Papuan weevil has screw-in legs

July 1, 2011 by Lin Edwards, report
Trigonopterus vandekampi, holotype, habitus. Image: Wikipedia.

( -- New research has found that humans were not the first species to invent the nut and bolt mechanism for screwing one thing to another: weevils do the same to attach their legs to their bodies instead of using the more familiar ball-and-socket joint.

Scientists from the Institute for Synchrotron Radiation at the Karlsruhe Institute of Technology (ANKA) and the State Museum of Natural History in Karlsruhe in Germany, led by Thomas van der Kamp, have been studying Trigonopterus, a genus of 90 described of flightless weevils originating in tropical forest regions of New Guinea, Sumatra, the Philippines, Samoa and New Caledonia. Scientists estimate there could be as many as 1,000 undescribed species in the genus.

Weevils are herbivorous of the Curculionoidea superfamily represented by over 60,000 species found world-wide. The most widely known species are Sitophilus granaries, which is often found in stored grains and other dried foods, and Anthonomus grandis or boll weevil, known for its damage to .

Papuan weevil has screw-in legs
SEM photographs of the right metacoxa (A,B) showing notch (n) and inner thread (i), and of the corresponding trochanter (C,D) with external thread (e) and condyle (c) in Trigonopterus sp. Image: Science/AAAS, DOI:10.1126/science.1204245

Van der Kamp and colleagues studied computed tomography (CT) scans of the Papuan weevil Trigonopterus oblongus and discovered the top section of the weevil’s are attached to the body via the trochanter, which screws into another small body part called the coxa, which is equivalent to a hip. The joint was previously thought to be of a hinge type.

The inside of the coxa and external surface of the trochanter features threads like those found in nuts and bolts. The threads on the trochanters cover around 410 degrees or more than a complete rotation, while the internal threads on the coxa cover 345 degrees.

Nature uses screws and nuts
Weevils are widely distributed and rich in species. The different, partly exquisitely colored species all have a thorn-shaped extension of their head. Credit: Source: Karlsruhe State Museum of Natural History

The muscles turn the legs on the screw threads, an arrangement that allows the weevils to twist their hind and middle legs through 130 degrees, and their front legs through 90 degrees. The joint is more difficult to dislocate than a ball-and-socket joint.

Van der Kamp then examined the legs of 15 more weevil species from different families to see if the same arrangement was used and discovered they did have a nut and bolt system like T. oblongus. The researchers suggested that “it’s a safe bet that all weevils have it.”

Nature uses screws and nuts
Both parts of the weevil’s hip joint fit like screw and nut. This increases the mobility of the leg. Credit: Source: KIT

The T. oblongus lives among leaf litter and twigs, and having a screw-around leg could be useful for helping it to find footholds while searching for food. The arrangement is also likely to give the beetle added stability in its resting posture. It is likely that the earliest weevils also lived among forest leaf litter, which could explain why weevils that no longer live in the same type of habitat have the same mechanism for leg attachment.

The paper was published today in Science.

Explore further: No Mistaking this Bug with New Insect ID Technique

More information: A Biological Screw in a Beetle’s Leg, Science 1 July 2011: Vol. 333 no. 6038 p. 52. DOI:10.1126/science.1204245

The coxa-trochanteral joints on the legs of the weevil Trigonopterus oblongus (Pascoe) work as a biological screw-and-nut system. The apical portions of the coxae closely resemble nuts with well-defined inner threads covering 345°. The corresponding trochanters have perfectly compatible external spiral threads of 410°.

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4.7 / 5 (3) Jul 01, 2011
Interesting. Might be fine for a little beetle, but it might be more likely than a ball-and-socket joint to get jammed in a large animal, and maybe that's why natural selection gave us the ball-and-socket type.
4.2 / 5 (5) Jul 01, 2011
If the legs can 'twist' through so many degrees, I wonder how much they can move in other directions? (Similar to how a worn bolt 'rattles' in a nut. Ie, degrees of tilt away from being coaxial.)
I also wonder if this was an adaptation to keep the legs firmly attached when escaping from predators. Ie, having to yank themselves free.
Or maybe weevils have repair shops where they can go for a quick upgrade. ;-)
4.7 / 5 (3) Jul 01, 2011
Can't wait to hear how the ID crowd calls in on this one. Of course, if the beetle was carrying a spare leg in it's trunk, then all bets are off.
1 / 5 (1) Jul 01, 2011
ID = Intelligent Design?
3.3 / 5 (7) Jul 01, 2011
I think god has also provided Religionists with this screw feature because they tend to have many loose ones.
4.3 / 5 (6) Jul 01, 2011
ID = Intelligent Design?

