On the Many Mysteries of the European Eel | Hacker News Reader

On the Many Mysteries of the European Eel

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48 pointsbookofjoe13 comments

Before reading Patrik Svensson's "The Book of Eels", I first read the New Yorker article from May 2020 [1] (and corresponding HN post [2]). The article is very much worth the read.

[1] https://www.newyorker.com/magazine/2020/05/25/where-do-eels-...

[2] https://news.ycombinator.com/item?id=23265000

> ... leptocephalus larvae ...

> ... glass eel ...

> ... yellow eel ...

> ... silver eel ...

Eels are nature's Pokemon!

> It’s a long, ascetic journey, undertaken with an existential resolve that cannot be explained. But once an eel reaches the Sargasso Sea, it has, once again, found its way home. Under swirling blankets of seaweed, its eggs are fertilized. And with that, the eel is done, its story complete, and it dies.

I know this should be read more as poetry, but the existential resolve can be explained perfectly well: if an eel lacks it, it will never reproduce and its genes will be lost. Thus, only genes which guarantee that resolve are left in the pool.

Well to really see the issue I think you need a contrast: Why do eels make an enormously long journey, when other species don't? Why can we do it closer to home and they not?

"Why" can be a confusing word when talking about evolutionary history, because the answer is necessarily self-referential: eels do it this way because it's a successful adaptation, and they got to this point through a series of successful adaptations that worked at each step.

Yes, why is an open ended question, but there are better and worse answers.

In this case we might ask, are they better or worse off making the journey than they would be staying at home? Do they gain something from all of that effort? A more genetically diverse mating pool?

Or could it be that it is worse, but they are stuck in a nash equilibrium where any single deviant would be worse off, so there is no viable path to better behavior.

Or is it their behavior suboptimal, even for the individual, but remains because so much is built on top of it that it would be hard to "refactor" the genome to remove the assumptions of a journey?

I greatly prefer the writing and style and writing of the first half compared to the second. Almost seems like it could have been two different articles. Or interwoven between.

You're not too far from the truth: in fact it's two different chapters from the same book, concatenated together into a single article. From what I can tell the style of the book is to interleave these two different stories in alternating chapters: one, a natural history of the eel as a species; two, a personal memoir of the author's childhood fishing for eels with his father.

Fun fact: Freud once spent a summer in Italy dissecting 400 eels in a futile search for their testes.

It wasn't futile - he did find a specimen with testes. It's unclear whether it had just for some reason developed into a male early or if it had been caught in the ocean on its way to the Sargasso Sea.

These and other obscure but fascinating facts are yours for the taking in The Book of Eels. Well written, great read, even if you're not interested in eels to begin with. Why not jog your brain and try something outside of the box this holiday?

While I haven't read Freud's paper [0] myself, and I know that there are a couple of pop history/science accounts that say that [1], there are also a bunch that don't [2]. A bit of googling drags up this account by a guy who seems to have actually read the paper:

>In 1874 Dr. Syrski had announced the most recent solution. He had discovered a small lobed organ and described it as the testes of the eel. Carl Friedrich Claus, chief of the Institute for Comparative Anatomy in Vienna, assigned to his student Freud the task of checking Syrski's observations. Freud dissected 400 eels, finding the Syrski organ in many of them. On microscopic examination he found the histological structure of the organ such that it could well be an immature form of the testes, though he found no definite evidence that this was the case. [3]

Modern researchers propose that Syrski's organ is an optional precursor to the testes [4].

[0] For the German readers among us who wish to settle this debate decisively https://archive.org/stream/sitzungsberichte75kais#page/n367/...

[1] https://www.historytoday.com/archive/natural-histories/sexua... https://biodiversity.utexas.edu/news/entry/sigmund-and-his-e...

[2] http://nautil.us/issue/88/love--sex/eels-dont-have-sex-until... (an interview with the author of TFA) https://twitter.com/greenleejw/status/1205524393490833408 (This is where I originally picked up the fact, strongly recommend you follow if you have even a passing interest in medieval eel facts)

[3] https://www.jstor.org/stable/26301225

[4] https://www.researchgate.net/profile/Benjamin_Geffroy2/publi... (pdf)

The second to last paragraph on page 420 sums it up:

> My investigations now lead me to confirm Syrski's data almost throughout. However, the histological examination of the organ does not make it possible for me to agree decisively with the opinion that this is the testis of the eel or to refute it with certain reasons.

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