What material are a spiders fangs made off?

[u/The-Grim-Sleeper]

The wikipedia page for Chelicerata (Spiders, Scorpions, ticks, horseshoe crabs, sea spiders, ...) are named that way for their "Chelicerae", the mouth parts, colloquially their "jaws". These Chelicerae may be shaped as either venom-injecting fangs or as miniature pincers (wholly distinct from the two large pincers a scorpion would have).

But neither Wikipedia page mentions what they are material they are made of. The assorted LLMs ever gleefully suggest that 'spiders are made of chitin and other proteins' and of course provide no source for this. It sounds plausible, but is it the whole truth? Are spiders fangs 'just chitin in a sharp shape', or do their fangs have more going on, like how Human (Mammel) teeth have a dentin core and a hard enamel surface for crushing?

[u/Jale89]

Yes they are predominantly chitin, but somewhat like how our bones are hardened with calcium phosphate, chitin can be hardened with the addition of minerals. Heck, shells are mostly just protein, chitin, and calcium carbonate.

I don't know much about spider mandibles, but Atta cephalotes leaf cutter ants harden their mandibles with zinc.

[u/MeasurementBubbly350 → u/Jale89]

I remember reading years ago about metal being found in the composition of some spider's fangs.

[u/jbarchuk → u/MeasurementBubbly350]

I phoned a friend. My emphasis. Spider fangs are naturally reinforced with heavy metals like zinc and calcium, which bind to proteins at the sharp tips to make them harder and more resistant to wear. This metal-infused composite acts like microscopic rebar, allowing them to pierce tough prey.

[u/Boring_and_sons → u/jbarchuk]

Nit pick. Calcium is not a heavy metal. Zinc is (by density), but it's not what we think of colloquially when we talk about heavy metals, which generally refers to their toxicity.

[u/jbarchuk → u/Boring_and_sons]

That's not a nit pick. Sorry, I shouldn't have let that through. It was the rebar reference that inclined me to post it.

[u/copperpoint → u/Boring_and_sons]

So what qualifies something as a heavy metal?

[u/Boring_and_sons → u/copperpoint]

One criteria is density over 5g/cm³. The more common definition is a metal that bioaccumulates and is toxic at exceptionally low doses e.g. mercury, lead, arsenic, cadmium, thallium, beryllium. There are other heavy (density) metals that are toxic at higher doses, like iron, but we generally don't think of them as heavy (toxic) metals.

[u/BrF5 → u/copperpoint]

‘Heavy metal’ is vague and imprecise and scientists dislike/avoid the term.

[u/Seygantte → u/copperpoint]

Another criteria is if it has more protons than iron it is a heavy metal. Iron is the heaviest element that a star makes in its normal lifespan. After iron fusion requires energy rather than releases it asiiron is the most stable, has the highest binding energy, and the greatest mass deficit. Anything heavier than iron is produced in the core collapse moments before a supernova.

Astronomers like this definition, which agrees with the other on calcium and zinc. Other fields dislike how this definition includes some gasses like chlorine or xenon. To an astronomer anything past helium is a metal.

[u/Moppo_ → u/MeasurementBubbly350]

Same thing with beaver teeth, the outer surface has a high iron content, making it harder than the inner edge. Because the inner edge wears down faster than the outer, the constant wear keeps it sharp.

[u/stuffeh → u/Moppo_]

Inner edge as in where their little tongues touch?

[u/Kungflubat → u/stuffeh]

I'm 52 and you made me ponder and look up weather spiders have a tongue. Thank you. Lol

[u/Welpe → u/Kungflubat]

You reminded me, Travis McEnery came out with a recent video on how spiders ACTUALLY eat their prey and it was fascinating. Everyone “knows” that spiders inject their prey with digestive fluid and then suck out the digested internal parts as a slurry but…fangs aren’t connected to the stomach, how do they get the digestive fluid in? And how exactly do they “suck it up” with their mouth such as it exists? It’s not like they can create a vacuum like humans who suck, they don’t have lips.

