“We’re watching a clock in the process of being broken.” — NiCHolAS S. FoulkeS
Cave fish follows
its own rhythm
A species of fish that has lived in
caves for millions of years has lost
its eyes—and may be losing inner
clocks that set body rhythms to
daily light-and-dark cycles.
By Tina Hesman Saey
A fish that swims in limestone caverns
under the Somalian desert has something to tell scientists about keeping
time. Despite living in permanent darkness, this blind cave dweller still has its
own quirky sense of rhythm.
The Somalian cave fish (Phreatichthys
andruzzii) has an inner timekeeper set
by food rather than sunlight that ticks
out a roughly 47-hour day, scientists
from Italy, Germany and Spain report
online September 6 in PLoS Biology.
This odd biological clock may teach
scientists more about the molecular
pathways that govern such clocks, why
clocks are important to organisms and
how living things adapt when their
clocks are no longer tied to cycles set by
the rising and setting of the sun.
The daily clocks of most animals,
plants and some kinds of bacteria follow
an approximately 24-hour cycle and are
reset largely by sunlight. These circadian
clocks help govern sleeping, waking and
feeding times, the rise and fall of blood
pressure and other daily rhythms.
Frogs make do with dew
During northern australia’s dry season, green tree frogs can
pull a drink out of thin air. Even on chilly nights, green tree
frogs (Litoria caerulea, left) turn up outside their cozy tree
cavities. New experiments show that water condenses on the
frogs when they hop back inside from the cold, Christopher
tracy of the university of melbourne in australia and colleagues report in the october American Naturalist. “they can
get a little bit of water, and that little bit of water might be very
important,” tracy says. frogs air-cooled to below 15° Celsius
accumulated 0.03 percent to 0.54 percent of their body mass
in condensation. the strategy is a trade-off for the animals,
however, because leaving a humid refuge for the dry, cold night
air increases water loss through the skin. using a computer
simulation, the team calculated that a frog would benefit if it
stayed outside only for the half an hour or so needed to chill
itself to the temperature of the night air. — Susan Milius
