Slender body, sharp teeth, big mouth - these characteristics characterize the family of the Barten-Drachenfische. Among them is the subfamily of the shingeless dragonfish (Grammatostomias dentatus), which live in the deep ocean of the Atlantic - and can devour even prey animals of its own size without problems, by tearing their mouth up to 120 degrees. The two researchers Nalani Schnell of the Musée National d'Histoire Naturelle in Paris and David Johnson of the Smithsonian Institution were able to figure out how to do this. The deep-sea fish have a cartilage segment between the occipital bone and the first cervical vertebra. "For most other fish, the first cervical vertebra is directly attached to the head, and there is no flexible joint in between, " explains Nalani Schnell. When the dragonfish open their mouths to catch a prey, they push their jaws forward and head back. The cartilage segment at the back of the head makes it possible, similar to a joint, to open the mouth so far. The researchers discovered the additional cartilage on preserved museum pieces of the scaleless dragonfish. So far, it is the only deep-sea organism where biologists were able to observe the flexible cartilage segment. To the picture: At this Grammatostomias dentatus the bones are colored red and the cartilage parts blue.
Photo: Nalani Schnell, MNHN
- Nalani Schnell, David Johnson, "Evolution of a Functional Head Joint in Deep-Sea Fishes (Stomiidae)", PlosOne Feb. 2017