To zip through water, swordfish reduce drag

Newly found organ excretes oil that may increase swimming efficiency


SEA SPEED  Swordfish are one of the fastest fish in the ocean, thanks to their streamlined bodies — and possibly their slick skin.

Angel Fitor/Science Source

Olympic swimmers shave their bodies before a big race to break records. Swordfish use a different trick, a new study suggests: They grease their heads. The fish (Xiphias gladius) are among the fastest in the ocean — their streamlined bodies can cut through the water at about 90 kilometers per hour.

A newly discovered oil-producing organ in the fish’s head gives it slick skin that could boost its speed, scientists report in the July 6 Journal of Experimental Biology. MRI scans show that the organ links to tiny pores on the head that ooze the oil, creating a thin layer of lubrication on the skin’s surface.

Tiny ridged structures called denticles surround the pores. Denticles look like scales but are made of dentine and enamel, like teeth. The scientists, a team from the Netherlands, think the lubrication and the textured denticles might work together, making a water-repelling surface that lets swordfish glide through the water with minimal drag. 

OIL RESERVE An MRI scan reveals that a swordfish has an oil-producing organ (outlined in black) tucked just behind its rapier-like bill. J.J. Videler et al/Journal of Experimental Biology 2016

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