|
Globe Scan:
Only half of world's spiders discovered
Spiders live in every continent, except Antarctica, and in many
environments, from rain forests and deserts to studio apartments.As
familiar a sight as these eight-legged creatures might be, there is
plenty we don't know about them. Scientists have described about 43,000
species of spiders, and Norman Platnick, the American Museum of Natural
History's "spiderman," estimates that just as many remain to be
discovered.
"Because these are only estimates, people disagree," Platnick, the
museum's curator emeritus of invertebrate zoology, said of estimates of
the unknown species.
"I have argued that we are basically halfway through [identifying the
world's spiders]. Some of my colleagues think I am being way to
optimistic and we are closer to only 20 per cent through. "To figure out
how many species remain to be discovered, scientists often look to
museum collections. Because finding and collecting a specimen takes much
less work than figuring out what it is, Platnick said, these collections
can accumulate unidentified specimens.
The spiders and other arachnids known to science so far are amazingly
diverse. A new exhibit, which opened on July 28 at the New York City
museum, explores this diversity and offers visitors the chance to get up
close with live spiders and a few of their close relatives.
These include one of the largest spiders, the goliath bird eater
whose prey includes snakes, mice and frogs; the western black widow, one
of the few spiders poisonous to people; as well as other arachnids,
including the desert hairy scorpion and the skunklike giant vinegaroon,
which sprays a vinegar-like chemical from its abdomen when disturbed.
Live goblin spiders, which Platnick is currently studying, are not on
display.
 Typically
about 0.08 inches (2 millimeters) long, these spiders are easy to miss,
and as a result were a particularly poorly known spider family.
In 2006, Platnick and collaborators from around the world began a
Planetary Biodiversity Inventory focusing on the goblin family,
Oonopidae. At the time, fewer than 500 species - an estimated 20 per
cent of the family's actual diversity - had been described. Today, that
number is more than 1,000, according to Platnick. Improvements in
microscope and imaging technology have made it much more realistic to
study tiny living things, he said. Most tiny spider species live on the
ground, so to find them researchers must scoop up soil and leaf litter
and sort through it using sifting or funneling devices and by hand. Some
have also been found living in tree canopies.
Like their spider relatives, many scorpions remain unknown to
science, said Lorenzo Prendini, a museum curator who studies scorpions.
About 2,000 species of scorpions have been described, but "there may be
at least double or probably triple the number of species remaining to be
discovered," Prendini said. "I say that because whenever we go to an
area, let's say in the southwestern United States or South Africa or
Australia that are relatively better known for scorpion fauna, and we
survey the area thoroughly and using a variety of modern techniques we
double or triple the number of species in the area."
Extrapolating out to the rest of the world, he estimates there are
between 4,000 and 7,000 scorpion species on the planet. It's not clear
where scorpions fit in the arachnid's family tree, since analyses
relying on anatomical or genetic data show scorpions branching off from
other arachnids at different points in Arachnida's evolutionary history.
"Because scorpions are so old as a lineage, as I mentioned 425 million
years old, and because they don't move around much, they are a very good
group for understanding how the Earth
The exhibit SpidersAlive! is scheduled to run through Dec. 2 at the
American Museum of Natural History in New York.
Courtesy: LiveScience |
