6 ms·

Whale sharks: Atomic tests solve age puzzle of world's largest fish

94 points by willvarfar 7y ago

Zenst 7y ago
"Over time, every living thing on the planet has absorbed this extra Carbon-14 which still persists." Is that as consistent in absorption? More so animals that feed upon different levels and maybe more so - do plankton absorb more or less and any animal feeding upon them would see a higher rate perhaps. I'm still looking into these aspects - fun google time. #1 Another train of thought I have from reading this is: We may well read in the future about plastic pollution being used to measure metrics in life forms. [EDIT ADD] #1 https://en.wikipedia.org/wiki/Carbon-14 https://en.wikipedia.org/wiki/Carbon-14 It is naturally formed by cosmic rays, it has also been measured as highers in area's that atomic testing happened (so near Australia) and with that, Southern hemisphere. Given that, one would expect, any life form that was located near area's near the poles or southern oceans would be more exposed to the natural and atomic unnatural sources and whilst the unnatural sources would dissipate - anything exposed during the early times would also have higher levels than such a lifeform in those same area's today due to decay and dispersion.
- gus_massa 7y ago
  I think you can assume they didn't change the diet too much, so before 1945, measuring the carbon in the bones(?) you should get a nice smooth exponential curve, and then a jump in 1945 [Is there a small delay?]. More details in https://en.wikipedia.org/wiki/Bomb_pulse https://en.wikipedia.org/wiki/Bomb_pulse
  - Zenst 7y ago
    Whilst their food would not of changed in source, the content would of had spikes above global average it periods of time due to the atomic spike, also how that dispersed and how long until equilibrium would all be factors that come into play. Let alone natural hotspots from solar radiation increase near the poles. But then the error +/- rate would seem to accommodate those kind of margins, but always nice if there is a way of narrowing those margins, so may be a field of research that has some headroom and also help learn many other tangents and maybe another data point for historical solar radiation.
walkingolof 7y ago
A method like this was used to determine the age of the Greenland shark, a large shark living in cold waters. "In 2016, a study based on 28 specimens that ranged from 81 to 502 cm (2.7–16.5 ft) in length determined by radiocarbon dating of crystals within the lens of their eyes, that the oldest of the animals that they sampled, which also was the largest, had lived for 392 ± 120 years and was consequently born between 1504 and 1744" https://en.wikipedia.org/wiki/Greenland_shark https://en.wikipedia.org/wiki/Greenland_shark
- pvaldes 7y ago
  > had lived for 392 ± 120 years Is the same problem, I personally (is just my opinion) wouldn't discard that where 392 solid meals instead, one seal or reindeer at a time boosting grow periods between nape and nape, minus an unknown number of pregnancy events. Scientists are forced to publish something, anything, in short periods of time, so here we are. And is getting worse.
  - bpodgursky 7y ago
    Radiocarbon dating wouldn't be affected by meal frequency, unless I'm missing something. It's just identifying the oldest material in the specimen.
    - pvaldes 7y ago
      We have two main different ways to attack the problem of age, and both have issues > But as scientists know the rate at which this isotope decays, it is a very useful marker in determining age... The older the creature, the less Carbon-14 you'd expect to find. They are registering decay in the level of carbon-14. The clock is adjusted for bone (storing this isotope as a more or less permanent crystalline mix of carbone and calcium). This is cartilage. And teeth in sharks last only for some period ranging between, lets say, two weeks and two years (100 days for a white shark or so). Somewhere inside this period, those pieces storing carbon-14 will fall and will need to be replaced in a few days. If the reserves are mobilised from vertebra to tooth, then you would expect to find much less carbon-14 than usual. Therefore you could conclude than the fish is much older than it really is. Counting the number and type of rings on vertebra is a different problem, and is affected by fasting and starving periods.
hprotagonist 7y ago
You can play a similar radiocarbon dating trick with the lenses of greenland sharks. They live to about 390 +/- 120 years old, and are estimated to reach sexual maturity at 150 years old. A specimen analysed in 2016 was born somewhere between 1500 and 1740. https://science.sciencemag.org/content/353/6300/702.full https://science.sciencemag.org/content/353/6300/702.full
pvaldes 7y ago
In my experience, bony fishes are not easy to date by counting rings. I tried it and discarded the whole work. If you find 20 rings, you can assume that the fish would have 10 years (one opaque ring in summer and other hyaline ring for winter), but unfortunately there are also bifurcated rings, disease's rings, fused and duplicated rings so your animal could have several false duplicated rings, and have only 7 years. In 200 thin rings your error can be awful. To know the sex of the animals is also important, because females will produce extra hyaline spawn rings starting somewhere in their adult phase. And males... well, nobody nows. They obviously do not get pregnant but do the male whale sharks fight and stop eating?. Not to mention than some fishes can change its sex perfectly. This with bony fishes, that have true bones. Big sharks are cartilaginous fishes. Cartilaginous tissue dyes badly and rings in its vertebra are less clearly marked. This animals migrate (vertically and horizontally). This means that would probably starve for long periods and then feast and that their vertebras would be subject to a wide range of pressure that could erase rings. > So any animal that was alive then incorporated that spike in Carbon-14 into their hard parts The key of the phrase is hard parts. They are looking at cartilage, that is not hard and is a very slow growing and inert structure (what if most of all carbone went to the muscle instead?). The only hard part in whale sharks is the tooth (1-5 milimeters long if I remember correctly). Those teeth are lost and replaced continuously so can't be used to age the animal. Even more, they are releasing carbon-14 at a unknown rate. I would like to see how they address this fact as source of error in their models. I remain still sceptical when I read this kind of results. Tagging or photoidentification could help, but our best chance is with captive animals.
- x3n0ph3n3 7y ago
  > I tried it and discarded the whole work. Why wouldn't you publish on how it can't be done reliably?
  - pvaldes 7y ago
    It just didn't pass the cut. I had plenty of other interesting questions to chew, and moved on. There is not reason anymore to revisit it. Most of those bones would be unreadable today in any case.
skoskie 7y ago
100-150 years old.
pjc50 7y ago
It is rather remarkable that nuclear weapons have left a legacy written at the atomic level in every living creature.
- jmiskovic 7y ago
  And not just in living creatures. Ships sunk before atomic tests are valuable source of "low-background steel". https://en.wikipedia.org/wiki/Low-background_steel https://en.wikipedia.org/wiki/Low-background_steel
deleted 7y ago
[deleted]

