Dry Storeroom No. 1 (31 page)

Diatoms are still an active field for research. They cross over into palaeontology, too, because their glassy skeletons have a good fossil record. David Williams is the current diatom guru, a man who carries the art of lugubrious gloom to humorous extremes. He has been working in Lake Baikal, the huge freshwater body in Russia, and a centre of endemic evolution. This study is in collaboration with University College, London, and the Limnological Institute of Irkutsk, and it is a good outcome of funding by the Darwin Initiative. The museum in London has put a lot of effort into projects under this heading. The Initiative was announced by John Major, then Prime Minister, at the Earth Summit in Rio in June 1992. It provides grants to help towards conservation of biodiversity, particularly if there is an element of sustainable development. It is intended to help developing nations, or areas where British expertise would be useful. Botanists from South-east Asia and South America have been trained up as taxonomists on Darwin money. I am sure the grand old man would have approved of this particular use being made of his name.

Lake Baikal, where diatoms, among many other organisms, have undergone a separate evolution

Lake Baikal is the world’s oldest lake; in one form or another it has been around for about thirty million years. This accounts for much of its biological uniqueness, for there has been time enough for evolution to work its creative wonders. It is also the deepest lake anywhere—1,637 metres at most, so there is ample opportunity for organisms to become adapted to different depths. There are probably more than 1,500 species unique to it, nobody is sure yet of the final number. The lake holds 20 per cent of the world’s freshwater, and, since water is likely to be the most important political issue in the twenty-first century, I suspect that the world at large will become much more familiar with Lake Baikal than it is now. David Williams and his colleagues have been scraping diatoms off the stones around the edge of the lake for several years—it gives David an excuse to be gently mocking about how he spent his summer: “scraping stones,” he says mournfully. They have added many species of diatoms to the lake’s biological inventory—there may be more than five hundred species, of which up to half may prove to be endemics. Like so many other organisms, diatoms also evolved in isolation in Baikal. But there are some diatoms, like
Eunotia,
that have species known elsewhere; these reveal some interesting patterns in biogeography. There proved to be a number of taxa in Baikal that were known widely around the Pacific Rim, even as far away as Vietnam, and the western United States. In some cases, however, these species were known only as fossils. They must have become extinct locally, but persisted in Lake Baikal. It seems probable that the distributions of the species we see today are related to ancient geographical distributions—ones that pertained even before the last ice age. The present species ranges are like a ghost of this former world. But evolution continued its work on the survivors to produce a series of species peculiar to Lake Baikal. The biological world never stands still: sometimes it is the smallest organisms that help to reveal the dynamics of our mutable biosphere. Few people even know that diatoms exist, yet the stories they have to tell may chart shifts of climate that are crucial to understanding how the world came to its present state. That is why it is so important to support experts in small and less showy organisms—they may be less glamorous than orchids, perhaps, but tiny diatoms may yet be informative of great matters.

I admire the botanists whose work I have described in this chapter. A different selection of people would have been just as admirable—but then, this book is my personal museum, and does not pretend to be comprehensive. I admire the way botanists respect more than two hundred years of taxonomic enterprise; I admire their commitment to improving botanical knowledge in countries less privileged than Europe or the United States. For every scientist I have mentioned there is a curator quietly working away on the herbarium. I think of Arthur Chater, a relentlessly modest man and prolific curator of specimens. As a young man he was coupled with Ted Hughes as one of the young writers published by Faber and Faber. He became an authority on coins, such as those minted in Aberystwyth under Charles I, of which he made the best collection. Some ten thousand of his many photographs of Welsh tombstones and other monuments are safely held in the Archives Network for Wales—and all carefully catalogued by Arthur Chater. It is impossible not to admire such versatility, such unfussy distinction.

