Fresh Water

Discussion in 'Physiology and Biology' started by ArchyNorth, Feb 8, 2005.

  1. ArchyNorth

    ArchyNorth GPO Supporter

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    Hey gang,

    Had a question pop into my head.

    Are there any Cepholapods that can live in Fresh Water? Part time or full time?
    I have read about some species of squid living in estruary water (brackish), but have never heard anything about fresh water.

    Would be very interesting to find some land locked fresh water Cephs.

    Thanks
     
  2. cthulhu77

    cthulhu77 Titanites Supporter

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    I have occasionaly seen "freshwater octopus" for sale on trade pubs, but they always turn out to be false...as far as I know, there is no such thing...rather odd, actually !!! One would think that such a successful animal would have found a way to cope with fresh water...one of the mysteries of life, I suppose...
    greg
     
  3. DHyslop

    DHyslop Architeuthis Supporter

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    It doesn't surprise me much--the amount of surface freshwater is so miniscule compared to seawater. And its not just with cephalopods, but taxonomic diversity in general is much higher in seawater...whole phyla that aren't represented at all in freshwater: sponges, cnidarians, etc etc.

    Dan
     
  4. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    Hi Dan - there are quite a number of freshwater sponges and coelenterates (not sure about anemones - Actinaria - though); there are also a number of freshwater bryozoans. Just no FW cephalopods or echinoderms.
     
  5. snafflehound@work

    snafflehound@work O. bimaculoides Registered

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    In a Russian science fiction novel from the 1960's I'm rereading there is a bit about octopi colonizing freshwater near Lake Baikal in the middle of the 21st Century.

    Actually these authors (Arkady and Boris Strugatskii) have several ceph bits in their books. There is one short story where three characters descend into the sea of Japan in a mini-sub armed with explosive torpedos to hunt and kill the giant squid that has been raiding their whale herds. There's also another short story where some suicides on one of the islands near Sakhalin are revealed to be the result of a giant Ordovician ammonite (still somehow alive today in the manner that Nessie is considered to be a surviving plesiosaur) that hunts with a "poisonous biofield", whatever that is.

    Maybe I should make a more detailed post about this in the C&E forum.
     
  6. Barnstorm

    Barnstorm Blue Ring Registered

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    I used to keep freshwater Hydras. Cool little buggers, much like anemones but alot easyer to keep.
     
  7. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    A major difference between the two being that the anemones (Actinaria) have completely lost the medusoid phase of the life cycle. Of course someone will write a paper one day (if it hasn't been written already) reporting the first medusoid stage in an actinarian ..... but that's science.
     
  8. Fujisawas Sake

    Fujisawas Sake Larger Pacific Striped Octopus Supporter Registered

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    I spoke with HSU's lab technician Grant today about the GPO they had in captivity and this subject came up. He theorized that the lack of freshwater cephs is due to their use of hemocyanin as their circulatory fluid.

    Hemocyanin serves as a good transport, but has a low affinity for, oxygen. Freshwater is more dynamic in the O2 and salinity (ionic) changes than seawater. Fish, utilizing the more oxygen-efficient hemoglobin, were able to colonize freshwater first, and therefore were able to keep this niche well-stocked and defended.

    Interesting thought, but it leads me to another question about evolutionary biology in general... If cephs were able to suddenly utilize a more efficient means of oxygen exchange (say, an iron-based pigment like hemoglobin, instead of the less-efficient copper-based hemocyanin), would that make a difference? If so, how many such quantum leaps in physiological changes may have led to rapid changes in evolution in the past? Could a mutation that affects something like blood-O2 affinity lead to a whole new pattern of lifestyle and/or behaviour?

    Who knows?

    John
     
  9. cthulhu77

    cthulhu77 Titanites Supporter

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    Now you have gone and done it again, John !!! My mind is spinning!
    :read: greg
     
  10. monty

    monty Colossal Squid Staff Member Supporter

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    When I was reading up on copper's negative effects on cephs for a thread a week or two ago, one of the articles pointed out that sometimes hemocyanin gets a bad rap for its lower O2 affinity, it has some other advantages that make it more competitive with hemoglobin than just the affinity would suggest. There are certainly plenty of freshwater and land inverts that use it for O2 transport, so it seems like in and of itself it's not a big limiter-- although most freshwater molluscs are pretty sluggish, and a lot of insects are quite fast and active... I've read conflicting things on O2 in cephs-- on the one hand, it's claimed that they're less tolerant of being temporarily deprived of O2 than hemoglobin users, but on the other some cephs (nautilus?) have some nifty mechanism to survive effectively in low-O2 conditions. Certainly, since many live in deep water with a lot less O2 saturation, there's been a lot of evolutionary pressure for those sorts of adaptations...

    I've frequently been amazed at how conservative animal genomes are, once they've hit on a "successful" model... often, certain patterns that were successful in one particular niche really get locked into the genome, and a lot of diverse critters get formed by making small changes but keeping the basic patterns. That's one reason I really like thinking about cephs, because the cephalopod pattern diverged from the vertebrate one a long time ago, and at a very phenotypically simple stage, so they're really the only neurologically "advanced" animals with which we share so little history (possible exception for certain insects, but their "intelligence" seems less clear-cut to me). However, even there, the basic segmented, bilaterally symmetric body plan controlled by the homeobox genes was well-established before the divergences of insect, mollusc, and vertebrate, so we're not as different as we could be...

