, so that’s why flatworms are flat. The smallest species have no gut either and take in food the same way they do oxygen, by absorption; the larger ones have a branching gut that reaches all tissues.
To a taxonomist they are specially fascinating creatures because of their bilateral symmetry. The invertebrate groups we have already looked at in these pages, the sponges, corals, anemones and jellyfish, all demonstrate radial symmetry. We tend to rate bilateral symmetry rather higher, not least because it is the body plan we work with ourselves, along with most of the Animal Kingdom. Flatworms are about as simple a living thing as can exist with this split-down-the-middle symmetry. They have a head end, to use the term approximately. Experiments have shown that they are capable of learning and remembering. Some species are capable of regenerating if cut in two.
And some of them are lovely things, rippling and featherlike as they glide their way through the water, sometimes in sumptuous colours, iridescent blue, deep crimson, purple, black and yellow, speckled with gold, so that you wonder about a world that can produce, apparently quite casually, a creature so obscure to us humans, and yet so gorgeous. This unexpected beauty of creatures that can be bigger than your hand is somehow deeply reassuring: benign creatures in a benign world.
The Turbellaria are a free-swimming group of 4,500 species, and they generally make a living by scavenging among the detritus, though some do so by direct predation. They possess ocelli, light-awareness organs too basicI to be dignified with the name of eye, with which they can detect the direction of light. Some species have one pair, others have three, though some species have clusters of them. They are hermaphrodites: in some species their courtship involves a bout of penis-fencing; the loser takes the female role.
Most of the free-living flatworms live in water, fresh or salt. A few can operate in damp soil and beneath logs. A couple of planarian species have been introduced to countries where the imported giant African land-snail has gone feral and become a pest. These flatworms preyed on the exotic and destructive snails in a very satisfactory way; alas, they stayed on and have started eating their way through native snails: oh, what a tangled web we weave when first we start to mess about with the natural world. This is a pretty terrible error: but it’s not as terrible to us as some of the things we find when nature has not been buggered about with at all. And flatworms can be truly terrible.
Some species release eggs into fresh water by means of an infected human. The eggs hatch on contact with the water, and release free-swimming forms. These infect snails. They then take on another form inside the snail, and after that, they divide. From the snail, they release another free-swimming form, and this infects humans and some other mammals. They enter through the skin, and then progress to yet another stage. After that they migrate towards the lungs, where at last they reach an adult stage. From there, they migrate to a favoured body part: it might be the bladder, the rectum, the intestines, the liver or the spleen, or they might stay in the lungs. They feed on red blood cells and produce eggs: some species as many as 3,000 in a day. They don’t often kill their human hosts – that, after all, would be counter-productive, like killing off your own planet – but they make sure their host feels like shit forever. This is schistosomiasis, sometimes called bilharzia, and the problems it causes ar
e not lethal but chronic. You can carry on living, but your life is always ever so slightly awful, unless you get treated.II The parasites can, however, be a factor in bladder cancer. When children are infected, the parasites can affect growth and cognitive development.
