The scientists placed special equipment on the sharks to direct odors directly to their nostrils. The smells were from squids -- a favorite meal of the smooth dogfish shark.
Then the scientists watched and recorded which way the sharks turned to follow the odor.
Ms. Gardiner said the delay between the arrival of the smell at each nostril could be as little as a half second or less. The animals turned and swam in the direction of the nostril that first received the odor. Ms. Gardiner said this was true even if the odor in the second nostril was stronger.
Following the odor received by the first nostril guided the sharks into smelly areas in the water. The fish then followed the odors to the squid.
FAITH LAPIDUS: The findings also led the researchers to consider why some sharks have strangely shaped heads. The hammerhead shark family is a good example. The name hammerhead describes the animal’s wide, flat head. One theory is that the shape developed over the ages to improve this shark’s sense of smell.
When hammerheads swim into clouds of odor, they usually do not swim straight on. Instead, their bodies are on an angle.
BOB DOUGHTY: Hammerhead sharks have nostrils that are more widely spaced than those of sharks with pointed noses. The placement creates a longer delay between the time the left and right nostrils receive an odor than in sharks with pointed noses.
This suggests that animals with more widely spaced nostrils could attack from better positions while swimming fast. Ms. Gardiner believes this ability may have helped the development of hammerhead sharks over the ages.
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25