Perverted Frogs

Pedophylax esculentus is a common type of frog in Europe. It originated as a hybrid of two other frog species (P. ridibundus (RR) and P. lessonae (LL) ), but that’s not their fault. However, the way in which they continue the species is genuinely embarrassing, almost as bad as puppeteers.

P. esculentus ( genome RL) generally produces offspring by mating with another species, usually P. lessonae. In most populations, they produce gametes that only contain the R genome (the L genome is discarded): mating with P. Lessonae restores the L genome. Presto, more hybrids.

They can mate with others of their kind, but few tadpoles survive – essentially because the parental genome (R) does not go through sexual recombination – thus mutations have accumulated over the many generations since the original hybridization. Muller’s ratchet.

In eastern Europe, it’s the other way around: the L genome is clonal and the hybrids have to mate with P. ridibundus, with complex results (3/4 hybrids, 1/4 pure ridibundus).

And then some populations manage with a mix of diploid and triploid hybrids, which we’ll leave as an exercise for the reader.

Anyhow, the truly weird thing is, people eat these things.

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15 Responses to Perverted Frogs

  1. r321 says:

    Pedo? Indeed. Or Pelophylax?

  2. CharlesK says:

    At some point I stopped reading Niven’s novels. Imaginative, and Pierson’s Puppeteers were well thought out, but I like more science in my science fiction. Even outdated science. I’d rather reread a dry, space travel procedural like Clarke’s The Sands of Mars.

    Or maybe I’m getting old.

  3. MawBTS says:

    Interesting. The way you’ve described them almost makes them sound like a parasitic species, relying on other types of frogs to harbour their young.

    What’s their preference when mating? When given a choice, do P. esculentus seek out P. lessonae and ignore their own kind, or aren’t frogs that smart?

  4. Rum says:

    “People eat these things.” Why not? They taste like chicken.

  5. Henk says:

    I remember this story from “The Extended Phenotype” by Dawkins, but no reference to Pelophylax in the index. Bad memory? Bad index? Turns out our froggies were reassigned from Rana to Pelophylax about a decade ago.

  6. IC says:

    Fascinating! Learn some thing new again.

    • IC says:

      “parental genome (R) does not go through sexual recombination ”

      I wonder whether mules have the similar problems due to lack of recombination between donkey and horse chromosomes. Thus mutational loads become too high even for one generation.

      • IC says:

        Well, I found answer for mule. It is not mutational load issue. But meiosis can not happen due to this:

        “Like I said, a donkey and a horse chromosome aren’t necessarily similar enough to match up. Add to this the unmatched chromosome and you have a real problem. The chromosomes can’t find their partners and this causes the sperm and eggs not to get made”
        So there is no gamets can be made due to different number of chromosome and unmatched structure.

  7. IC says:

    This might implicate some human odd sexual interest like particular individual, enemy (romeo juliet), even interracial situation (60% males open to interracial sex, only 27% female open to interracial sex). All strange sexual interest might have some genetic backgroup need to explore.

    When some individual particularly appealing to your taste, your genes might shape your taste subconsciously to produce the best outcome with that particular individual.

    There is always some individual especially attractive to ourselve own taste, but not to general public. Most time I got comments like ” you have good taste of women'” for my gf except one lady who only appeals to my taste.

  8. ohwilleke says:

    Reminds me of the population genetic rules for vampires in Richelle Mead’s Vampire Academy series of novels. In the novels, there are pure blooded humans, pure blooded vampires and hybrid human-vampires. The hybrids can have children with pureblooded vampires, but not with other hybrid individuals. And, in many possible combinations of the three types, there is no recombination.

  9. Diane Ritter says:

    Do you have a link where the suppression of the L chromosomes is discussed further? This seems like an astonishing mutation, one that would quickly go to fixation anywhere it arose, except in the rare (?) case like the one you describe in the frog, where the sexual recombination of the chromosomes also has become defective. It seems like the mechanism, whatever it is, of discarding the L chromosomes might be an excellent means of modifying undesirable traits in wild populations. Or of driving them to extinction. A quick and easy way to eradicate leeches, mosquitoes, etc.

    The fact that the frogs also have lost the ability of sexual recombination is interesting. They both seem like rare mutations, and so the fact that they both exist in one species makes one wonder if having one leads to the increased probability of developing the other. It is tempting to believe that the ‘L chromosome suppression’ mutation reduced the selective pressure on sexual recombination.

  10. j says:

    Thank you. Finally I understand Arthur Koestler’s book “The Case of the Midwife Toad” that has been long simmering in the back of my mind. He writes about Prof. Kammerer’s laboratory experiments that appeared to reinforce the discredited Lamarckian theory which preceded Darwin’s. The book may have been the last shot in the historical Lamarck- Darwin controversy. Darwin is incompatible with socialism – the paradox is that Darwin won in science, but Lamarck (socialism) rules everywhere, including Europe, China and the USA (and now Bernie Sanders…)

  11. j says:

    This solves the riddle of Arthur Koestler’s The Case of the Midwife Toad. He thought that Lamarck was right, but no, it is that frogs (and Darwinism) are perverts.

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