I've eaten pufferfish on two occasions out in Japan - with no adverse side effects ( :D ). An expensive delicacy which otherwise wasn't all that memorable. Whilst I'm pretty sure no-one eats box jellyfish, I know out in Japan I also sampled the tentacles of a less sinister related species. The texture was memorable in that they were kind of crunchy (if something so soft and delicate can ever be described that way). I would highly recommend for the texture if for no other reason. Taste-wise, I'm pretty sure these too were fairly unremarkable, deriving most of the flavour of the dish from the 'juice' (???) they were served in. Probably vinegar based and fairly watery but it might have been something like mirin???

Hopefully, I'll never have eaten a nematode but I've certainly had to study them in the past.

Good post! And you only live once, eh? :)