    Anyway, I suspect that the use of hemocyanin is very well established evolutionarily, such that it's pretty unlikely that such a drastic change could occur naturally; I bet it's so entrenched in intereactions with other systems and the genes that control them that a change that major would require many other simultaneous changes to avoid being lethal just by breaking the system. I bet that there is some very strongly conserved pattern of interaction in cephs' genetic legacy that favors salt water pretty strongly, just because I can't think of any other reason why they wouldn't be around in freshwater. In fact, I know the oceans were a lot less salty when the early cephs were so dominant, so at least they could handle the freshwater-ness. I think the theory that freshwater has less of an O2 buffer is a possibility, but that's more of an issues for rivers, streams, and ponds; there are still freshwater lakes and semi-freshwater estuaries that are more ocean-like in terms of having a pretty consistent O2 level that could serve as an evolutionary stepping-stone. And heck, there are octopuses that live in tidepools, where both the salinity and O2 levels can fluctuate pretty wildly.

    Since cephs were established as free swimmers so much earlier than a lot of the modern forms of life, I bet that they established a lot of genetic "weight" on the systems that were very effective for that era, and probably "locked themselves in" to some things that were selected for very strongly early on, but were sub-optimal when other critters arose. The giant axon seems like a good example of this-- when myelinated axons sped up nervous systems in fish, the squids had to improve their escape reflex, and (I'm guessing because of this genetic lock-in) rather than developing their own myelin, they just scaled up the neuron design that was successful for so long, and made it bigger for faster transport.

    Hmmm.

    Of course, even if there are conservative genetic reasons cephs are unlikely to have point mutations to switch to hemoglobin or freshwater or what-have-you, the "mad scientist genetic engineer" :oshea: :twisted: approach could let us pick and choose things that could never occur as point mutations...
     
  11. Fujisawas Sake

    Fujisawas Sake Larger Pacific Striped Octopus Supporter Registered

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    I don't think that it (the lack of freshwater cephalopods) is completely based on hemocyanin either, but that's a good start.

    The hemocyanins used by arthropods and molluscs is a quite a bit different from each other (there are several papers out there dealing with theories on convergent evolution), and we're talking a hell of a lot more than a simple point mutation to go from hemocyanin to hemoglobin, but still a slight change in blood proteins can make a lot of difference. Even then, I doubt this was entirely the case.

    I still think that fish were just far better at competition. Cephs have a decent metabolic rate, but fish are far better at exploiting new underwater niches. They also have muct better osmoregulatory systems. Maybe a less specialized prey menu might have helped too.

    Interesting thoughts, though. I enjoy physiological evolution topics.

    John
     
  12. n82rboy

    n82rboy Blue Ring Registered

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    This site rocks... thanks guys! :mrgreen:
     
  13. Snafflehound

    Snafflehound GPO Registered

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    I don't think you would get a sudden switch from hemocyanin to hemoglobin as a mutation, any more than you might expect a human to be born with feathered bird wings.
     
  14. Fujisawas Sake

    Fujisawas Sake Larger Pacific Striped Octopus Supporter Registered

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    Well, my friend Thomas brought up a good point today. He said that I was overthinking this situation. Chances are, there were several factors that prevented freshwater colonization of cephalopods, but all were due to its behavioural ecology.

    Case in point: octos hunt crustaceans mostly. The majority of the crustacea are still marine. There would have been no need to try new hunting grounds if no need presented itself. The behaviour wouldn't change, so no selective pressure, therefore no evolution toward a freshwater existence.

    Another point; osmoregulation. Cephs don't handle freshwater. They are by their nature isosmotic with the seawater and freshwater would stun and most likely kill a ceph quickly. Their metanephridia are no where near as hardy as our kidneys, which are pretty fragile. Fish are better at taking the extremes of freshwater by highly developed kidneys. Very few molluscs are freshwater, and those that are show signs of having returned to the water from a land-based life (pulmonate gastropods).

    Just another :twocents:,

    John
     
  15. snafflehound@work

    snafflehound@work O. bimaculoides Registered

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    Zebra mussels returned to the water from a land based life! ! ?? !
     
  16. monty

    monty Colossal Squid Staff Member Supporter

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    wasn't the ocean salinity a lot lower when molluscs first arose, though? It seems more plausible that there is genetic leftover that could be reverted to as a pretty simple mutation that could allow them to live in freshwater environments...

    - M
     
  17. Fujisawas Sake

    Fujisawas Sake Larger Pacific Striped Octopus Supporter Registered

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    Sorry, force of habit from staring at a tank full of periwinkles while I'm typing.

    Monty,

    Given the amount of specialized adaptation of the cephalopod metanephridia, as well as the amount of necessary ionic concentration in their cells, I doubt a simple mutation would suffice here, though I would say its far from impossible.

    Good point about early ocean salinity. I would definitely like to find out more about that.

    John
     
  18. snafflehound@work

    snafflehound@work O. bimaculoides Registered

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    oh, i thought maybe you were going to provide evidence that they evolved from barnacle geese
     
  19. chrono_war01

    chrono_war01 Colossal Squid Supporter

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    all this is too much for my 5-byte brain. Error! *Chrono's brain explodes*
     
  20. Steve O'Shea

    Steve O'Shea Colossal Squid Supporter

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    To slightly digress, and to split an infinitive in the process ... are there any *giant* freshwater invertebrates?
     

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