Dragonfish opens wide with flex neck joint

Soft tissue at base of skull helps deep sea fish swallow big

stained image of fish head

SAY AHH  Small but ferocious dragonfish (Grammatostomias dentatus shown) can open their mouths wide using a unique joint at the base of their skulls.

N. Schnell/MNHN

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Dragonfish are the stuff of nightmares with their oversized jaws and rows of fanglike teeth. The deep sea creatures may be only several centimeters long, but they can trap and swallow sizable prey. How these tiny terrors manage to open their mouths so wide has puzzled scientists, until now.

In most fish, the skull is fused to the backbone, limiting their gape. But a barbeled dragonfish can pop open its jaw like a Pez dispenser — up to 120 degrees — thanks to a soft tissue joint that connects the fish’s head and spine, researchers report February 1 in PLOS ONE

Nalani Schnell of the National Museum of Natural History in Paris and Dave Johnson of the National Museum of Natural History in Washington, D.C., examined preserved specimens of nine barbeled dragonfish genera. Five had a flexible rod, called a notochord, covered by special connective tissue that bridged their vertebrae and skulls. When Schnell and Johnson opened the mouths of the fish, the connective tissue stretched out. The joint may provide just enough give for dragonfish to swallow whole crustaceans and lanternfish almost as long as they are.

X-ray of dragonfish
BIG GULP This X-ray image reveals that a dragonfish has eaten a large lanternfish in a single gulp. N. Schnell/MNHN

OPEN WIDE  Some species of dragonfish (Eustomias obscurus shown) open their jaws like Pez dispensers, thanks to a flexible joint at the base of their skulls. The joint may allow the fish to swallow bigger prey, which they trap with their fanglike teeth. N. Schnell/MNHN

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