Biological screw joint

Alexander Riedel of the State Museum of Natural History Karlsruhe and Thomas van de Kamp of the Karlsruhe Institute of Technology[1] discovered it in specimens of Trigonopterus oblongus, a weevil found in Papua.

[2] Anatomical examination was made for specimens of the weevil species Trigonopterus oblongus, provided by the Karlsruhe State Museum of Natural History, using a microtomograph at the Institute of Synchrotron Radiation (ANKA) of Karlsruhe Institute of Technology.

[4] The coxa, in the case of weevils, resembles a nut, and it has a thread running along its inner surface with an angular span of 345°.

[4] It is rod-shaped with a large external spiral flange, having an angular span of 410°, in excess of a full circle, which functions as a thread.

It is surmised that the development of this feature provided additional flexibility which permitted weevils to improve their climbing abilities, keep steady when at rest, and have stronger leverage for piercing by the snout.

Diagram of the biological screw in the weevil Trigonopterus oblongus
The lateral aspect on thorax of the weevil Trigonopterus oblongus . In this genus , the metanepisternite is absent and the elytron touches the metaventrite (indicated).