94 points by willvarfar 7y ago

"Over time, every living thing on the planet has absorbed this extra Carbon-14 which still persists." Is that as consistent in absorption? More so animals that feed upon different levels and maybe more so - do plankton absorb more or less and any animal feeding upon them would see a higher rate perhaps. I'm still looking into these aspects - fun google time. #1 Another train of thought I have from reading this is: We may well read in the future about plastic pollution being used to measure metrics in life forms. [EDIT ADD] #1 https://en.wikipedia.org/wiki/Carbon-14 https://en.wikipedia.org/wiki/Carbon-14 It is naturally formed by cosmic rays, it has also been measured as highers in area's that atomic testing happened (so near Australia) and with that, Southern hemisphere. Given that, one would expect, any life form that was located near area's near the poles or southern oceans would be more exposed to the natural and atomic unnatural sources and whilst the unnatural sources would dissipate - anything exposed during the early times would also have higher levels than such a lifeform in those same area's today due to decay and dispersion.

gus_massa 7y ago
I think you can assume they didn't change the diet too much, so before 1945, measuring the carbon in the bones(?) you should get a nice smooth exponential curve, and then a jump in 1945 [Is there a small delay?]. More details in https://en.wikipedia.org/wiki/Bomb_pulse https://en.wikipedia.org/wiki/Bomb_pulse
- Zenst 7y ago
  Whilst their food would not of changed in source, the content would of had spikes above global average it periods of time due to the atomic spike, also how that dispersed and how long until equilibrium would all be factors that come into play. Let alone natural hotspots from solar radiation increase near the poles. But then the error +/- rate would seem to accommodate those kind of margins, but always nice if there is a way of narrowing those margins, so may be a field of research that has some headroom and also help learn many other tangents and maybe another data point for historical solar radiation.

