Wild Three-Toed Sloths Sleep 6 Hours Less Per Day Than Captive Sloths, First Electrophysical Recording Shows

Source:

http://www.sciencedaily.com/releases/2008/05/080513191934.htm

ScienceDaily (May 14, 2008) — In the first experiment to record the electrophysiology of sleep in a wild animal, three-toed sloths carrying miniature electroencephalogram recorders slept 9.63 hours per day--6 hours less than captive sloths did, reports an international team of researchers working on the Smithsonian Tropical Research Institute's Barro Colorado Island in Panama.

"We are fascinated that some species sleep far longer than others. If we can determine the reasons for variations in sleep patterns, we will gain insight into the function of sleep in mammals, including humans," said first author Niels Rattenborg, group leader of the Sleep and Flight Group at the Max Planck Institute for Ornithology. "If animals behave differently in captivity (where all previous comparative studies were performed) than they do in the wild, measuring their brain activity in captivity can lead to the wrong conclusions."
The research team got around this problem by using a technique developed for monitoring brain activity in humans in conjunction with a newly developed miniature recorder for neurophysiological data in order to monitor sleep in the wild.
In addition to two brain activity sensors worn as a cap on their heads, three adult three-toed sloths, Bradypus variegatus, also were fitted with radio-telemetry collars and accelerometers so that their exact locations and movements could be monitored during the next three to five days. The activity of two other sloths was monitored via radio-telemetry collar alone, for approximately seven months using a unique Automated Radio Telemetry System in place on the island.
The placement of sensors on sloths living in treetops demonstrates the feasibility of understanding a complex behavior, such as sleep, in the intricate tropical forest environment. It also will lead to more refined, comparative sleep research.
"The beauty of the automated telemetry system is that it makes a new suite of animal behavior studies possible," said Martin Wikelski, director of the Max Plank Institute for Ornithology, researcher at Princeton University and research associate at the Smithsonian. "We certainly encourage researchers who would like to monitor animals in the wild to join our ongoing studies or initiate work using the system."
Authors represent the following institutions: Max Plank Institute for Ornithology, University of Ulm, University of Zurich, New York State Museum, Princeton University, e-obs Digital Telemetry and the Smithsonian Tropical Research Institute.

Fausto Intilla - www.oloscience.com

Female Concave-eared Frogs Draw Mates With Ultrasonic Calls

Source:

http://www.sciencedaily.com/releases/2008/05/080511190843.htm

ScienceDaily (May 12, 2008) — Most female frogs don't call; most lack or have only rudimentary vocal cords. A typical female selects a mate from a chorus of males and then --silently -- signals her beau. But the female concave-eared torrent frog, Odorrana tormota, has a more direct method of declaring her interest: She emits a high-pitched chirp that to the human ear sounds like that of a bird.

This is one of several unusual frog-related findings reported recently in the journal Nature.
O. tormota lives in a noisy environment on the brushy edge of streams in the Huangshan Hot Springs, in central China, where waterfalls and rushing water provide a steady din. The frog has a recessed eardrum, said Albert Feng, a professor of molecular and integrative physiology at the University of Illinois and team leader on the new study.
"In the world we know of only two species -- the other one in southeast Asia -- that have the concave ear," Feng said. "The others all have eardrums on the body surface."
Earlier studies, conducted by Feng, Jun-Xian Shen at the Institute of Biophysics at the Chinese Academy of Sciences and Peter Narins at the University of California, Los Angeles, found that O. tormota males emit -- and respond to -- unusual chirping calls from other males. These calls are audible, but also have energy in the ultrasonic range. The recessed ear structure protects an eardrum that is 1/30 the thickness of that of a normal frog, allowing it to detect very high frequency sounds.
The unusual ear structure and the high-pitched calls are likely an evolutionary adaptation to the noisy environment, Feng said. The waterfalls and streams produce a steady racket predominantly in a lower frequency range than that used by the frogs.
Laboratory experiments showed that the frogs could hear most of the audible and ultrasonic frequencies emitted by other O. tormota frogs. The only other animals known to use ultrasonic communication are bats, dolphins, whales and some insects.
The calls are quite complex. A single O. tormota frog broadcasts its message over several frequencies at once, at harmonic intervals, like a chord strummed simultaneously on several strings.
The new analysis, conducted by Shen, Feng and Narins, found that female O. tormota frogs also emit a call that spans audible and ultrasonic frequencies. The team has not observed females vocalizing in the wild (these frogs are nocturnal and can leap up to 30 times their body length), but in laboratory settings the females emitted calls only when they were carrying eggs.
Male O. tormota frogs exposed to recorded female calls were quite responsive, usually chirping within a small fraction of a second.
"The frog's response is instantaneous -- right after the stimulus," Feng said.
In the laboratory, the males usually chirped and then leapt directly at the source of the female call. Their ability to home in on the sound call was astonishingly precise, Feng said. A typical male could leap toward the sound with an accuracy of over 99 percent.
"This is just unheard of in the frog kingdom," he said.
Only elephants, humans, barn owls and dolphins are known to detect sound with similar precision. The small distance between the frog's ears (about one centimeter) makes its ability to localize the sound that much more impressive, Feng said.
How the female picks a mate in the wild is still unknown, however.
"We have a lot of work to do to figure out whether she directs the signal to one male or whether she lets a bunch of males come and compete, or whether there is any kind of dueting session during which she then decides: 'OK, You're my guy. Hop on my back and I'll take you to the creek!'" Feng said.
These studies likely have implications for human health. Earlier research into the mechanics of frog hearing and directional hearing helped Feng and his colleagues at the U. of I.'s Beckman Institute for Advanced Science and Technology design an "intelligent" hearing aid that boosts sound signals of interest embedded in other sounds in the immediate environment of the listener.

