New worlds: Fish get half their nutrition from slimy rocks

The Amnunit Yosef fish swallows pebbles because it gets a great deal of nutrition from their coating.

By JUDY SIEGEL-ITZKOVICH
fish 88 (photo credit: )
fish 88
(photo credit: )
A pebble-eating fish in the Kinneret and a whale species not previously seen in the Mediterranean were mentioned at a recent conference on marine research at the University of Haifa. Prof. Menahem Goren and Yifat Gueta of Tel Aviv University revealed that they discovered that a fish called Amnunit yosef that has a large number of pebbles in its gut does not swallow them by mistake, but because it gets a great deal of nutrition from the coating on the little rocks. The fish, which lives in the Kinneret and Nahal Hakibbutzim, was thought to swallow the pebbles to help it digest food, like a chicken. But the TAU team burned the stones to find out if they contained any caloric value. It turned out that the organic material on the surface comprises about half the nutrition in the fish's diet. Meanwhile, Dr. Oz Gofman and colleagues from the marine civilizations department at the University of Haifa collected data on a new species of whale called the broad-toothed killer. The team studied bodies of the whale that were washed up on the coast and monitored live ones in the Mediterranean. Another species unknown to the region that they observed was a hunchbacked dolphin called Indo-Pacific that was viewed for 10 days while swimming between Atlit and Ashdod. "This is the only documented species of a marine mammal that travels from the Red Sea to the Mediterranean Sea," said Gofman. "Even though the eastern Mediterranean waters are poor in nutrients such as plankton and plants, they have enough to support a variety of species that also live in the western Mediterranean." IDENTIFYING DNA DAMAGE For the first time anywhere, researchers at the Hebrew University-Hadassah Medical School in Jerusalem have succeeded in observing and describing how damaged DNA is naturally identified. The research, which appeared in a recent issue of Cell, sheds new light on understanding this molecular mechanism and is likely to aid in research on diseases involving DNA damage, including cancer. The researchers, headed by Dr. Sigal Ben-Yehuda of the medical school's department of molecular biology, revealed a new protein which scans DNA at the onset of bacterial sporulation. The protein moves quickly along the chromosome and identifies DNA damage. When the protein identifies such damage, it halts at that spot and signals to other proteins which repair DNA. Under conditions of stress, some bacteria undergo a process of division which produces spores. These spores are particularly resistant to heat, radiation, dryness and exposure to chemicals, making it difficult to eradicate them with conventional methods. Most of the knowledge about sporulation of bacteria has been gathered over the years on a bacterium known as Bacillus subtilis that does not cause any illnesses. When this bacterium enters the sporulation phase, it verifies that the DNA sequence is in proper order and does not contain any mutations. But how this occurs has not been observed until now. "It is now possible to see how this phenomenon occurs," said Ben-Yehuda. "Proteins triggered by the bacteria that are similar to the protein revealed in our lab are found in all species, including humans, and therefore one can conclude that the way in which the bacterial protein scans the DNA for lesions is similar among many forms of life. This understanding of the molecular basis of DNA repair is a basic step in furthering our ability to understand those illnesses stemming from DNA damage."