No. “I’m a panda. Look it up.” 
Man, am I an idiot. I thought to myself, “Hmm… something that doesn’t require water to live? Hmm… maybe there’s something that lives on the bottom of the ocean… Oh, wait.” :smack:
The answer is no, unless you start moving the bar from absolutely no water at all.
There are creatures that can exist without H[sub]2[/sub]O, but only because of the interference of people.
Algae and many micro-organisms can survive in heavy water – D[sub]2[/sub]O, and generations of such creatures have been raised in it. The algae has actually proven to be a problem in cooling systems using D[sub]2[/sub]O, because it can clog the system and reduce light throughput. Cgemically, D[sub]2[/sub]O is very similar to normal water, alkthough too much of it will kill higher organisms (like us). Furthermore, heavy water is very rare in the Real World, and only exists in concentrations because people separate it from normal water. Left open, a container of heavy water will exchange water with atmospheric water, and you’ll eventually end up with a container of normal water.
So, although there are organisms that can exist without water, they don’t do so naturally, only live in man-made reservoirs of such fluid, and don’t occur naturally (and aren’t likely to, even elsewhere in the universe).
Unless its life processes are very different from anything currently on earth, any organism is going to need some sort of fluid to move nutrients and waste around, and as a medium for reactions. And, as I once remarked on this Board, it seems as if just about every non-organic liquid at room temperature that isn’t a silicone or a halogenated compound seems to react violently with water. And since water inevitably seems to get into most liquids, I can’t see an inorganic room-temperature liquid taking up the slack in place of water.
Organic liquids don’t seem to support life, either (I think of cases like the sulfuric acid cited above as water with a high hydrogen ion concentration, but if that doesn’t work for you, think of it as a lone counter-example). Alcohols and esters don’t seem to support life. There are bacteria that eat petroleum, but I think that they still use water, and live in water.
I could conceive of life under different circumstances – higher temperatures, or radically lower temperatures, or different combinations of temperature and pressure – giving rise to life processes that use some other fluid, but I’m pretty sure we don’t have them here on earth.
Well, I hadn’t thought of D[sub]2[/sub]O, so I guess there is an exception. Sulfuric acid, of course, has water in it. Most proteins fundamentally need water or, I guess, D[sub]2[/sub]O. You wont have much luck with T[sub]2[/sub]O I’d guess. Remember, proteins and enzymes aren’t just a string of amino acids, they are folded and twisted just right. Water is almost always involved in hydrogen bonding necessary to keep it’s shape. Once you remove the water, it is not likely you will get the right shape back just by adding water again.
IIRC, there’s a limit on substituting D[sub]2[/sub]O for H[sub]2[/sub]O in mammals. The isotope effect slows down electron transport to the point where rats die, or some such.
Bacteria will grow in up to 99.7% D[sub]2[/sub]O, but it’s not clear for how many generations, or what the effect is of removing that last 0.3% H[sub]2[/sub]O.
Higher plants don’t much care for more than about 70% D[sub]2[/sub]O enrichment.
I don’t know about electron transport, but the kinetic isotope effect will slow down certain reactions by about 6 times. It is very pronounced in reactions where the bond making and bond breaking is taking place right at the deuterium.
If the water is 99.7% D[sub]2[/sub]O, then the balance is mostly HDO rather than H[sub]2[/sub]O.
Yes – I was thinking about this after my posting. It occurred to me that HDO is much more common in nature than D[sub]2[/sub]O. But, ironically, since we’re more interested in D[sub]2[/sub]O in the lab, HDO is probably much less common than D[sub]2[/sub]O there.
There probably aren’t many completely anhydrous environments on Earth (at least the surface and crust) - so even if it were possible for such an organism to arise, the opportunity to do so without needing or at least including water is not readily available.
Since Protons/Deuterons exchange readily between two water/heavy water molecules, any H[sub]2[/sub]O/D[sub]2[/sub]O mixture will also contain HDO
Of course – that’s why I said that. My point is that HDO is going to be much more common than D2O in nature. But we’re interested in pure D2O, rather than HDO, so in the laboratory, perversely, we’ll have either almost pure water or almost pure heavy water, but generally not much semi-heavy D2O. The same organisms that live in water or in D2O ought to live in HDO as well, but there will be a lot less concentrated HDO around for them to live in.
I’ll bet your D[sub]2[/sub]O isn’t pure. I don’t know what you use it for. I use it for NMR, and it’s rather important that the sample has some HDO, or we would have trouble shimming.
Undoubtedly – that’s invariably the case. But why are you even making an issue of it?
Only because you were talking about “pure” D[sub]2[/sub]O. I wasn’t sure if you had some ultra-pure D[sub]2[/sub]O for some reason. I don’t even know what such a thing would be used for. You mentioned something about cooling systems.
No, I only meant the D2O you can buy from various sources, meaning that we’ve separated it from most of the normal water and HDO. Inevitably you have some residue of other stuff in there.
love your work, man!
keep it up.
I would regard D20 as being “water” even if a different symbol is used for the heavy hydrogen; chemically it’s the same even if the isotopes are different. We don’t regard carbon or oxygen compounds as being different substances just because they might contain different isotopes.
It’s extremely similar (which is why algae will live in it), but not identical – it’s poisonous to higher life in concentrations, and it is so because its properties differ from those of ordinary water. That means it’s not chemically identical – the slight difference in weight and size of the nucleus do make for differences in reactions. It has a different freezing and boiling point. Its physical chemistry is different. So it’s not just “a different symbol”. In most other elements the difference due to the isotope really doesn’t have a significant effect, but for hydrogen the weight of the nucleus is doubled, and that’s quite profound.
I can see classing this with “water” for several reasons, but i can see more of them for putting this in a separate class.
In any event, there’s no way you’d find large concentrations of this in nature, and thus, the kind of creatures that could inhabit Heavy Water (and, perhaps, not ordinary water) wouldn’t be expected to evolve normally. It’s a minor loophole for the OP’s request, but I claim it’s a legitimate one.
Just to emphasize what CalMeacham has said. For all other isotopes the difference in reactivity is sometimes measurable, but not significant. Think of the bond as a spring attached to two masses. Doubling the mass at one end has an enormous effect on the energy of it’s states. I have the proof in my notes someplace, but it’s mathematically provable with pretty basic physics that T[sub]1/2[/sub] is about six times longer for a reaction where the rate determining step involves breaking a carbon hydrogen bond. It is a great way to study reaction mechanisms.