Does Trilobites Nibble On Their Molt?

[Melissawow]

I got a question.

Is there any evidence from fossilized remains indicating that trilobites could had consume parts of their exoskeleton to replenish the calcium? Crayfish, Crabs and some other arthropods do so. So what do you think?

[FossilDAWG]

I'm not aware of any evidence for that behavior. If it was common, fossils of molts (which can sometimes be recognized by the absence of free cheeks) would be very rare, and such molts or disarticulated sclerites should commonly show characteristic damage on the edges. I've never seen a trilobite fossil, even completely disarticulated bits, that showed evidence of being nibbled at the edges. Decapods (crayfish, crabs) have claws they can use to break pieces off the molt; the job would be harder for trilobites as they did not have large claws. Some insects eat their eggshell after hatching, or eat the molted exoskeleton, but most do not. There are tradeoffs either way. The exoskeleton does have some nutrients, but these are difficult to access as most of the exoskeleton is indigestible chitin (at least in the case of insects); chitin-binding proteins crosslink the chitin in the hardened sclerites, and some amino acids might be recovered there, but not a lot. On the other hand pathogens such as fungal spores may contaminate the exoskeleton surface; in many cases these have to be ingested to infect the arthropod. So consuming the molted exoskeleton poses some risk for a very small nutritional benefit. Whether or not the risk is worth taking will depend on how scarce the nutritional resources are, which will depend on the type and abundance of food available to the animal.

Don