I actually went and looked at some ant pictures before asking. The internet says that ants have a mouth behind the mandibles. But I'm not sure how it works.
@timhutton I think I'm getting confused because mandibles are a sort of mouthpart. But looking a bit more into this, I think that doesn't mean they're part of the mouth, but more like something that assists in the manipulation of food for the mouth.
Have you heard of the 'endless dispute', the popular name for the anthropod head problem? Zoologists have been debating this stuff, including the homology of anthropod appendages, forever.
@simon I love that zoologists had to recategorize everything after DNA sequencing was invented, because some species just looked similar but were actually very different in evolutionary history, or vice versa. (E.g. hippos being a kind of whale.)
I guess the body-part congruence question is the same thing, but harder. We'd need a complete mutation history from one species to another to be sure.
So now I'm wondering if our jaw is congruent to the ant's mandibles. Wow.
Functionally, in humans the fork and knife held in hands are congruent to the mandibles in ants, and they also work from left and right. (Edit: and I think mandible and hand come from the same Latin root 'manus': e.g. 'manual' means done by hand. But I know zero etymology and zero entomology!)
In terms of function the mandibles of ants are their hands. Although, they do use their front legs and antennae to manipulate objects often. (they use their antennae to pack down sand, for example)
But in terms of development I don’t even know if it would be proper to say arthropod limbs are analogous to mammal limbs! We are both bilaterians but beyond being symmetric tubes? We have more in common with starfish and urchins than ants!
@timhutton@simon Which should really make you hairs stand on end as you contemplate the nature of ant cognitive activity— it is absolutely alien and yet — there are parallels— deep parallels: especially in the patterns of social organization.
Ants and humans do agriculture, make wars, take care of each other, and mould our local environment.
I don't think so. But, to be eusocial you must also be social and that's why there are all these similar developments... that have totally different origins.
@futurebird@timhutton Thanks for your thoughts. I'm a beekeeper and I'm going to be looking at the colonies in a whole new light next time I do an inspection.
The one reason I think the limbs are vaguely homologous is that there's a master regulator gene for all kinds of appendages (including limbs and antennae) called distalless, and it's needed to specify appendage outgrowth in mammals and arthropods.
@futurebird
Whaaat? That's amazing, I always assumed antennae were feeling only. How strong are they? Do they have manipulative ends? Like always when I read your posts I now have several more questions.
Most people seem to assume that and that is their primary function. But, I've watched ants use them like we might use the tips of our fingers to nudge and tap soil in particular.
@futurebird@econads@timhutton@simon Similar to how humans will hold a small flashlight with their mouth, or clamp an object they're working on with their legs.
Not the primary use for those parts, but the secondary use is clearly possible and sufficient.
@timhutton@simon@futurebird
I think fusion of both sides of the mandibles is the norm in tetrapods generally, but there are a number of notable exceptions, particularly baleen whales, and snakes, which for somewhat different reasons have a highly stretchy muscle there, which allows the two sides to spread very far apart, and yet be able to pull them back together when needed. Then there's Ornithischians and their predentary bone, but I've run out of room.