A belly full of worm

Odontomachus haematodus with parasite. Armenia, Belize.

I can’t imagine what an insect infected with a mermithid nematode must feel. In Belize last week we encountered several parasitized trap-jaw ants, each stumbling about with a belly twice the heft of that in a healthy ant. Scaled to human size, a mermithid would be at least as intrusive as an anaconda coiled among the intestines.

Young worms infect ant larvae via contaminated soil in the brood nest. Adult ants who developed with a parasite sapping their nutrients eclose in a recognizably stunted fashion: a swollen, worm-hosting abdomen and a curiously shrunken head. I was surprised on photographing the victims that the trap-jaw could still snap shut audibly and convincingly.

How affected are mermithized ants? Compare an infected individual to a healthy one (albeit of a different species):

Top: a mermithid-carrying Odontomachus haematodus ant with distorted abdomen and shrunken head; bottom: a healthy Odontomachus clarus worker showing typical proportions for an uninfected ant.

When mature, worms break free from their hosts. The process kills the poor ant, but it frees the nematode to mate and lay eggs.

Still. One more reason I’m glad not to be an insect.



photo details:
Canon MP-E 65mm 1-5x macro lens on a Canon EOS 7D
ISO 200, f/13, 1/100 sec
diffused overhead twin flash

27 thoughts on “A belly full of worm”

    1. Bugsintheattic Mark

      I doubt they “feel” anything like what we think of as feeling…yes they have nerves, but a very segmented nervous system, and given the manner in which they tolerate all forms of damage, parasitism, and dismemberment I do not think it possible they feel in any manner similar to mammalian feelings. But I agree – would not want to be this low on the food chain! Great images and information!

  1. Oh, what nice pictures! I saw something similar when recently got some Tenebrio larvae to feed my ants, and as pets to my son – who reads to them every night in order to keep them strong and smart :). Well, what disappointing it was when while cutting one, I discovered a gigantic nematode inside it (but at least it was funny to make the pet shop owner confused with my approach: “Your mealworms had worms inside”).

  2. That’s definitely one of the more disturbing pictures, but still an amazing shot. Do the nematodes move much? My general animal empathy is kicking with sympathy itches on this one.

  3. I’ve always been bothered by how much these worms look like cellophane noodles. Not because I am repulsed by rice noodles, but because these worms look vaguely edible…

  4. Alexandra Glauerdt

    Very interesting and great photography! Hope you are sharing it in many avenues to publicize how fascinating nature is.

  5. I’ve collected similar nematodes from the abdomens of grasshoppers in North Carolina. Grasshoppers are large insects, and those nematodes were huge!

    1. Maybe what you have seen in grasshoppers are Nematomorpha, horsehair worms, a separate phylum of worms that parasitize in large beetles and grasshoppers. The host organisms finally move to water where the worms crawl out. Here are a couple of pics of such worms:
      http://www.ameisenforum.de/335353-post3.html Photos 4 (habitat in the French Alps), 5 and 6.

  6. Just spectacularly beautiful images. I am intrigued by the wide disparity in nematode prevalence among insect groups. It seems as though every crushed grasshopper I encounter each fall is a virtual “bag o’ worms”, yet nematodes are present in only ca. 1 in 1000 corn rootworm beetles. Certainly the host size differences limit the load (the rootworm rule is one per beetle), but are there some other host characteristics (close association with soil) that predispose species to become nematode hosts?

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  9. Wow. Very cool, but also disgusting photo. I’m into weird stuff, especially stuff like cordyceps (I love the new post!), but parasites are hard for me to stomach (pun intended, ha ha.)

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