Not So Rapid Eye Movement
The bizarre metamorphosis that occurs in halibut and other flatfish had even Charles Darwin floundering for an explanation. At birth, these fish have one eye on each side of the skull, but as adults, both eyes reside on the same side. Certainly, for fish that spend their lives along the sea bottom, having both eyes topside confers a survival advantage. But there seemed to be no evolutionary reason to start down the gradual path toward such lopsidedness—any intermediate steps would not seem to be especially helpful. So some biologists theorized that the fish evolved from a single, sudden mutation.
That does not seem to be the case: Matt Friedman of the Field Museum in Chicago reports finding some missing links. He investigated two roughly 50-million-year-old primitive flatfish fossils hidden in museums in Europe for more than a century. These adult specimens possessed somewhat asymmetrical skulls that nonetheless kept eyes on opposite sides of the head. Even incomplete lopsidedness may have given the carnivorous bottom dwellers a better view of the world above than no asymmetry at all, Friedman conjectures. Eye the study in the July 10 Nature. —Charles Q. Choi
As parents have long known, children in day care centers and schools readily spread respiratory diseases among one another. Chimpanzee communities seem to suffer in a similar way: playdates drive the dissemination of respiratory infections among the primates, according to a new study.
Scientists led by Hjalmar Kuehl and Peter Walsh of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, examined two chimpanzee groups in Taï National Park in Ivory Coast. Infants were more likely to die from a respiratory disease the more they played together—typically during the peak fruit season, when chimps congregate. Between the ages of two and three, chimps spend up to 18 percent of their day engaged in close physical contact with their peers. This period represents the peak of their social interaction and serves to connect all members of their community.
Once playful chimpanzees precipitated an outbreak, infants of all ages succumbed to disease. Affected mothers quickly entered into estrus, ultimately perpetuating the three-year cycle of infant population boom and bust. Coupled with poaching, climate change and predation, infant mortality from infectious disease is taking
a toll on the area’s chimps, says Kuehl, whose research findings appear in the June 18 PLoS ONE. These days few infants reach adulthood, he states, with “only four out of 10 surviving to the age of five.” —Barbara Juncosa
Another Gene for Alzheimer’s
A newly identified genetic mutation increases the risk for the most common form of Alzheimer’s disease—the second major gene to be linked to the neurodegenerative disorder. The mutation occurs in the so-called CALHM1 gene, which controls calcium concentrations in nerve cells. Researchers observed that mutant CALHM1 led to increased accumulation of amyloid beta plaques, the sticky protein clumps characteristic of the disease. In the U.S.
Alzheimer’s affects one in 20 adults aged 65 to 74; carrying one defective copy of CALHM1 escalates the risk to one in 14 (and to one in 10 for those carrying two defective copies). The mutation also leads to an earlier age of onset. Reporting in the June 27 Cell, lead author Philippe Marambaud of the Feinstein Institute for Medical Research in Manhasset, N.Y., states that the CALHM1 gene—along with the first Alzheimer’s gene, APOE, discovered 15 years ago—will be important in screening for the disease. —Barbara Juncosa