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There are numerous popular articles claiming that the wasp Apocrypta Westwoodi Grandi features an ovipositor tipped with zinc. You can find such an article here. You can watch an impressive video here. Beyond that, I have found information on the genus to be sparse.

Yet my question is, how metallic tissue can be formed. The popular article claims actual zinc was detected. It seems unlikely to me, these creatures consistently find a source of zinc to feed from, so as to deposit zinc in their tissue. Even so, I don't understand how this zinc can be made to deposit at a specific point. The article clarifies:

With an x-ray detector and the electron microscope, they discovered the presence of zinc. It was only on the tips of the parasitic fig wasp’s ovipositors. Gundiah said, “We see it very consistently only at the tip and not anywhere else.”

I am no biologist, but, to my feeble understanding the only alternative is that the so called zinc is actually synthesised by the body as a protein normally is. Surely no atomic reactions could take place in the wasp! :-p Even teeth are mostly Ca5(PO4)3 OH, Calcium is found in plenty of our foods. Phosphorus is present in meats. But zinc? I totally don't understand it!

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    $\begingroup$ I'm not aware of body synthesising ions de-novo. $\endgroup$ – Tyto alba Jun 15 '17 at 11:20
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    $\begingroup$ I don't know about non-trace amounts of zinc but iron is common, and Iron reinforced tissues exists, things like beaver teeth and scaly foot snail shells which are made of iron reinforced enamel and iron sulfide respectively. $\endgroup$ – John Jun 15 '17 at 14:54
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    $\begingroup$ @Ludi You may not be aware but zinc is an essential mineral for all plants and animals (not certain about all bacteria), as are several other metal ions. $\endgroup$ – Bryan Krause Jun 15 '17 at 15:45
  • $\begingroup$ @BryanKrause exactly. Of this I wasn't aware. Now, due to Gillian's answer, I did some research. Before I thought it was extremely rare. Embarrassing, since I was a physicist, but what can I say... $\endgroup$ – Ludi Jun 15 '17 at 16:18
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First and foremost, it looks like the original article is slightly less dramatic:

Parasitoid ovipositor tips have a higher content of the transition metal zinc compared with the cuticle elsewhere on the ovipositor

So a 'higher concentration' isn't quite the same as 'tipped with'. It looks like they are describing a higher numbers of metal ions, rather than pure metal:

The presence of transition metals in insect cuticle and mandible is hypothesized to increase material hardness to permit cutting through hard substrates with minimal wear

There are many examples of organisms using inorganic chemistry to make materials. The overall topic is called biomineralization and you even mention teeth - which is hydroxyapatite (not really organic chemistry!).

However, a pure metal like zinc is unusual, I think. There are examples such as the snail that has an iron pyrite 'armor' or even the iron nanocrystals in ferritin.

More spectacular examples include the bacteria that produce gold particles

As a result, Au detoxification is mediated by a combination of efflux, reduction, and possibly methylation of Au-complexes, leading to the formation of Au(I)-C-compounds and nanoparticulate Au0.

Where Au0 is pure gold. I don't know of any other examples of pure zinc in organisms, but there is a nice review here of zinc biochemistry.

When you say 'synthesise' I assume that you mean 'deposit'.

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  • $\begingroup$ I am not a biologist or chemist so my (faulty?) understanding is that the wasp has to eat zinc to deposit it. Otherwise it has to somehow produce it, which I cannot imagine. My other assumption was that substances based carbon are called organic, with some historically motivated exceptions. $\endgroup$ – Ludi Jun 15 '17 at 13:03
  • $\begingroup$ @Ludi - Sure, they certainly have to eat it, as organisms are not known to synthesise elements! You are right that most compounds with carbon in them are 'organic', but "Ca5(PO4)3 OH" is a calcium compound, with no carbon. $\endgroup$ – gilleain Jun 15 '17 at 13:07
  • $\begingroup$ @gillean oh, gosh, what a stupid mistake! Anyway, it is clear we can get Calcium and Phosphorus from some foods. But where the heck would a wasp get Zinc? $\endgroup$ – Ludi Jun 15 '17 at 13:10
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    $\begingroup$ @Ludi Most foods will have small amounts of elements that we tend to think of as rare - zinc, molybdenum, iodine, etc. It's actually quite common to find zinc in biochemistry, as they are used in a "zinc finger" that binds to DNA - of course, that's just a single atom $\endgroup$ – gilleain Jun 15 '17 at 13:14
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    $\begingroup$ @Ludi: Just to make things clear: the wasp only needs to consume some substance that contains zinc atoms, not actual bits of metal, right? So the molecule containing a zinc atom doesn't need to behave like pure or even concentrated metal at all. From the Wiki article on Zinc Compounds: A very large number of metallo-enzymes contain zinc(II). Also many proteins contain zinc for structural reasons. $\endgroup$ – Cerberus Jun 15 '17 at 21:08

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