Do insects heal?

So I’m sitting at the bus stop a couple of days ago, and I feel a tickle on my foot (exposed in a Birkenstock sandal). Reflexively, I lean down and brush at the tickle; this swipes an ant off onto the ground. The ant starts to scurry away, but is obviously running with effort. When I look more closely, I see that one of its (her?) legs is messed up, presumably as a result of my brushing action.

I consider stepping on the ant, as I don’t imagine there’s a lot of room in a bug-eat-bug world for a crippled competitor. But as I watch, the ant’s gait smooths out a bit, and it picks up speed; apparently it’s “figured out” how to run on its bum leg, at least well enough to escape immediate danger. So I let it go.

Many thoughts followed, and, ultimately, this thread.

The basic question: How widespread, and effective, are healing faculties in more primitive critters?

I know as a pet owner that cats will go to great lengths to hide their distress, because they don’t want to appear weak and make themselves targets for predation (or of stronger cats). However, given time and rest, they will eventually recover from illnesses and wounds. Further down the scale of primitiveness, starfish can grow a new leg, and crustaceans, new claws. Trees will pitch over a gouge, and eventually fill it in, but usually there’s a scar. And so on.

(By the way, I know that “primitive” isn’t a strictly meaningful term, and can’t be measured on a linear scale. Organisms are either adapted for their niches, or they aren’t; one can’t really say, between a lemur and an osprey, which is “more advanced.” Still, I think there’s a useful lay perception ranking exoskeletal animals beneath reptiles, and mammals above both. So go with the informal sense of the term.)

It seems to me that in the world of the ant, if you lose a leg or an antenna, you just plain aren’t much good to the hive. Not only can you not contribute as much to the hive as an intact ant, you’re also slower and less able to react, which makes you more likely to get et by a bird or a spider or whatever. If ant lives are cheap, damaged ants are worth even less.

So in that kind of world, wouldn’t natural selection gradually whittle down the organism’s capacity to recover from injury? If the ability to heal offers no real survival advantage, and if the energy necessary to build the biological tools necessary to heal would therefore be better spent in areas more likely to do the organism some practical good, doesn’t it make sense that natural selection would tend to sacrifice the former for the latter? If that’s true, for which types of organisms would it apply? Ants and flies? Bacteria? At what level of development does the ability to heal become meaningful?

Or, in short: Should I have stomped the ant? :slight_smile:

(By the way: I searched the archives, and I did try to google this question, but I didn’t find much in the way of illumination.)

Well biologically there is no reason to believe things like healing and immune system are more primitive in cats than in humans. In fact, I’m pretty sure humans suck at healing certain types of injuries much more than other mammals. As for insects, I don’t know

Just off the top of my head I would think that most smaller insects, like ants, live in large enough social groups that a high mortality rate wouldn’t be as damaging to the overall survival of the species as it would be to say a herd of elephants ,so perhaps healing wouldn’t occur since it wouldn’t be beneficial.

With other insects having short “adult” lifespans where most of the effort is given to reproduction and little else I’d be inclined to think not. Also wounded insects would quickly become food given the high number of things out there that eat insects.

One nifty thing about ants is that they cycle through different jobs in the colony. When they’re younger, they do more stuff in the colony itself, but as they get older (and near the end of their lifespan), they start doing more foraging and defending of the colony. So you can rest easy in that if you did happen to fatally injure the ant, she was probably near the end of her life, anyway.

Do insects heal?

This one might: http://boards.straightdope.com/sdmb/showthread.php?t=379268

Insect Immune Suppression

Anyone know SDSTAFF Doug? He seems to have the Straight Dope on ants.

I thought insects could only regenerate lost body parts by molting, the way crabs can regrow a lost claw the next time they molt. Am I way off base?

This is basically correct. Arthropods in general can only regenerate a lost appendage when they molt. Since an ant has completed all of its molts (they undergo molts in the larval and pupal stages, but not once they have molted out of the pupal to take on the adult form) it would be unable to regenerate a limb or undertake any major repair. Insects are, however, able to heal wounds in cuticle to some extent.

Here’s a bit about wound healing in insects

Excellent, thank you.

I gather from this article that this question has yet to be adequately explored. While some things are known, the actual mechanics of healing are so complex that a basic technical foundation needs to be laid before broader conclusions can be drawn.

Some bits, though, are interesting:

In general, then, the biological machinery is in place to handle healing across a variety of organisms. But one of my original questions (picked up by Cluricaun) therefore remains: Why would this potential facility be retained, with its attendant cost of manufacture, if it’s unlikely to do the organism much good?

I don’t see why it’s unlikely to do an insect any good. It certainly seems plausible that an insect could suffer enough minor wounds to make having a repair mechanism worthwhile. Chitin is relatively tougher than most mammal skin, but can still get abraded or punctured.

Also I think that “insect” may be too broad of a spectrum to narrow this down well. I was focused on the OP’s example of ants, which would be difficult to study the healing properties of ants since they will commonly turn on dead or injured members of the colony as a food source (I’m assuming they’re eating them and not carrying them back to the nest for funeral services or thorax rubs) long before any “healing” could take place. Since an evolutionary benefit exists to the ants becoming food, there would be little benefit to healing properties, so I would be surprised if it took place on any large scale, six cellular width needles notwithstanding.

Larger, solitary insects may prove to be much different, such as a tarantula regenerating a limb during a molt.

Particularly as a tarantula isn’t an insect.

Sorry, sorry! Somebody had to do it.

No, totally fair shot. I was caught up in the moment and wasn’t thinking clearly. I was just going for “big solitary bug” and my brain ralphed up “tarantula”. :smack:

Let’s change that to the splendor beetle, which according to a quick Google search is the longest lived insect.

From the point of view of natural selection, it depends entirely on what the reproductive potential of the organism is over the (expected) remainder of its life if it does heal. Note that the article I linked to concerns healing in larval insects. Since larvae won’t be able to reproduce at all unless they make it to the adult stage, obviously wound healing will be at a premium for them, and will be strongly selected for.

I don’t know offhand how much healing ability adult insects retain. In many, perhaps most, insects, the organism spends a far larger part of its life span in the larval stage than as an adult. Many adult forms live only a few weeks, sometimes only days, after emerging from the pupa. For a mayfly with an adult life span of a few hours, clearly there is is little need for a healing mechanism, since it wouldn’t have time to heal before it died naturally anyway. Worker ants, which don’t breed at all, also may not require much of a healing mechanism (although the survival of an individual could be of benefit to the colony). On the other hand, queen ants can live and continue to lay eggs for decades, so healing could easily be selected for in them.

It is also possible that if a healing mechanism is selected for at some stages of the life span, such as larvae, it could also be retained in the adult simply because there is little selective pressure to eliminate it.

Reminds me of this cartoon I saw once: One mayfly is interviewing another for a job openning and asks: So, where do you see yourself in 5 minutes? :smiley: