> You can't shrink down to the size of an amoeba without losing parts of yourself. That's the lesson one researcher is taking away from a microscopic analysis of the fairy wasp (Megaphragma mymaripenne), which at a mere 200 micrometers in length is one of the world's smallest animals (shown compared to a paramecium and amoeba above). When the scientist compared the neurons of adult and pupae fairy wasps, he discovered that more than 95% of adult neurons lack a nucleus.
> The smallest insects are comparable in size to unicellular organisms. Thus, their size affects their structure not only at the organ level, but also at the cellular level. Here we report the first finding of animals with an almost entirely anucleate nervous system. Adults of the smallest flying insects of the parasitic wasp genus Megaphragma (Hymenoptera: Trichogrammatidae) have only 339–372 nuclei in the central nervous system, i.e., their ganglia, including the brain, consist almost exclusively of processes of neurons. In contrast, their pupae have ganglia more typical of other insects, with about 7400 nuclei in the central nervous system. During the final phases of pupal development, most neuronal cell bodies lyse. As adults, these insects have many fewer nucleated neurons, a small number of cell bodies in different stages of lysis, and about 7000 anucleate cells. Although most neurons lack nuclei, these insects exhibit many important behaviors, including flight and searching for hosts.
> Researchers believe the wasp can survive without nuclei because of its short lifespan; the proteins manufactured during the pupal stage last the animal long enough to complete its life journey.
Interesting, but not surprising — DNA, and the cellular nucleus itself, aren't truly required to make our cells "go". (At least over the span of a few days.)
That is, after all, what radiation poisoning is: a complete destruction of your DNA in your cells, while the cells themselves (attempt to) continue to function. And they do! For some number of days. And that's without any of our evolutionary ancestors ever having been under evolutionary pressure to live without DNA (as far as we know.)
IIRC, cell death from radiation poisoning follows a bathtub curve.
• There's firstly a lot of immediate cell death from apoptosis — probably due damaged DNA starting to do something that looks like cancer, and autolyse safeguards activating in response. This is what a radiation "burn" is.
• But then, after that, everything's actually fine for a while. You're just sitting there for a few days, operating normally — despite the majority of your cells now having massive holes shot through their DNA, with any attempt to unzip that DNA to copy it failing.
After that few days, you get massive waves of cell death — the part of radiation poisoning that actually kills you. This likely arrives, due to cells experiencing various inputs that they see as triggers to attempt some kind of state-transition (whether a minor one, between e.g. glucose vs ketone metabolism; or a major one, e.g. into mitosis.) And doing that requires flipping some epigenetic methylation switches to start producing different proteins — which requires the DNA be un-rolled and re-rolled. The cell tries it; it fails; and there's no "error handling" for the case of "you started a state transition but can't connect to the blueprint database", so the cell just "deadlocks" in a volatile state — e.g. one where metabolism is shut down, so purine waste builds up until the cell lyses for chemical reasons.
So it's not too surprising that an organism could evolve to just intentionally not trigger such cellular state-transitions — likely no longer expressing any of the state-transition "machinery" at all. Such an organism would get quite far with their cells just "doing the thing they were programmed to do", without a nucleus. Even cellular metabolism would continue!
There'd just be nowhere to get "replacement parts" for proteins as the original proteins break down or get oxidized by some radical — thus the lifespan limit.
Also, something not mentioned in what you linked, but which seems like an obvious corollary: I would guess that such organisms would likely be "metabolically fragile." I.e., they likely have dropped anything like adrenaline signalling, as the whole point of that is to get cells to state-transition. So they'll be a bit like a person taking alpha-blockers, who gets winded extremely easily because the drugs are preventing their cells from "gearing up." For this organism, there are no other gears to switch to. The organism is a fixie.
> On a cold day of 2 December 2001, three inhabitants of Lia (later designated
as Patients 1-DN, 2-MG and 3-MB) drove their truck approximately 45–50 km
east of Lia to collect firewood. At around 18:00, they found two containers —
metallic, cylindrical objects — lying on a forest path. Around them, the snow
had curiously thawed within a radius of approximately 1 m, and the wet soil
was steaming. All three individuals stated that the two, rather heavy, cylindrical objects (8–10 kg, 10 cm × 15 cm) were found by chance while carrying out their usual task of collecting firewood.
> One of the three men (Patient 3-MB) picked up one of the cylindrical
objects and, finding that it was hot, dropped it immediately. They planned to
place the gathered wood in their truck the next morning, and because it was
getting dark, they decided to spend the night in the forest, using the hot objects they had discovered as personal heaters.
Section 6 on page 36 is where it gets NSFL. It only gets worse as you continue going through the timeline. There are pictures - they are not for the weak of stomach.
Section 4 is neat from the engineering perspective... "how do you move something that is radioactive enough to melt the snow around it?"
Jesus, that's rather awful. Guess these guys had never heard of radiation. Seems incredible, but I have no idea what the media was like in Georgia 20 years ago (or now, for that matter).
Deinococcus radiodurans is amazingly radiation resistant. Saw a recent update that a single protein was identified that's part of the radiation resistance. When transferred to e.coli it made 40x more radiation resistant.
https://www.science.org/content/article/scienceshot-amoeba-s...
> You can't shrink down to the size of an amoeba without losing parts of yourself. That's the lesson one researcher is taking away from a microscopic analysis of the fairy wasp (Megaphragma mymaripenne), which at a mere 200 micrometers in length is one of the world's smallest animals (shown compared to a paramecium and amoeba above). When the scientist compared the neurons of adult and pupae fairy wasps, he discovered that more than 95% of adult neurons lack a nucleus.
https://www.sciencedirect.com/science/article/abs/pii/S14678...
> The smallest insects are comparable in size to unicellular organisms. Thus, their size affects their structure not only at the organ level, but also at the cellular level. Here we report the first finding of animals with an almost entirely anucleate nervous system. Adults of the smallest flying insects of the parasitic wasp genus Megaphragma (Hymenoptera: Trichogrammatidae) have only 339–372 nuclei in the central nervous system, i.e., their ganglia, including the brain, consist almost exclusively of processes of neurons. In contrast, their pupae have ganglia more typical of other insects, with about 7400 nuclei in the central nervous system. During the final phases of pupal development, most neuronal cell bodies lyse. As adults, these insects have many fewer nucleated neurons, a small number of cell bodies in different stages of lysis, and about 7000 anucleate cells. Although most neurons lack nuclei, these insects exhibit many important behaviors, including flight and searching for hosts.
And the Wikipedia article for the species - https://en.wikipedia.org/wiki/Megaphragma_mymaripenne
In particular:
> Researchers believe the wasp can survive without nuclei because of its short lifespan; the proteins manufactured during the pupal stage last the animal long enough to complete its life journey.