No, it's Idiotic Design.
1.5 / 5 (6) Jul 02, 2011
ID = Intelligent Design?

No, it's Idiotic Design.

Acronyms Scarcely Suffice (ASS) :)
1 / 5 (12) Jul 02, 2011
I believe that the only thing in this universe that "just so happens" is God: everything beside does appear to have a purpose, a logical function if you will; I have even heard Richard Dawkins say that "if you were to look you may even find what appears to be a sort of design" which he soon after attributes to possible aliens that planted life here on earth, but then follows up with "but even they themselves must have evolved by some kind of darwinian mechanism" (I am quoting by memery here from Ben Stein's "No Intelligence Allowed" so bear with me a moment). The point is that it is OK and still intelligent and just plain obvious that many things, if not all at last, do appear to possess a design, a blueprint if you will that is passed on and yet never appears to be improved upon, in any real sense, in the cares of our observations of them.

I propose that the atheist need not deny that things do appear to be "designed" because they just do;-->>>
1 / 5 (10) Jul 02, 2011
Instead, they should, if they are themselves "intelligent" be able to admit the obvious (that there really does appear to be intelligent design) and at the same time be able to provide a plausible explanation for the phenomenon of intelligent design in the universe.

In more words, denial should not equal a finality of reason in this case!

I believe that purpose can be both a function of design and/or of free will. God, is of course the perfect example of this: not being himself "designed" has he not purposed himself by means of his will? On the other hand, I would not attribute free will to the roots of a plant, and yet their purpose is obvious to anyone who has familiarized themselves with the function in light of the overall scheme of plant life!
1 / 5 (10) Jul 02, 2011
"I believe that the only thing in this universe that "just so happens" is God: everything beside does appear to have a purpose, a logical function if you will;"

To clarify this statement: I should like to add that God's existence is "truly a mystery" all else can be traced back to his activities or allowance. He is the great wonder of this life, and shall be a joy to experiance forever.

Furthermore, and more to clarifying, God is independant of an external source by Biblical definition and therefore doesn't need any excuse for appearing as and being who he is! Us on the lefter hand do appear to be in need of an excuse for our appeareance and being, which seems to only be achievable through an acknowledgement of God's activities and leadership: if God can't tell you who you are and what to make of eternity than who can?

I have sometimes wondered what God's own philosophy of life is. It seems obvious that his affirmation that "I am that I am" means that as their is no cause-->
1 / 5 (10) Jul 02, 2011
For his existence, niether is there any need to justify his existence nor explain why he is the way he is. In other words the essence of God is his independant existence.

Certainly there is intelligent design and the best explanation for it is that God so happens to be an intelligent designer!
3 / 5 (6) Jul 02, 2011
@Argon; please read the "Comments guidelines" (a link can be found just below your "submit" button). It clearly states "Keep science", "Avoid political and religious discussions", and "Keep it short & concise". Your posts are in danger of being removed by the moderator (if people report it as abuse). Also consider this an explanation as to why you've been ranked 1/5.
1.6 / 5 (5) Jul 02, 2011

I acknowledge your post and will consider your recomendations!

As for the rankings, you know full well that I don't control other people nor what they consider "abuse"!

That aside, you are right in regards to posting lengths! I will try to be more brief!
5 / 5 (2) Jul 02, 2011
Certainly there is intelligent design

3 / 5 (8) Jul 02, 2011
Certainly there is intelligent design and the best explanation for it is that God so happens to be an intelligent designer!
And yet he makes significant mistakes doesn't he? Mistakes of the sort that you've been struggling with all your life I bet. The compulsive pathology indicated by your posts is evidence of this.

Per the topic you should curse him for screwing you up like a weevil. Then you should give him up entirely and seek more effective help.

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