I have to mention Dr. Norman Robson, too, if only to make amends. A few years ago I escorted Bill Bryson on a tour of the Natural History Museum for his book
A Short History of Nearly Everything.
Like millions of others, I enjoy Bill Bryson’s humour and powers of observation: one of his books helped me to survive during a particularly depressing visit to Kazakhstan. During his visit to the Museum we met Norman Robson, and I explained that he had spent practically his whole working life on
Hypericum.
When the account appeared in Bryson’s book, it seemed that Norman had spent his whole life studying a single species. In fact, the St. John’s wort genus
Hypericum
comprises hundreds of species (460 at last count) spread around the world, including some species that are almost trees and others inconspicuous trailing herbs. Most have attractive star-like yellow flowers. Some species are of horticultural interest, others are poisonous to livestock, and others again seem to be as effective as conventional medicine in treating depression. They are currently under investigation by pharmaceutical companies. By any reckoning
Hypericum
is an important group of plants. Sorting out the many species of
Hypericum
is, truly, a lifetime’s work. Norman is eighty years old, and has almost finished the task of completely revising the St. John’s worts, down to the last small creeping weed, well after most people are beginning to find pruning the roses rather more than they can manage. He is a Scotsman of unwavering gentlemanliness. I have been feeling guilty about inadvertently giving the wrong impression of his worth ever since that visit, so let me state it clearly: the man is an unsung hero.

The relationship of the Natural History Museum Botany Department to Kew Gardens has been touched upon, but it should be added that Kew extends the virtues of the museum to embrace living collections, a place where vulnerable species can be coddled into survival. Plants, fortunately, can be rescued from extinction even if only a tiny population remains in the wild. The lust for rare orchids and their consequent over-collection in nature gives places like Kew Gardens an importance that outstrips their modest acres. It requires a marvellous skill on the part of the orchid man at Kew to raise these most difficult plants from their tiny seeds. The idea of a living ark is not one I wholly favour, lest it release the moral pressure on politicos and businessmen and developers to preserve natural habitats. Plants and animals belong under the sky, not in glasshouses and vivaria. But with this reservation: the efforts of these dedicated scientists to slow the extinction process that environmental degradation and climate change have brought upon the world must be applauded. The Millennium Seed Bank Project takes the whole conservation business a step further. By first drying and then storing them under cold conditions, seeds can be preserved for many years. The intention is to keep secure the seeds of something like 42,000 species by 2010. Kew and the Natural History Museum have pooled their taxonomic expertise for the good of the biosphere. Let us say the Project is an insurance policy against the destruction of habitats that a wise stewardship of the planet should never let happen. It is depressing that there probably will be no end to such destruction, for tropical forests and other habitats are still being destroyed despite the efforts of conservationists, sometimes at great personal cost, as in Brazil. It is a sad fact that to many people the loss of a plant species is of less moment than the loss of a football match. I hate the thought that the only record of a beautiful plant might yet be the grave of the herbarium sheet.

6

Multum in parvo

Martin Hall is far too modest a man to claim to have saved Africa from disaster. But that is what his knowledge of some of the less salubrious members of the Class Insecta has accomplished. He knows a lot about screw worms. These insects are members of the Order Diptera, which are so called because their wings have been reduced to two—whereas nearly all other insects have four wings arranged in pairs (
pteros
is Greek for wing, as in pterodactyl,
di
is two). The hind pair of “wings” has been transformed into specialized peg-like balancing organs called halteres. In common parlance dipterans are flies. Those of us with cats will at some time have had the experience of finding a dead bird in the house, under the bed perhaps, all heaving with maggots. These particular dipterans are nature’s garbage disposal officers. We should, I suppose, be grateful to them for their useful work, but the more usual reaction is a convulsive shudder—maybe this derives from an instinctive response to warn us against eating bad meat. My father had fishing-tackle shops, and sold maggots to fishermen; they were known by the euphemism of “gentles” and came plain or coloured. “Half a pint of gentles—plain” was the commonest order. When I was helping in the shop I had to dig my hands down deep into the struggling mass. They were supplied to the trade by a farmer known simply as Wormy (he bred worms, too). I once went to his run-down farm on the western edge of London, in a bleak area that could not decide whether it was still countryside or just biding its time to become a cheap suburb. The worst moment was being shown the place where the gentles came from: a sealed room full of rotting carcasses, dripping profitable maggots. A scene like that would test the nerves of any budding naturalist. But it gets worse.

Cochliomyia hominivorax
—the New World screw worm fly. This adult was reared from a larva that came to the United Kingdom with a woman who had visited Trinidad and Tobago.

