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        Biodiversity is not just a matter of tigers and whales，or butterflies and trees. It is also about  21  creatures too small to see that live in numbers too large to count in ways too numerous to imagine. In that  22 ，the discovery by Curtis Suttle of the University of British Columbia and his colleagues of a critter they propose to call Cafeteria roenbergensis virus, or CroV, should not be surprising. CroV is not a very virus-like virus. It has 544 genes，compared with the dozen or so that most viruses  23 . Also, it may be able to make its own proteins—a task that viruses usually delegate to the molecular machinery of the cells they infect. 

        CroV, as its full name suggests, is a parasite of Cafeteria roenbergensis, a single-celled planktonic organism that was itself discovered only in 1988. Despite the recentness of its discovery, C. roenbergensis is one of the commonest creatures on the planet. It is also reckoned by some,  24  it hunts down and eats bacteria, to be the most abundant predator on Earth. It is found in every ocean. The samples of C. roenbergensis from which Dr Suttle and his team extracted their quarry were collected off the coast of Texas. 

        Those who like their categories   25  may wonder whether viruses are alive or not. Wise biologists do not struggle too much with such questions. Viruses have genes, can reproduce and are  26  to the evolutionary pressures imposed by natural selection. That is enough for biology to claim them. As for CroV, those 544 genes (  27  730,000 base pairs, the DNA letters in which the language of the genes is written) mean its genome is bigger than those of several bacteria~creatures which everyone agrees are alive. 

        The problem with categorical thinking in biology is that evolution does not work like that. It actually works by whatever works working. If an organism can successfully  28  part of the business of metabolism to another while retaining the rest itself, rather than offloading the whole lot as most viruses do, then there are no rules to stop it happening. CroV seems to do just that. Besides the genes that relate to protein synthesis，it has others encoding DNA repair mechanisms  29  those involved with protein recycling and signaling within cells. This is not mere hijacking. It is tantamount to a complete personality transplant for the infected cell. 

        A whole new chapter of life，in other words，has been opened This discovery，then—and the earlier one of C. roenbergensis itself—speak  30  , albeit in a microscopic language, about biodiversity. Two centuries after Carl Linnaeus invented the system now used to describe it, and a century after Charles Darwin worked out what causes it, the ability of that diversity to surprise is still .

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