walkingolof 7y ago

A method like this was used to determine the age of the Greenland shark, a large shark living in cold waters. "In 2016, a study based on 28 specimens that ranged from 81 to 502 cm (2.7–16.5 ft) in length determined by radiocarbon dating of crystals within the lens of their eyes, that the oldest of the animals that they sampled, which also was the largest, had lived for 392 ± 120 years and was consequently born between 1504 and 1744" https://en.wikipedia.org/wiki/Greenland_shark https://en.wikipedia.org/wiki/Greenland_shark

pvaldes 7y ago
> had lived for 392 ± 120 years Is the same problem, I personally (is just my opinion) wouldn't discard that where 392 solid meals instead, one seal or reindeer at a time boosting grow periods between nape and nape, minus an unknown number of pregnancy events. Scientists are forced to publish something, anything, in short periods of time, so here we are. And is getting worse.
- bpodgursky 7y ago
  Radiocarbon dating wouldn't be affected by meal frequency, unless I'm missing something. It's just identifying the oldest material in the specimen.
  - pvaldes 7y ago
    We have two main different ways to attack the problem of age, and both have issues > But as scientists know the rate at which this isotope decays, it is a very useful marker in determining age... The older the creature, the less Carbon-14 you'd expect to find. They are registering decay in the level of carbon-14. The clock is adjusted for bone (storing this isotope as a more or less permanent crystalline mix of carbone and calcium). This is cartilage. And teeth in sharks last only for some period ranging between, lets say, two weeks and two years (100 days for a white shark or so). Somewhere inside this period, those pieces storing carbon-14 will fall and will need to be replaced in a few days. If the reserves are mobilised from vertebra to tooth, then you would expect to find much less carbon-14 than usual. Therefore you could conclude than the fish is much older than it really is. Counting the number and type of rings on vertebra is a different problem, and is affected by fasting and starving periods.

hprotagonist 7y ago

You can play a similar radiocarbon dating trick with the lenses of greenland sharks. They live to about 390 +/- 120 years old, and are estimated to reach sexual maturity at 150 years old. A specimen analysed in 2016 was born somewhere between 1500 and 1740. https://science.sciencemag.org/content/353/6300/702.full https://science.sciencemag.org/content/353/6300/702.full

pvaldes 7y ago

In my experience, bony fishes are not easy to date by counting rings. I tried it and discarded the whole work. If you find 20 rings, you can assume that the fish would have 10 years (one opaque ring in summer and other hyaline ring for winter), but unfortunately there are also bifurcated rings, disease's rings, fused and duplicated rings so your animal could have several false duplicated rings, and have only 7 years. In 200 thin rings your error can be awful. To know the sex of the animals is also important, because females will produce extra hyaline spawn rings starting somewhere in their adult phase. And males... well, nobody nows. They obviously do not get pregnant but do the male whale sharks fight and stop eating?. Not to mention than some fishes can change its sex perfectly. This with bony fishes, that have true bones. Big sharks are cartilaginous fishes. Cartilaginous tissue dyes badly and rings in its vertebra are less clearly marked. This animals migrate (vertically and horizontally). This means that would probably starve for long periods and then feast and that their vertebras would be subject to a wide range of pressure that could erase rings. > So any animal that was alive then incorporated that spike in Carbon-14 into their hard parts The key of the phrase is hard parts. They are looking at cartilage, that is not hard and is a very slow growing and inert structure (what if most of all carbone went to the muscle instead?). The only hard part in whale sharks is the tooth (1-5 milimeters long if I remember correctly). Those teeth are lost and replaced continuously so can't be used to age the animal. Even more, they are releasing carbon-14 at a unknown rate. I would like to see how they address this fact as source of error in their models. I remain still sceptical when I read this kind of results. Tagging or photoidentification could help, but our best chance is with captive animals.

x3n0ph3n3 7y ago
> I tried it and discarded the whole work. Why wouldn't you publish on how it can't be done reliably?
- pvaldes 7y ago
  It just didn't pass the cut. I had plenty of other interesting questions to chew, and moved on. There is not reason anymore to revisit it. Most of those bones would be unreadable today in any case.

skoskie 7y ago

100-150 years old.

pjc50 7y ago

It is rather remarkable that nuclear weapons have left a legacy written at the atomic level in every living creature.

jmiskovic 7y ago
And not just in living creatures. Ships sunk before atomic tests are valuable source of "low-background steel". https://en.wikipedia.org/wiki/Low-background_steel https://en.wikipedia.org/wiki/Low-background_steel

deleted 7y ago

[deleted]