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SKEPTOID BLOG:

Sawfish has Sixth Sense; Does not See Dead People

by Guy McCardle

June 22, 2011

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Donate New research shows for the first time that sawfish have a sixth sense located in their snouts (rostrum) and that they use it to hunt and dismember prey. Scientists previously had thought that the sawfish solely used their saws to dig in mud and sand. The somewhat intimidating saw can also be used as quite a effective weapon whose lateral swipes can cut smaller fish in half.

Barbara Wueringer, a sensory neurobiologist at the University of Queensland in Australia, reports in National Geographic online that the long tooth-lined rostrum is full of pores that detect electrical fields of passing prey. She calls it a sort of a "distant touch". Sharks, rays and some egg laying mammals (such as the spiny anteater and duck billed platypus) also possess these electrorecetpors. In the platypus, this form of electroreception is known as "bill sense".

Wueringer mapped the skin of four species of sawfish, noting the distribution of pores on the saws. She compared this pore placement with the known pore placement on two species of shovelnosed rays. A comparison of pore concentration allowed her to extrapolate clues regarding the animals' feeding behavior. "For example, rays have their eyes on the upper side of their head, but the mouth is on the lower side. Pores that can detect electric fields around the mouth allow these animals to sense a fish when they are trying to ingest it— but cannot see it," she said. In the sawfish, the pores are most concentrated on the upper sides of their rostra, which should enable the predators to stalk fish in the space above their saws.

Research on these fish is important partly because of their alarmingly dwindling numbers. The shallow coastal habitats of these species are often associated with high levels of human activity. As a result, sawfish habitats are severely fragmented. Their numbers have dropped by as much as 90% in recent years. Back in 2003, the smalltooth sawfish was the first U.S. marine fish to be named to the endangered species list. Although it is illegal to do so, sawfish are caught for their prized rostra, teeth and fins which are dried, ground up and sold for "medicinal" purposes. Don't believe everything you hear from the medicine man, however. Drinking soup made from the fin of a sawfish won't let you communicate with the dead.

 

by Guy McCardle

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