Female seahorse transfering her eggs to male’s pouch
Do you think you could explain why some animals live for so long compared to others?
Why do some things live longer than others? Well, simplifying a bit, but longevity is essentially a measure of how long a living system can tolerate constant damage before said damage overwhelms it, and the animal dies. The reason why some animals can tolerate this damage for longer than others is, fundamentally, down to two things:
i) Metabolic rate: basically, how quickly the biochemical and physiological processes within a body turnover (how quickly cells grow and divide, how fast one can breakdown and/or produce energy to fuel growth etc.). In cold-blooded creatures (most of them), environmental temperature plays an important role here.
ii) Repair mechanisms: all living bodies are remarkable in that they are always, every second of the day, repairing the damage that’s being constantly done to them. Legions of proteins are busy patching up mutations to your DNA and damage to your cells, ensuring they can continue growing, working properly and dividing (and not becoming cancer!).
Now, the reason why some animals live longer than others is because different animals have differences in both of the above.
Animals with higher metabolic rates accumulate damage more quickly than those with lower metabolic rates – warm-blooded mice, with high rates, only live a few years; cold-blooded, deep-sea molluscs, with very low rates, can live hundreds.
Worth mentioning, an important aspect of cell ageing is telomere length. At the end of each chromosome in a cell, there’s a long stretch of DNA that codes for nothing, but effectively protects the rest of the DNA from damage – called a telomere. Every time a cell divides during growth, a chunk of telomere is broken off and isn’t replaced. After a number of divisions, this constant chipping away at the telomeres reduces them to a critically short length, and the cell dies. You can see why a higher metabolic rate would therefore cause cells to die more quickly (and therefore, ultimately, the animal) – the telomeres take less time to hit this critical threshold as the animal cells are dividing more rapidly.
As for repair mechanisms, some animals have more efficient mechanisms than others. For example, telomeres can be repaired, and some organisms have the mechanisms to do so. As such, you’d expect those animals – such as lobsters, some turtles, many corals, Hydra, and Turritopsis dohrnii (a really cool jellyfish!) – to live longer, and they do! Hydra and the jellyfish can repair their telomeres so well, along with some other biochemical tricks, they’re effectively biologically immortal and cannot die of old age.
he was talking about the fact that some type of shark lives for upwards of 500 years or something.
The shark you’re referring to is likely the greenland shark (Somniosus microcephalus). A study published last year determined the age of one particular individual to be 392 ±120 years old (so a maximum of 512 years, though take that with a pinch of salt!). The reason why they can live so long is, as above, because their metabolic rates are incredibly low; their body processes turn over at a very slow rate and consequently they age slower.
some deep sea creatures are practically immortal as they just create copies of themselves and whatnot.
I mentioned the jellyfish above, which can repeatedly reverse the ageing-process and ‘grow up’ again and again, but there are also many slow-growing deep-sea corals and sponges that can live a helluva’ long time, and for all intents and purposes could also be said to live ‘indefinitely’.
Hexactinellid sponges, for example, have estimated ages up to about 15,000 years. Said value originally comes from this paper, where they used computational modelling to estimate ages based on growth rate. The figure churned out at the end was 23,000 years – though the habitat it was found in is at most 15,000 years old, so obviously off by a bit! I’d take such values with a pinch of salt.
Other sponges, such as the giant barrel sponge, have likewise been estimated to live up into the low thousands. Based on growth modelling again, one particularly large (albeit dead) specimen was thought to be 2,300 years old.
The body plan of these animals is clonal and modular though (a bit like plants, they aren’t restricted to a specific size/shape etc.), as opposed to unitary (like us, with a specific size and body plan, with two arms, two legs etc.), and so the very idea of an individual breaks down – so it’s debatable whether you can truly consider them ‘immortal’ individuals, or self-replicating colonies of successive mortal individuals. It’s up to you how you wanna’ cut it!
Perhaps consuming food like this will make a difference?
superawesomeman08: At first I was all “that’s a small potato…”