[Paleopsych] NYT: Observatory: Eat or Be Eaten (but Eat Right)

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Observatory: Eat or Be Eaten (but Eat Right)
NYT January 11, 2005

If it is hard for many people to eat balanced diets, given
the array of foods available, imagine what it must be like
for carnivorous predators. They eat only what they catch,
and what they catch is limited. The wild is no Las Vegas
all-you-can-eat buffet.

That is why scientists have theorized that for most
carnivores to stay healthy the composition of their prey
has to be nutritionally balanced. These carnivores do not
select prey for nutritional content, but rather optimize
the amount of prey they eat. Herbivores, by contrast, can
pick a fatty nut over a starchy root.

A researcher at the University of Oxford in Britain has
found some carnivorous predators that can pick and choose
nutrients. In experiments with three invertebrate species,
a ground beetle and two spiders, the researcher, Dr. David
Mayntz, and colleagues found that the predators actively
balanced their diets.

"All of them are trying to get the right nutrients, but in
different ways," said Dr. Mayntz, whose study is published
in the current issue of Science.

The three species have quite different feeding behaviors,
he said. The beetle is an active forager, hunting its food.
One spider is semiactive. It sits and waits for prey,
ambushing it as it ambles by, but can also move to another
foraging spot as needed. The other spider builds a web and
is totally dependent on whatever prey is caught in it.

Specimens of all three species were fed an unbalanced diet,
too rich in either fat or protein. Then they were watched
as other foods were made available. In all three cases, the
invertebrates opted for food that would make up what they
were lacking. That is, if they had first been fed
protein-rich food, they then consumed fat-rich food. "We've
shown that they have priorities and try to get what they
need," Dr. Mayntz said.

The effect could be seen, he added, even if the specimens
had been kept on an unbalanced diet only for a day. "When
you're balancing macronutrients, these things are often
short term," he said.

Dr. Mayntz said he would not be surprised if other
carnivorous predators, even large mammals, were someday
shown to have the same ability to balance diets. Leopards
might be selective about what parts of the prey, lean or
fatty, they eat right after the kill. "I would guess that
they would go for what they need first," he said.

Life in the Salt, Salt Sea

The environment around
deep-ocean hydrothermal vents is among the most
inhospitable anywhere, yet it is home to single-cell
microbes, tube worms and other organisms that like their
habitat hot and sulfurous.

But vent zones aren't the only extreme neighborhood under
the sea. In the eastern Mediterranean, for example, at
depths of 10,000 feet or more, are basins that in addition
to lacking light and oxygen are among the saltiest places
on earth. And there, too, a European team of scientists
report in Science, life exists.

The scientists were part of Biodeep, a project sponsored by
the European Community to explore these deep-sea basins in
the Mediterranean between Greece and Libya. This is a
region where the sea dried up more than 5.5 million years
ago, leaving vast salt deposits that were since covered in

When the sea returned, tectonic activity exposed the
deposits in certain areas, creating a hyper-salty brine. In
one of the basins, for example, the concentration of the
salt magnesium chloride is the highest found in a marine

Yet the researchers found an active microbial community in
the four basins they sampled with a robotic submersible.
Previously unknown species of bacteria as well as archaea
were discovered.

The researchers say their work shows that some microbes are
even more adaptable to salt than previously thought. And
they suggest that the findings lend more support to the
idea that life might exist elsewhere in the solar system.
Jupiter's moon Europa, for instance, may have pockets of
brine in its icy shell.

Sludge-Eater's Genome

It was discovered in lowly sludge from a sewage-treatment
plant, but now it's at the top of the heap, genomically
speaking. The genome of the bacteria Dehalococcoides
ethenogenes has been decoded by scientists at the Institute
for Genomic Research in Rockville, Md.

D. ethenogenes has the ability to naturally clean up
polluting compounds like the dry-cleaning solvent
tetrachloroethene (which is what it was doing when it was
discovered at the treatment plant, in Ithaca, N.Y.). The
genome for the bacteria (a variety called Strain 195)
contains about 1.5 million base pairs, about one-third to
one-fourth of the number of base pairs in strains of E.
coli that have been sequenced.

The sequence for D. ethenogenes, which was described in
Science, includes genes for fixing nitrogen and parts of
genes that fix carbon dioxide. This suggests the bug had an
ancestor that was a bit more conventional.

The work should help scientists learn how to better grow
the bacteria (which are difficult to culture in the lab)
and use them for environmental cleanup.

Supermassive Outburst

These are boom times for black
holes. In recent years, astronomers have detected large
outbursts of X-rays and high-energy particles from black
holes, caused by the acceleration and extreme heating of
gas clouds drawn to them by their enormous gravitational

Now, scientists using data from the Chandra X-ray
Observatory have measured the most powerful explosion yet,
from a supermassive black hole at the center of a distant
cluster of galaxies. The outburst has produced two enormous
cavities, measuring hundreds of thousands of light-years
across, as the emissions displace and compress the gas in
the cluster.

The researchers, led by Dr. Brian McNamara of Ohio
University, suggest that the energy required to create
these cavities - 6 times 10 to the 61st ergs, for those
keeping score - is nearly an order of magnitude greater
than the next-largest outburst ever detected. The work was
published in the journal Nature.

All that energy would tend to keep the gas in the cluster
from cooling down for several billion years, the
researchers estimate. And since gas has to cool and
coalesce to form new stars, the black hole would seem to be
preventing this from happening. The finding adds to a
growing body of evidence that may help explain why clusters
like this do not make new stars.


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