There is a parasite which make different amphibians specially frogs and toads to get multiple extra limbs during the transition from tadpole to adult. The objetive of the parasite is to harm the host's locomotion to be predated easier and complete its life cycle infecting the frog's predator.

Is intrisencal to this parasite alterate the growing of the tadpoles to get useless limbs, but what if the parasite would turn to a symbiote, could this be a way to get extra limbs to be used in differen works or permite more advanced regeneration.

The problem is why or what kind of enviromental pressures make the parasite to need improve the host instead of harm it?

  • $\begingroup$ Same as parasite, there is no difference. You said yourself, and I would confirm, that if it could produce positive deviations we would call it symbiote - there is no difference except the outcome. The problem is - there are 1000 ways to make useless things and 1 to make useful one. Wait another billion years and they will melt deeper and figure things out. When it happens we still, can find flaws in created situation, as it will stabilize/freeze evolution capacities of those frogs, but in harsher mutagenic conditions it could be a good thing. Root is in complexity of achiving desired outcome. $\endgroup$
    – MolbOrg
    Commented Aug 22, 2021 at 15:16

2 Answers 2


Maybe it already is a symbiote.

salamander with broken tails

Here is that flatworm parasite. https://www.nationalgeographic.com/animals/article/110802-frogs-deformed-parasites-animals-environment-mutants

I thought if the frogs could detach their limbs like some salamanders can detatch their tails, predators would eat the twitching loose leg while the frog escapes (with all its real legs), and the flatworm in the extra leg can ride it into the belly of the frog predator.

  • $\begingroup$ But the article mentions that the parasite is harmful for the frog, because reduce the locomotion capacities. $\endgroup$
    – Drakio-X
    Commented Aug 24, 2021 at 1:57
  • 1
    $\begingroup$ Yes; that is how it works in real life. I was extrapolating from the interaction as you requested: "what if the parasite would turn to a symbiote, could this be a way to get extra limbs to be used in differen work". The differen work here is attracting predators and letting the host frog escape. $\endgroup$
    – Willk
    Commented Aug 24, 2021 at 12:12

Get rid of the primary host

While a mutually beneficial symbiotic relationship can form just on the existing pressures if the primary host, birds, become immune or their population dwindles in the area, then the parasite would need to find another way to survive. While this doesn't ensure a symbiotic relationship forms if a small minority of frogs have benefited then the groundwork has already been set.


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