Saw-wielding fish dismembers its prey!

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A recent study has found that saw of a sawfish is a versatile tool that can be used to locate and dismember prey.

Barbara Wueringer and co-authors studied the predatory behaviour of the Largetooth sawfish (Pristis microdon).

Publishing their results in the most recent issue of the journal Current Biology, the authors studied the behaviour of freshly captured juvenile sawfish when fed with pieces of mullet or tuna.

It is commonly believed that sawfish use their saw to rake through the substrate in search of bottom-living prey, but the authors showed that the saw is a much more impressive weapon than that.

The sawfish studied used their saws to impale and dismember their prey, as well as to pin them against the substrate before eating them. By vigorously swinging their saws from side to side, the sawfish were capable of splitting fish in half.

Previous research has also indicated that the saw is packed with thousands of tiny pore-like organs that can detect the minute electric fields surrounding living organisms and that sawfish have much more concentrated collections of pores on the upper side of the saw than their relatives the shovel-nosed rays.

This indicates that they use their saw to detect prey in the three-dimensional space above the saw. The authors mimicked the weak electrical fields of live prey in this study and confirmed the sensory capabilities of the saw.

"Now we know that sawfish are not sluggish bottom dwellers as previously believed, but agile hunters that hunt in the three-dimensional space of the water," Wueringer said.

As sawfishes are frequently unintentionally caught by entangling themselves in fishing nets (perhaps as a result of trying to eat fish already caught in the net), she added that this understanding of sawfish biology may help to conserve them by restricting the fishing methods allowed in areas where sawfish live.

For more information, see the paper: Wueringer, BE, L Jr Squire, SM Kajiura, NS Hart and SP Collin (2012) The function of the sawfish's saw. Current Biology 22, pp. R150–R151.

See also: Wueringer, BE, SC Peverell, J Seymour, L Jr Squire, SM Kajiura and SP Collin (2011) Sensory systems in sawfishes. 1. The ampullae of Lorenzini. Brain, Behavior and Evolution 78, pp. 139–149.

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