Endosymbiosis Among 'Advanced' Organisms

[whc.03grady]

The phenomena of endosymbiosis is probably the most mind-blowing thing I ever found out about in biology.

This question is likely pretty stupid, but could it happen to organisms ‘further’ along (I know evolution’s not a ladder, I just don’t know how else to put it)? I’m thinking about something like caterpillars and moths/butterflies: could it be that caterpillars and butterflies were once independent organisms that somehow got themselves together for their mutual benefit?

[jimbuff314]

You picked what is probably not a good example. Wikipedia entry on butterfly notes that the larvae (caterpillar) already have tiny wing pads internally on the second and third thoracic segments. These are what will expand enormously in the final caterpillar molt upon entering the pupae stage, develop trachea which in turn will become the wing veins. Given that these wing pads are already present during the larval stage, it seems unlikely that these were once separate organisms. Some creatures just grow and develop much, much differently than we do.

[Senegoid]

FWIW, the metamorphosis of a caterpillar into a butterfly is covered in some detail in two reports by SDSABer Doug:

How exactly does a caterpillar morph into a butterfly?, September 16, 2008

OK — WHY exactly does a caterpillar morph into a butterfly?, December 9, 2008

[Ruken]

I think I understand what the OP is asking. The tricky thing is with reproduction. If the organism reproduces with gammettes, would the endosymbiosed (?) organism have to be in one of the gammettes? E.g for us, mitochondria are transferred from one parent to S1 via the egg.

I was reading an article a few months back about how the line between endosymbiosis and symbiosis is fuzzy. That’s probably a good starting point. I’ll see if I can dig it up.

[Ruken]

@Ruken

I was reading an article a few months back about how the line between endosymbiosis and symbiosis is fuzzy. That’s probably a good starting point. I’ll see if I can dig it up.

Science 31 October 2014:
Vol. 346 no. 6209 pp. 532-533
DOI: 10.1126/science.346.6209.532

Those momentous events, investigators are realizing, were not one-of-a-kind. Endosymbiosis, as a mutually beneficial relationship between an organism and a guest living inside its cells is called, is alive and well today, and has lessons to offer for how the process played out early in life history. “The line separating endosymbiont from organelle is very unclear indeed,” said John McCutcheon, a biologist at the University of Montana, Missoula, earlier this month at “Symbioses becoming permanent,” a meeting held here by the National Academy of Sciences and the Canadian Institute for Advanced Research.

At the meeting, biologists described how they are exploring those parallels. They are probing how insects such as cicadas and other multicellular organisms set up partnerships inside their cells with microbes that, like their ancient forerunners that became organelles, help provide essential nutrients and other services. Along the way, they are learning about the complex bargains host cells strike with their microbial partners—trade-offs that can explain some of the features of mitochondria and chloroplasts today.

I was wrong; I think these are bacteria. I think next “up” on the ladder we should look for fungus taking permanent residence in a plant, likely with significant genome movement into the plant, just like how much of our mitochondria’s DNA ended up in our nuclear DNA.

[Wesley_Clark]

Aren’t social animals a form of this happening among advanced organisms? You give up some of your freedom in exchange for a division of labor and the security of the group. Granted they maintain their physical independence, but their minds and behavior unify together.

[Ruken]

Also I’m not so sure about the “has to live in a gamete” thing. The endosymbiont could infect the cells after fertilization.

[lazybratsche]

One example along the lines that Ruken is thinking is the bacteria Wolbochia. These bacteria live in the germline of many arthropod species. In many cases they are parasitic, but some species have evolved mutualistic relationships with their hosts. To take the example I am most familiar with, in fruit flies, Wolbochia are carried in the germ line and transmitted through eggs to the next generation. When an infected female mates with an infected male, it has greatly increased fertility (compared to uninfected females). However, sperm from infected males is not capable of successfully fertilizing *uninfected *eggs! Therefore Wolbochia provide an advantage to their host (increased fertility), but with a significant trade-off (infertility with uninfected females).

Apparently in other species, *Wolbochia *manipulates the reproduction of its hosts in all sorts of crazy ways. There’s even been some horizontal gene transfer between *Wolbochia *and its hosts. There’s a good article here.

(Some, but not all, scientists refer to *Wolbochia *as an “endosymbiont”. Others just say that it is a mutualistic or parasitic intracellular bacteria.)

[vomit_comet]

There are some trees in Africa that, when being over eaten by the local animals, the trees produce this pheromone or other airborne chemical that signals other trees in the area, those trees then start producing a toxin that kills the animals that were foraging on their leaves.

I guess you could call that symbiosis; if the tree population is devastated then all the animals that eat them die whereas if the remaining animals can travel to an area where the trees haven’t been affected, and aren’t producing the toxin yet, some of the animal population will survive.

[EdwardLost]

@whc.03grady

The phenomena of I’m thinking about something like caterpillars and moths/butterflies: could it be that caterpillars and butterflies were once independent organisms that somehow got themselves together for their mutual benefit?

The biologist Lynn Margulis (who introduced the idea that mitochondria originated as endosymbiotes) has also suggested this idea of larva/adults originating as merged organisms. I don’t know if she included caterpillar/moths in that scheme, but I know she did include such things as sea urchins and their larvae as having originally been separate animals that formed a tight symbiotic relationship and then, somehow, got their genomes merged.

[Ruken]

I should have read more from that article:

At the meeting, Patrick Keeling, a protistologist at the University of British Columbia, Vancouver, in Canada, described his studies of a more recent example of this process, called tertiary endosymbiosis. Some dinoflagellates, single-cell aquatic protists, no longer have their original chloroplast, relegating some of its light-sensing apparatus to a cellular component dubbed an eyespot. But they have replaced it by taking in a diatom, a single-celled alga that has its own photosynthetic machinery. The dinoflagellate still carries the diatom’s nucleus and mitochondria, but “I would challenge anyone to say this is not an organelle,” Keeling says.

The dinoflagellate takes in a diatom, which is a eukaryote. The other examples were with prokaryotes. I’m not sure how reproduction works here. But I think it fits what the OP is looking for. Cool stuff.

[Smeghead]

@Ruken

Science 31 October 2014:
Vol. 346 no. 6209 pp. 532-533
DOI: 10.1126/science.346.6209.532
I was wrong; I think these are bacteria. I think next “up” on the ladder we should look for fungus taking permanent residence in a plant, likely with significant genome movement into the plant, just like how much of our mitochondria’s DNA ended up in our nuclear DNA.

Lichen

[Ruken]

@Smeghead

Lichen

Typically not endosymbiosis, although if anywhere, it would be least surprising to see it here.