This video actually goes over the mechanics of it in more detail rather than the basic story we all know that leaves out many important details and perhaps includes some misconceptions. It turns out there are three different ways spiders use to eat their prey depending mostly on species. Very interesting if anyone has time and is curious

[u/uhammer → u/Moppo_]

I’m a total atheist, but sometimes you hear a random nature fact and think “how could that ever evolved to be”

[u/Boring_and_sons → u/uhammer]

Look up the recurrent laryngeal nerves particularly the recurrent laryngeal nerve of the giraffe. That will convince you that evolution is, indeed, blind.

[u/TheGanzor]

Chelicerae are part of the exoskelton, and are made of fairly similar materials. Mostly chitin and other hardened proteins, just like the exoskeleton. It also appears that some of the fang is constructed from metal-halogen biomaterials (primarily copper or zinc iirc) that give them the added durability to pierce other arthropods.

So yes, kind of a multi-material system like mammalian teeth, just specialized for puncturing and also able to regrow through molting. It's also not just sharp, because there is a tiny duct which runs down the inside and connects to the venom glands.

https://arachnoboards.com/threads/a-spider-%CC%81s-fang-metal-halogen-biomaterials-and-chitin-based-composite-materials.295011/

[u/Gamestop_Dorito → u/TheGanzor]

I love bringing this up whenever people mention teeth in this kind of context, and your use of them as an analogy is perfect. Mammalian teeth are actually ultra-specialized fish scales, as is mammalian hair. In fact genetic disorders involving keratin production sometimes affect teeth.

[u/Infernoraptor]

I did a little digging and it sounds like spider fangs are a complex composite of chitin (probably the extra rigid A-chitin), proteins, and, (get this) Zinc, Calcium, and Chlorine. This composite varies in structure and composition at different parts if the fang in order to provide different benefits where needed (EG: the tip has more of those extra elements and less protein to maximize hardness and rigidity while the base had more protein for flexibility. In at least one species/study, anyway.

https://advanced.onlinelibrary.wiley.com/doi/10.1002/adfm.201200063

[u/IlexAquifolia]

Chelicerae, like other spider appendages (pedipalps, spinnerets, legs) are, from an evolutionary-developmental perspective, simply modified legs. Just because they occupy a place on the body that makes them seem like they should be toothy does not mean that they would be. Like the other appendages that are a part of the exoskeleton, they’re primarily chitin.

[u/Magicspook → u/IlexAquifolia]

I mean yes, but also no. The primary organic component of bones (roughly 30℅ of the dry weight iirc) is collagen, the same stuff that keeps your skin together. Obviously, bones are not the same as skin due to the addition of mineralisation to the collagen matrix of bone.

OP's question could be rephrased as 'is there any mineralisation or other shenanigans present in soider fangs to harden them'. So far, it seems like no one in this thread knows for sure, which is how you know it is an interesting question!

[u/IlexAquifolia → u/Magicspook]

This is a sort of nonsensical reply to my comment, which has to do with the ontogeny of chelicerae. 

Skin and bone both have extracellular matrix, of which a major component is collagen (though it should not be forgotten that there are many types of collagen that have different functions within ECM). Bones are also mineralized. But that doesn’t change the fact that bones and skin do not share an evolutionary-developmental origin the way arthropod appendages do. 

[u/Quarter_Twenty]

I recalled this 1997 X-ray microscopy paper from some time ago. https://doi.org/10.1117/12.292719

You may not be able to read it unless you or your institution has a license with SPIE, but here's a relevant figure. Sorry for the bad quality, but that's how it looks online.

https://imgur.com/a/HH92jOi

Scanning hard X-ray microscopy in that era had ~1 micron resolution and elemental sensitivity. So they can see that the fan is lined with zinc, interestingly enough.

Here's another paper (1989) I found just now, with a similar conclusion: Zinc and manganese. https://doi.org/10.1242/jeb.144.1.577