If feeding on decaying flesh is a good option, evolutionarily speaking, because flesh is nutritious stuff, it is only a small step to cut out the middleman—death. Feeding on
living
flesh is a logical progression in the dipteran way of doing things. Get in early, before the next fly. There are about two hundred species of flesh-eating flies. Martin Hall can identify their maggots within a couple of minutes, or so he tells me: to you or me maggots are just wriggling, pallid little tubes, but to Martin they are almost like old friends. A fly will lay its eggs in a vulnerable area—often a nice, moist place like around the lips, eyes or fundament. Then the larvae can hatch out and get to work. This habit may have come about by way of an intermediate stage whereby maggots consume bad and infected flesh around wounds—nasty but nourishing. These kinds of maggots have enjoyed a new lease of useful life recently, because they eat only rotten flesh and leave good muscle nearby untouched.
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They even secrete some chemicals that encourage the formation of scar tissue. For those who have developed tolerance or allergies to antibiotics, a treatment by “maggot therapy” is being applied for the first time since the First World War. The maggots are sealed in a box fixed over the wound, and all the patient feels is a tickling sensation as the little hygienists get to work. When all the bad flesh has been consumed, the box is unstrapped and the contents disposed of. However, the next evolutionary stage—the exploitation of living flesh—is much less benign. Consider the Cameroonian tumbu fly (
Cordylobia anthropophaga
). The species name alone may furnish a clue. This unpleasant creature lays its eggs in places where it can smell the merest hint of urine. The larvae form “warbles” in the flesh of the victim in the most sensitive parts of the body. For some time humans were infected by way of eggs laid on the gussets of knickers hanging out to dry—providing direct delivery to the right kind of protected habitat. When the little beasts got to feeding, the pain and embarrassment can be readily imagined. Modern hot steam irons applied to the garments in the right place have helped to see off this intimate curse.

The screw worm takes the grisly story of being eaten alive a little further. The “screw” that gives the worm its name is actually a series of concentric spines. The maggots operate as a cluster: they secrete an extra digestive enzyme within the wound to smooth their progress into the flesh by turning it into soup. The barbs of the spines interlock so that the maggots cannot be dislodged by the rasping licks of an ox tongue. As the maggots move inwards they continue to breathe through their stubby back ends by means of spiracles—the openings to these “lungs” can be seen as tiny dark dots. The definitive screw worm is a New World fly,
Cochliomyia hominivorax
(the species name is the Latin equivalent of the Greek
anthropophaga
of the tumbu fly), which is particularly prevalent in Mexico and central America. It can progress from larva to pupa in under a week, and since an adult fly can travel many kilometres and lay thousands of eggs, these flies can quickly become a plague. They can reduce a cow to pulp. Even where the fly is native it is a scourge, but if it escaped into a place where animals were unprepared for it, the consequences could be disastrous. As its scientific name implies, the screw worm can feed on humans, too, in a comparable fashion. This is how it was first discovered. The French entomologist Charles Coquerel described the species in 1858 from a specimen taken from a man who died at Cayenne, the infamous penal colony in former French Guyana. It is in all our interests to stop the spread of this alarming creature, which is the point at which Martin Hall comes back into the tale.

The feeding head of the larval screw worm
Cochliomyia

In 1989 Martin Hall went to Libya and found screw worm larvae in the herd belonging to the Ministry of Agriculture. He told me it did not take him more than a few seconds to recognize the characteristic dark spiracles of
C. hominivorax.
The parasite had probably been introduced from South America in imported sheep. The Libyans did not like his diagnosis at all, and Martin was forced to raise some of the maggots in his hotel room to prove his point. He is not the type of man to let his expertise be challenged. Imagine if the screw worm were allowed to escape into Africa unchecked. Not only would domestic cattle suffer appallingly, but the fly would have wrought havoc on all the wild bovids across the continent, all those wildebeest and hartebeest and their relatives. The infestation could well have pushed rare species into extinction. It would have been an unprecedented catastrophe for an already blighted continent. In the Libyan context it was particularly galling that a common name for the parasite is the “American screw worm”—paranoid explanations of the infestation were bound to follow. Something had to be done to eliminate the pest, urgently. The technique used was sterilization. The idea was to release vast numbers of sterile male flies into the wild among the herds. If enough were liberated in this way, the chances of a female coming across a fertile male would be small; mating would lead to duff eggs at best; repeat the process several times and the viable breeding population would shrink to nothing. The crisis would be averted. The technique used involves sterilizing the males at a late pupal stage, by exposing them to a radioactive isotope of the element Caesium Cs
¹³⁵
. This is late enough in the development of the insect to produce a male normal in all other respects, including sex drive. The figures are extraordinary: sixty
million
pupae a week were air freighted from Mexico to Libya during the eradication programme. The logistics of producing so many maggots and pupae require that they are fed on massive quantities of a rather unpalatable meat pâté, a case of Wormy writ very large. Sterilization as a biological control was invented by Edward Knipling, whose name should feature with those of Edward Jenner and Louis Pasteur in the pantheon of those who rescued humans from misery. In 1995 was awarded the Japan Prize, which is almost the same as a Nobel, though less well known outside the scientific
cognoscenti.
As for the Libyan outbreak, the release of sterile males was continued until six months elapsed without capture of a fertile fly. With one bound, and billions of pupae later, the cattle were free. All this was achieved because an expert knew his maggots…The outcome is a plaque in the Food and Agriculture Organization of the United Nations, and the screw worm is now a “notifiable” pest at the Office of International Epizoology in Paris.

