OBSERVATORY
Unlocking the Amber
An insect or a plant trapped in amber, the fossilized resin of trees, is a delight to behold. But it can be a nightmare to study.
The amber can be broken open, exposing the surface of the animal or plant, and scanning electron microscopy can be used to reveal surface features. But studying internal structures -- for instance, by cutting a thin cross-section of tissue for viewing in a transmission electron microscope -- is extremely difficult. The ancient tissues tend to crumble to dust. So only fragments have been examined in this way.
Now researchers at the Free University of Berlin have produced complete cross-sections of a twig of swamp cypress that was embedded in Baltic amber 45 million years ago. Their technique, revealed in Proceedings B of the Royal Society, was to use the ancient resin in combination with a modern one to stabilize the tissues.
The researchers left the twig in the amber, allowing them to cut a 1.5-millimeter slice without destroying the plant tissue. They put one end in a drop of a liquid resin called ERL, which was drawn up into the twig tissue by capillary action.
When the ERL hardened, the twig was cut into thin slices for viewing in both light and electron microscopes, revealing the fine structures of cell walls, nuclei and organelles within the cells.
The researchers say these are the oldest and best-preserved internal tissues from amber yet reported. The technique, they add, can probably be used with insects as well.
A Deep-South Dinosaur
It was found in sedimentary deposits, not amber, and in Patagonia, not the Baltic region, but another fossil is making news. It's the remains of a new deinonychosaur, those meat-eating dinosaurs better known as raptors.
The animal, Neuquenraptor argentinus, was about six feet long and had the curved claw, presumably for ripping flesh, that is a distinguishing feature of raptors.
But the most remarkable thing about the find, reported in Nature by scientists from the Argentinian Museum of Natural Sciences and Ohio State, is the location. It's the first Southern Hemisphere raptor -- and since South America split from North America and Asia 90 million years ago, it's an indication that raptors roamed farther and wider than previously thought. The scientists suggest that deinonychosaurs were probably distributed globally at the beginning of the Cretaceous period, about 145 million years ago.
A Niche Organism
The cyanobacteria are a curious bunch, and among them one species, Acaryochloris marina, is curiouser still. It is the only known photosynthesizing organism that uses the d variant of chlorophyll as its principal means of capturing energy from light. Chlorophyll a is the main photosynthesizing pigment in most other plants and algae.
Chlorophyll d uses light at near-infrared rather than visible frequencies. So one lingering question about A. marina, which was discovered a decade ago in the tropical Pacific, has been where it lives and how it can thrive, given its odd light requirements.
Dr. Michael Kühl of the University of Copenhagen and colleagues have solved the mystery. A. marina, they report in Nature, lives in the shade.
One clue to their discovery was that A. marina was first isolated from extracts of small invertebrates that encrust coral reefs. These invertebrates, called didemnid ascidians, are known to contain other cyanobacteria in symbiotic relationships, so the researchers examined the ascidians to see whether A. marina was living inside them as well.
They didn't find A. marina-type organisms inside, but rather outside, in a thin biofilm. What's more, this thin film was only on the ascidians' underside. Analysis of the ascidian tissue showed that it strongly attenuated visible light but allowed near-infrared light to pass through.
So A. marina, the researchers say, has found a remarkable niche, growing in biofilms underneath another organism that acts as a light filter, allowing A. marina to make efficient use of its unique light-harvesting process.
What's Good for the Grouse
Populations rise and fall all the time, but when separate populations of the same species rise and fall in unison in a region, ecologists really become intrigued. It's long been proposed that weather and climate play a role, but the underlying mechanisms have been hard to determine.
Now, Dr. Isabella M. Cattadori and colleagues have shown that there is, indeed, something about the weather that synchronizes populations of red grouse in northern England. But they've also demonstrated that the effect is an indirect one, with a third party -- an intestinal parasite -- involved.
Dr. Cattadori, now a postdoctoral researcher at Penn State, studied the red grouse while on a fellowship in Scotland. Game birds like grouse are convenient to study in Britain because large hunting estates have kept long-term records to estimate populations.
The researchers collected data from about 100 estates in northern England that showed similar annual fluctuations in numbers. 'Even though the estates are managed independently, their shot data had the same sort of patterns,' she said. 'So there had to be something intrinsic in the populations.'
Dr. Cattadori then examined the populations and the climate. 'We found that the climatic data were very well in synchrony during summer but not winter,' she said. 'So summer was probably more important than winter in affecting the populations.'
Breeding occurs in summer, and red grouse are known to be infected by a worm that affects fertility. So Dr. Cattadori built models to compare two hypotheses: that the weather affected grouse numbers directly, or that it affected the parasite populations, which in turn affected the birds.
Each model fit the data well, Dr. Cattadori said, but the one using only climate wasn't biologically correct. 'It showed that if it rains a lot, it's good for the grouse,' she said. 'We know that's not true.'
But the parasite model made sense. It showed that a dry, warm spring followed by a cold, wet summer kills worms, while a wet spring followed by a warm summer produces lots of worms.
Dr. Cattadori said the work, published in Nature, carries a bigger potential message, about climate change and events like emerging diseases and pest outbreaks. 'We may find that these phenomenon are caused by climate and taking place in a synchronized way,' she said.
Observatory