Sunday, December 19, 2010
December 19, 2010 : Sawfish
Sawfishes are a family of rays, characterized by a long, toothy snout. Several species can attain sizes up to approximately 7 metres or 23 ft, but the family as a whole is largely unknown and little studied. They are members of the sole living family Pristidae within the order Pristiformes, from the Ancient Greek pristēs (πρίστης) meaning "a sawyer" or "a saw".
They are not to be confused with sawsharks (order Pristiophoriformes), which have a similar appearance.
All species of sawfishes are considered Critically Endangered by the IUCN, and the only legal international trade involves live Pristis microdon to appropriate aquaria for primarily conservation purposes.
The most distinctive feature of a sawfish is the saw-like rostrum. The rostrum is covered with motion- and electro-sensitive pores that allow sawfish to detect movement and even heartbeats of buried prey in the ocean floor as the sawfish hovers over the bottom. It is also used as a digging tool to unearth buried crustaceans. When a suitable prey swims by, the normally lethargic sawfish will spring from the bottom and slash at it with its saw. This generally stuns or injures the prey sufficiently for the sawfish to devour it without much resistance. Sawfish have also been known to defend themselves with their rostrum, against predators such as sharks, and against intruding divers. The "teeth" protruding from the rostrum are not real teeth, but modified tooth-like structures called denticles.