MICHELLEHAYWOOD
Sympathy for the slimer
Michelle Haywood meets the hagfish , a creature out of a horror film that might just revolutionise tendon surgery and manufacturing industries
Let ’ s talk Hags . Well , Hagfish to be
precise . In terms of their shape , they look like eels , but they lack spines ( and jaws ). Their pink-grey skin is loosely attached to the underlying tissues , which help it to avoid damage when attacked by a predator . As a shark bites down on a hagfish , the internal bits slide out of the way . It ’ s been estimated that you could add an extra 40 % of body volume to a hagfish without stretching the skin . This makes the hagfish very hard to bite but it has another trick in its repertoire ... slime . Lots of slime . Hagfish readily release copious amounts of slime seconds after they have been attacked . Remarkably , it only takes 0.04 grammes of mucus and protein to make a litre of slime . The slime is considerably softer than jelly . In fact , it almost looks like water until you put your hand in it . The protein threads form an effective mesh that traps water and mucus . The protein threads give the slime its elasticity , the mucus makes it viscous . The hagfish has found a way of using very little material to trap large volumes of seawater in gooey mess that is hard to escape . This slime covers the gills of predators , impairing water flow and risking hypoxia . Most predators will learn to avoid them . There are about 100 slime glands along the side of the hagfish . When provoked , these glands expel cells containing protein threads . Each thread is about 1 / 100th the width of a human hair and about 10-15cm long . These protein threads are cleverly coiled into the cytoplasm of the cell , using the nucleus of the cell as a spindle . All the protein threads within a cell twist in the same direction to prevent tangling , and there is a water-soluble protein that hold the twists of threads in place . The protein threads readily unravel when the cells are ejected into the seawater from the slime glands and rupture . The unravelling process is quick , but works even faster if the end of the protein molecule snags onto something , such as another thread or a predator . If hagfish can release such huge volumes of slime , there ’ s a real risk that they too will become entangled in their own slime . To overcome this issue , hagfish can self-clean by tying themselves in a knot . They twist their heads into a knot around their body and then slide the knot along their body to wipe the slime off . How cool is that ? And the strangeness doesn ’ t stop there . Hagfish have no jaws , but feed by rasping at carcasses using the toothy cartilage in their mouths . And the self-knotting ability helps with feeding too . Once they have latched onto the carcass , they use the knot to leverage out the mouthful of meat . Even stranger still , they can absorb nutrients directly through their skin and gills . It ’ s thought that their skin is more effective at absorption than their intestine . The Hagfish really is just a swimming gut that can sit inside a dead body and absorb nutrients . For divers the most likely place to encounter hagfish is South Korea , where they are considered a delicacy , marinated in sauce and barbequed . They are generally a deep ( about 1,800 metres ), cold water species that like soft seabeds that they can burrow into . You ’ re not likely to encounter one under Swanage Pier . These ancient animals may have lots to teach science , indeed their slime may have a useful future . Farming them is difficult , requires lots of cold water and wouldn ’ t be financially viable . But learning how to make artificial hagfish fibres is already underway . You see , these fibres are stronger than spider silk and more flexible . Making artificial spider silk requires some harsh solvents but hagfish proteins need water only . Incorporating these fibres into composites may replace the Kevlar in bulletproof vests and safety equipment , or add strength to materials like car parts without adding weight . They are even being explored as a way of making artificial tendon replacements for surgery . Who knew that an archaic , spineless , swimming gut could be so intriguing ? �
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