Fausto Intilla - www.oloscience.com

Stressed Seaweed Contributes To Cloudy Coastal Skies, Study Suggests

Source:

http://www.sciencedaily.com/releases/2008/05/080506103036.htm

ScienceDaily (May 7, 2008) — Scientists at The University of Manchester have helped to identify that the presence of large amounts of seaweed in coastal areas can influence the climate.
A new international study has found that large brown seaweeds, when under stress, release large quantities of inorganic iodine into the coastal atmosphere, where it may contribute to cloud formation.
A scientific paper published online May 6 2008 in the Proceedings of the National Academy of Science (PNAS) identifies that iodine is stored in the form of iodide -- single, negatively charged ions.
When this iodide is released it acts as the first known inorganic -- and the most simple -- antioxidant in any living system.
"When kelp experience stress, for example when they are exposed to intense light, desiccation or atmospheric ozone during low tides, they very quickly begin to release large quantities of iodide from stores inside the tissues," explains lead author, Dr Frithjof Küpper from the Scottish Association for Marine Science.
"These ions detoxify ozone and other oxidants that could otherwise damage kelp, and, in the process, produce molecular iodine.
"Our new data provide a biological explanation why we can measure large amounts of iodine oxide and volatile halocarbons in the atmosphere above kelp beds and forests. These chemicals act as condensation nuclei around which clouds may form."
The paper's co-author, Dr Gordon McFiggans, an atmospheric scientist from The University of Manchester's School of Earth, Atmospheric and Environmental Sciences (SEAES) said: "The findings are applicable to any coastal areas where there are extensive kelp beds. In the UK, these are typically place like the Hebrides, Robin Hood's Bay and Anglesey. The kelps need rocky intertidal zones to prosper - sandy beaches aren't very good.
"The increase in the number of cloud condensation nuclei may lead to 'thicker' clouds. These are optically brighter, reflecting more sunlight upwards and allowing less to reach the ground, and last for longer. In such a cloud there are a higher number of small cloud droplets and rainfall is suppressed, compared with clouds of fewer larger droplets.
"The increase in cloud condensation nuclei by kelps could lead to more extensive, longer lasting cloud cover in the coastal region -- a much moodier, typically British coastal skyline."
The research team also found that large amounts of iodide are released from kelp tissues into sea water as a consequence to the oxidative stress during a defence response against pathogen attack. They say kelps therefore play an important role in the global biogeochemical cycle of iodine and in the removal of ozone close to the Earth's surface.
This interdisciplinary and international study -- with contributions from the United Kingdom, the Netherlands, Germany, France, Switzerland, the European Molecular Biology Laboratory (EMBL) and the USA -- comes almost 200 years after the discovery of iodine as a novel element -- in kelp ashes.
Adapted from materials provided by University of Manchester.

Fausto Intilla - www.oloscience.com