To zip through water, swordfish reduce drag
Olympic swimmers shave their bodies before a major race to break records. Swordfish utilize an alternate trap, another study recommends: They oil their heads. The fish (Xiphias gladius) are among the quickest in the sea — their streamlined bodies can slice through the water at around 90 kilometers for each hour.
A newfound oil-creating organ in the fish’s head gives it smooth skin that could support its velocity, researchers report in the July 6 Journal of Experimental Biology. X-ray filters demonstrate that the organ connections to modest pores on the head that overflow the oil, making a meager layer of grease on the skin’s surface.
Little furrowed structures called denticles encompass the pores. Denticles look like scales yet are made of dentine and finish, similar to teeth. The researchers, a group from the Netherlands, think the grease and the textured denticles may cooperate, making a water-repulsing surface that gives swordfish a chance to skim through the water with negligible drag.