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Research Roundup

08 May 2008

Why endangered parrot population isn’t recovering

The population of wild Puerto Rican parrots, among the most endangered birds in the world, has languished for decades, with several dozen remaining birds unable to break through the bottleneck that prevents their numbers from growing.

A new study by an international team led by Berkeley biologist Steve Beissinger sheds light on the factors influencing the stalled growth of this parrot’s population and, in turn, provides an analytical tool that could help pinpoint the biggest factors hindering the recovery of other endangered species. The research, published in the May issue of the journal Ecological Monographs, not only highlights the various challenges to the parrot’s recovery but identifies the factors hindering population growth.

The model integrated 30 years of data on the Puerto Rican parrot, which was listed as an endangered species in 1967.

After testing the range of hypothesized factors impacting the bird’s struggle to increase its population-growth rate, the researchers found that hurricanes play the largest role in holding back the parrot’s recovery. The next-largest factor is the failure of mature adult birds to mate and breed. Lower-priority factors include the availability of nesting sites and the failure of eggs to hatch once laid.

Puerto Rican officials are trying to establish a second population of wild parrots elsewhere on the island. “This will help act as an insurance measure against further environmental disasters,” says Beissinger. “But without understanding why the existing wild population has grown so slowly, the new population may get stuck in the same bottleneck.”

— Sarah Yang

Glowing sugars light up zebrafish

Using artificial sugar and some clever chemistry, Berkeley researchers have made glow-in-the-dark fish whose internal light comes from the sugar coating on their cells.

This novel method of fluorescently tagging the sugar chains, or carbohydrates, that coat cells is a new tool for those studying development in the zebrafish, a laboratory organism popular because its transparent embryos allow easy observation of living cells as they develop over time.

“Most people think of carbohydrates as food, but the surface of any cell in our body is adorned with a ton of sugars as well as proteins that allow cells to communicate with other cells and invading pathogens,” says graduate student Jeremy Baskin. “People have had for many years the ability to image specific proteins, but not carbohydrates. We have developed for the first time methods for labeling and imaging carbohydrates inside an intact animal.”

An understanding of how, when, and where cells dust themselves with sugar may shed light on how stem cells develop into tissues, as well as turn up markers of disease, such as cancer, or strategies for battling infectious organisms, says first author Scott Laughlin, who, like Baskin, is a graduate student in chemistry.

One big advantage of the technique is that it is non-toxic and can be used to study living cells, whereas other methods of tagging cell-surface carbohydrates cannot be performed on living specimens.

Baskin and Laughlin, together with Carolyn Bertozzi, professor of chemistry and of molecular and cell biology, and developmental geneticist Sharon Amacher, associate professor of molecular and cell biology, reported their results in the May 2 issue of the journal Science.

— Robert Sanders