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Science Frontiers ONLINE No. 115: Jan-Feb 1998 |
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A Strangely Selective Spider
Australia's funnel web spider is one of the world's deadliest. Before an antivenin became available, this species killed one human every four years. It is not this low death rate that impels us to mention this spider. It is because the bite of the funnel web is deadly only to insects and humans. All other mammals are said to be immune. Analysis of the venom yields the remarkable fact that it consists of 45 active compounds. One of these is specific to insect brain cells; another, to human nerve cells.
(da Silva, Wilson; "Spider Gives Kiss of Death to Pests," New Scientist, p. 23, May 17, 1997.)
Comment. Since humans are not on the funnel web's menu, it must be only a coincidence that its venom kills people so selectively. It would be nice to know if chimps, gorillas, and orangs really are immune.
A related phenomenon is seen in the venoms of cone shells. These snails are much more dangerous to humans, particularly naive shell collectors. Their venoms are extraordinarily complex and contain hundreds, perhaps thousands, of toxins. Many of these are specific to potential prey. Once again, humans are not on the menu but are included anyway.
(Concar, David; "Doctor Snail," New Scientist, p. 26, October 19, 1996.)
Comment. Both cone shells and the funnel web spider seem to possess venom factories capable of concocting wide ranges of toxins, even though some are of no practical use. Whence this amazing versatility in sophisticated chemical synthesis; how did these extraordinary glandular factories evolve?