Life finds a way

There turn out to be a number of cell line infections – contagious cancers – in marine filter feeders, as I suspected a long time ago.

I wonder if some may have evolved a strategy in which they gradually replace the host, rather than just infecting it –  something like a strangler fig.




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23 Responses to Life finds a way

  1. Fun biology story I learned recently: there’s a species of pillbug that can get infected by Wolbachia bacteria, which feminizes the bugs to improve its own survival, as it only gets passed down the maternal line. But in this species, the normal sex chromosomes do not exist. Instead, there’s an integrated copy of the Wolbachia genome that serves as a sex chromosome.

  2. ghazisiz says:

    So this is apparently not about whales, but about bivalves. What would replacement look like? Bivalve gone, something else left behind. What would that something else look like? Should be something known to natural history, like a strangler fig.

    • Jacob says:

      That’s the issue — it could be another of the same bivalve. The quickest or perhaps only way to know would be genetic sequencing.

      For this to be possible, a single cell line would have to have the proliferative functionalities of the cancer, but also the tissue development capabilities of an ordinary bivalve.

      The only reason something as weird/wild as this would be possible is that there have been a bajillion opportunities for it to evolve over a very long time. That’s why the transmissible cancers were so much more likely in bivalves: in land animals, you need direct physical contact (sex in the case of dogs, combat in the case of Tasmanian devils) or a vector (as with hamsters). This isn’t the case with filter feeders.

      • gcochran9 says:

        I know of an example in which cells from a rat teratoma were added to a rat embryo: in that environment, exposed to the right environment, they developed into part of a rat. The rat was piebald: had three parents, two normal and a tumor.

        Ran into this the same afternoon I first read The Boys from Brazil.

        • benespen says:

          Since in general cell line infections seem to have lost the ability to self-organize into the thing they used to be, the cell line would probably need to “borrow” its development environment from its host. Not inherently implausible, especially given that graft versus host disease is a thing. If this was something that happens, an immune response could have developed over time.

        • Jacob says:

          I remember your post about this. I can’t see any reason it wouldn’t work in bivalves.

          I agree with benespen: highjacking developmental cues must be the best way to get this to happen. That’s how it was with the teratomas, but also naturally occurring chimeras descended from fraternal siblings. Someone at my workplace did it with another vertebrate species, merging multiple clonal cell lines — was the first to do so.

          The expected counter-adaptations would protect developing larvae from cell line infections.

          As for the pathogen’s adaptations, I think that it would either usurp the germ line or retain the ability to dedifferentiate and kick off more cell line infections.

          Otherwise, why bother?

      • gabriel alberton says:

        Plus animals like sponges have cells all over them that can change into other kinds of cells. Other sponges could then possibly infect others with said cells. I never studied the topic in detail, but knowing this, it’s not that unlikely many sponges are a mix of different cells from different organisms.

  3. TWS says:

    Isn’t there a fungus that replaces an insect?

  4. Jacob says:

    Bonus points if they usurp the germline.

  5. Jacob says:

    Wouldn’t the first clue here be high rates of chimerism? The second being that the two cell lines are too distantly related to be siblings.

  6. Douglas Knight says:

    What did you suspect?
    That filter feeders were the place to look for contagious cancers?
    Why filter feeders in particular? transmission by shedding cells into the sea?

  7. Erik Sieven says:

    another reason not to eat to much mussels or no mussels at all?

  8. Peripatetic Commenter says:

    Off topic, but to what extent are the various pandemics that have occurred over the last 2,000 years or more resulted in a reduction of variance among humans compared with Chimps, for the simple reason that those who survived such pandemics were likely related to others who survived.

    Fixation can occur when all bearers of all other variants have been killed.

    The increase in population density and the vastly greater distances traveled by some humans would allow diseases to be spread among many more people, but maybe that is a naive view.

  9. Smithie says:

    Could there be giant cancers roaming the deep, and fighting with sperm whales?

    I know it is a stretch, but I like the idea.

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