The price of freedom from flesh-eating flies is eternal vigilance. The kind of molecular evolution studies that we have already met in describing schistosomes confirm what many entomologists had suspected: that this nasty behaviour has arisen several times from different ancestral flies. The carnivorous flies in question appear on separate branches of the evolutionary tree, cousins under the skin. The Old World screw worm is called
Chrysomyia bezziana
(“Bezzi’s fly”—and who would like such an animal named after him?) and learned its grisly trade independently of its New World counterpart. It is a native of sub-Saharan Africa and Asia. This species particularly infects open wounds, burrowing in using special hooks, and if such lesions are left untreated the parasite can cause permanent disfigurement. It is not averse to burrowing into soft fleshy folds elsewhere on the anatomy, rather like the gusset fly.
Chrysomyia
has arrived in the Middle East: in Iraq between the first and second Gulf Wars; in Bahrain, probably on shipments of sheep brought in to feed a growing population. Imported Arab horses are another possibility. Of the four horsemen of the apocalypse, only pestilence could be carried on the steed itself.

There are, of course, lesser parasites. The louse is an inconvenience rather than a death sentence. “Lousy” as an adjective does not rate as the absolute nadir; it’s more of a generally disgruntled word, a crosspatch’s rejoinder to a formulaic question about the state of his health.
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The human louse has been having a lousy time of it in western countries since the 1950s; once ubiquitous, the head louse hangs on persistently in schools, and still sends a shudder through a mother who finds its “nits” (egg cases) on her children’s hair. The louse was named scientifically, it will be unsurprising to learn, by Carolus Linnaeus himself:
Pediculus humanus.
There are two different subspecies, living on head and body (
capitis
and
corporis
) respectively; the pubic louse (“crabs”)
Phthirus pubis
is more distantly related. In nature there are some five hundred other species of lice living on many other hosts. One of the curators at the Natural History Museum responsible for lice was Bruce Frederic Cummings, who joined the staff in January 1912. He had—too grim for irony—a lousy time. He was dying from multiple sclerosis, what was then known as disseminated sclerosis. He was forced to resign from the Museum in 1917 because of ill health. But he recorded his struggle with decline in a remarkable memoir compiled from his diaries. His extraordinary account was published in March 1919 under the title
The Journal of a Disappointed Man.
Cummings wrote under the nom de plume of W. N. P. Barbellion. The initials W. N. P. stood for Wilhelm Nero Pilate, the author’s selection of the most despicable people in history; Wilhelm was of course Kaiser Bill, this being the time of the First World War. Barbellion was a name emblazoned above a shop in South Kensington that Cummings passed every day. The
Journal
is a work of introspection so intense and unflinching that it leaves the reader exhausted. There is fury at his loss of hope, but since Barbellion was incapable of turning a dull phrase the text is also somewhat exhilarating. Of his wasting disease he writes: “Why this deliberate, slow-moving malignity? Perhaps it is a punishment for the impudence of my desires. I wanted everything so I get nothing…I am not offering up my life willingly—it is being taken from me piece by piece, while I watch the pilfering with lamentable eyes” (5 July 1917).