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Feely fish, staircase angles, ‘Useless’ body parts
![A Fangtooth’s toothy mouth traps fish within sucking distance. [© 2004 David Wrobel, Monterey Bay Aquarium Foundation]](images/2004-11-12-fangtooth.jpg) Q: How do fish see and feed at depths beyond the reach of
light? (Ron, Sun City, CA)
A Fangtooth’s toothy mouth traps fish within sucking
distance. [© 2004 David Wrobel, Monterey Bay Aquarium Foundation]
A: Primarily by smell and vibration, says
Laurence P. Madin, biologist at the
Woods Hole Oceanographic Institution. Some also make their own light.
Smell. Fish smell with two nostrils,
one on each side of the head. Their sense of smell can be acute. Sharks, for
example, can detect smells 10,000 times fainter than a human can.
The deep-sea anglerfish (found in the inky black at 2200
yards, 2000 m) have extremely large nostrils and a powerful sense of smell.
Males can detect and follow the distinctive scent released by females of their
kind. A tiny male (about a half inch, 1.3 cm) finds a female (which may be 10
times longer than he), bites her, fuses his skin to hers, and lives off of her.
They grow together, even sharing the same bloodstream.
Vibration: hearing and feeling. Fish
hear sound vibrations with internal ears.
They feel water vibrations with hair nerves. The nerves are
either freely distributed on their skin and touching water or laterally along
internal lines the length of their bodies.
The free-vibration sensors tell the fish in which direction
it’s swimming. The lateral ones sense particulars of nearby fish motions since
the sensors receive a sequence of vibrations as the disturbance moves across the
fish. This enables the fish to detect prey over a short range and also to school
with like fish.
When a deep-sea Fangtooth feels a fish swimming nearby, it
opens its huge mouth and sucks the animal in.
Light. Other fish make their own
light to find food or escape being someone else’s food. Some, like fireflies,
produce light in special organs called photophores. Others rely on bacteria to
make the light.
The shiny black tubeshoulder, found in the deep night 1100
yards (1000 m) down, squirts a glowing slime, distracts a predator, and slips
away into darkness.
Further Reading:
Monterey Bay Aquarium: Survival in the deep
![Mountain “stairs,” southeast Alaska [John Bortniak, NOAA]](images/2004-12-03-steps.jpg) Q: At what angle do you climb, when you climb a flight of
stairs? (Sopuruchi, Port Harcourt, Nigeria)
Stairs rise at an angle between 30 and 35 degrees.
That’s steep enough to cause an avalanche on a snowy slope.
Mountain trails typically have gradients of 15, 20, and 25 degrees. For example,
a 2000-foot (610 m) vertical gain over a mile (1.6 km) of horizontal distance is
a 20-degree slope.
Further Reading:
Aubuchon Hardware: how to build outdoor stairs
Backpacker Magazine: Mountain miles
Himalaya, Inc: Pumori
Q: Are there any body parts of a human body that we don't use?
(Ashton, Pineville, Louisiana)
A: Probably not. Some parts matter more than others but even
the "useless" ones have value that we’re just learning about. We used to think
180 parts (for example, the thyroid, tonsils, appendix) were without function.
Now it’s down to maybe one — an internal tail — the tail bone. Even that
supports some abdominal muscles.
Indeed, until May of 2004, we believed 97% of the DNA that
makes up our complete chromosome set is junk. The "junk" DNA does not provide
code to produce proteins. Consequently, we deduced the DNA had no purpose at
all.
Then David Haussler of the University of California, Santa
Cruz noticed something downright peculiar. He found a huge number (480) DNA
regions of this so called "junk" DNA that is 100% identical for man, mouse, and
rat. Normally gene sequences for mouse and man average only 85% similar.
What, he wondered, was so critical to survival that creatures
for 400 million years of evolution maintained the exact, identical regions of
code?
He doesn’t know yet but that DNA is not junk!
To answer your question, let’s run through some likely
candidates for useless parts:
wisdom teeth — they often grow in crooked or
the opposing tooth doesn’t emerge so they end up useless for
chewing.
male nipples — useless, perhaps, but may exist
because natural selection can’t easily edit out their production
without messing things up for females.
the plantaris muscle — a calf muscle that
causes all toes to flex all at once for monkeys and thus helps
their feet swing from a branch through trees. In humans, the
muscle does not flex toes simultaneously and is largely useless.
Indeed, it is atrophied, may be totally absent and, when
present, does not even reach the toes.
Useless? Maybe. But...
"Just because you can survive quite well without something
doesn’t indicate that it’s useless," says
Gail Sullivan,
assistant research professor of medicine at the University of Virginia Health
Science Center. "You may be better off without a badly infected appendix or an
impacted wisdom tooth but, as is becoming apparent, this doesn’t mean that
healthy counterparts are ‘useless’."
Further Surfing:
WonderQuest: ‘Useless’ appendices
Wikipedia: Junk DNA
BioEd Online: ‘Junk’ DNA reveals vital role by Helen Pearson
(Answered Nov. 12, 2004)
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