This little nematode (Phylum Nematoda) belongs to class Enoplia alongside whipworms and the ever-awesome Trichinella spiralis. M. neotropicum belongs in the order Mermithida, which has members that are mostly arthropod parasites. All members of this order have a stichosome. There are two families within this order. The family that M. neotropicum belongs to is the family Tetradonematidae.
This parasite has an interesting life cycle that begins with a frugivorus (fruit-eating) bird ingesting an infected ant of the species Cephalotes atratus. After going through the bird's gut, the parasite eggs are passed out of the birth through defecation. The bird feces are gathered by worker ants of the aforementioned species, and then fed to the ant larvae. Once inside of the immature ant gut, the parasites hatch from their eggs and migrate to the gaster of the ant, where the parasites mature. Female nematodes are larger than the males in this species.
About the time that the ant larvae pupate, the now-mature nematodes begin to mate inside of the gaster. The males die shortly after copulating and the females begin to develop eggs within their bodies. After the ant matures into a young adult, the embryos within the eggs somehow turn the ant gaster translucent, which allows the red-colored embryos to shine through. The longer the ant is infected, the more red the abdomen becomes.
The parasites also induce a behavioral change. The infected ants carry their abdomens up high in an awkward, unnatural position. The infected ants also move much slower than their healthy brethren. It has been noted that the infected ants begin to forage outside of the nest rather than tending brood within the nest itself as uninfected ants do.
These behavioral changes coupled with the reddening of the abdomen are an example of what has come to be known as "fruit mimicry", because the ant becomes reminiscent of small red berries. Our frugivorus bird friends then mistakenly eat the fruit-mimicking antes and the life cycle of the parasite is completed.
Moral of the Story
This parasite is obviously no threat to us humans, but it is interesting! In fact, I find it more interesting to think of the chain of events that led to this amazing adaptive strategy! THIS is one of the many reasons why parasite evolution is so COOL! :) An now, for your viewing pleasure, a couple of ant pictures. The first is a comparison of an uninfected ant and its infected brother. The second depicts an infected ant alongside some of the berries that are mimicked because of Myrmeconema neotropicum. Enjoy!