[News]: Colossal squid was 'lethargic blob' - ABC Science Online

Discussion in 'The Octopus' Den' started by octobot, Aug 22, 2008.

  1. octobot

    octobot Robotic Staff Staff Member Robotic Staff

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    Colossal squid was 'lethargic blob'
    [SIZE=-1]ABC Science Online, Australia - 5 hours ago[/SIZE]
    [SIZE=-1]New Zealand's mysterious colossal squid, the largest of the feared and legendary species ever caught, was not the T-Rex of the oceans but a lethargic blob, ...[/SIZE]


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  2. octobot

    octobot Robotic Staff Staff Member Robotic Staff

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  3. OB

    OB Colossal Squid Staff Member Moderator

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    BAD BAD BAD REPORTING!!! :banghead:

    Not actively swimming might also mean deadly ambush predator, not blobby scavenger by definition. Toothfish on longlines may be immobile, but not dead per se.

    Secondly, the mantle may be (partly) gelatinous (there were still distinct zones of muscle dorsally in the second large specimen we examined in May, Steve may tell us how the Big One fared in this respect; as we weren't able to turn it over then, I got just see the ventral side), the main propulsion comes from the fin, almost resembling a very muscular stingray when viewed up close and personal and basically as *wide as the bulky mantle itself. I am in agreement that M. hamiltoni as an adult female does not appear to be built for great speeds, but her 2 to 4 cm thick gelatinous dermis and slight denticulation of the epidermis certainly indicate adaptations to counter drag, only significant at higher speeds, and bulk is not against the grain of streamlining per se; think bluefin tuna, not exactly a straggler (albeit of 70% muscle).

    As far as I'm concerned I'm not wholly convinced of the argument, here....

    * In nature, redundancy has little place. Muscle tissue has the highest baseline metabolic rate of all squid tissues, bar the CNS. As the latter is miniscule compared to the fin's consumption, it stands to reason that any changes to allow for muscular atrophy towards the end of the life cycle (such as suggested for M. hamiltoni's tentacles) will be favoured and preserved in ensuing generations. The fin, however, does not appear to diminish in size in this species with age. I would like to bring back from memory the still famous picture taken during the initial capture of the living specimen, where the impression of "being quite capable of swimming" IMHO is very convincing, if analogy with other species holds, the fin allows manoeuvring forwards and backwards to the extent of making mantle muscle atrophy a preferred strategy, rather?

    I know, it's all circumstantial, but we can at least fuel debate, funny how this dead squid in an extraordinary jar speaks to us in tongues :wink:
     
  4. monty

    monty Colossal Squid Staff Member Supporter

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    I remember the initial observation being that there was a layer of gelatinous tissue under the skin of the mantle. I had assumed that meant that there was muscle underneath that layer of gelatinous stuff... certainly, the mantle needs to be muscular enough for respiration, but was there really so little muscle that jetting seemed impossible? And was the gelatinous goo examined microscopically or via chemical analysis? I know this isn't a common (known?) thing in cephs, but I'm wondering if it's analogous to fat in mammals: a way of storing energy or protein or something, perhaps in anticipation of egg-laying? The large girth does seem to be a drop in streamlining compared to the younger ones that have been seen, so maybe the females eat voraciously to fatten themselves up before spawning, and can sacrifice some swimming speed for that?
     
  5. OB

    OB Colossal Squid Staff Member Moderator

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    "The layer of gelatinous tissue under the skin" contains large sparse chromatophores, which is why I dubbed it dermis, and I would bet a significant amount of cheap Chianti on it containing collagen. This was, however, not biochemically confirmed, as far as I know. Certainly not in the main specimen, but I am also not aware of any analysis done on the reference specimen. We had a 40x microscope at our disposal, but not a 600x or 1000x, which, together with some appropriate immuno-staining, would've given us these additional insights...

    So, yes, there was a great swath of translucent, almost brittle tissue forming the majority of the lateral and ventral mantle, that had a totally gelatinous consistency and the creamy white of (high density) muscle only in a select band. A forceful finger would poke a hole right through the mantle at its most gelatinous part.

    The funnel on this specimen is a whopper, it would surprise me if no jetting occurs at all, but as I said earlier, its fin is so powerful that it might not need it too much. Think of how Taningia moves forward with its powerful fins in Ku's underwater footage.

    I would argue against the "dermis" being an energy storage structure, it contains enormous amounts of water and the main gelatinous tissue forming the layer between dermis and inner lining would be more appropriate for that. That may actually be slightly muscular, but not at all like what you see in Loligo or Architeuthis, for that matter.

    Interestingly enough these are both relatively "small fin" species with a powerful mantle and reliance on jetting. With Architeuthis, the only concern is always whether its head will drop off, or not :wink: I am thoroughly unimpressed with the latter's robustness in the brachial crown to cranium category...
     
  6. monty

    monty Colossal Squid Staff Member Supporter

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    It seems to me that a large funnel is indicative of weaker jet propulsion. There's a tradeoff: a smaller funnel results in faster water jets, but adds more resistance that has to be overcome by muscle... think of a hose with a nozzle on it-- it impedes flow, but increases velocity and effective force. So I think a very large funnel is a sign that jetting is slow and leisurely, but I suspect "very large" is in relation to other factors (total mantle respiratory volume, mantle contraction speed, ability to close the intake part under pressure, how much the funnel can contract to make its aperture narrower, etc.) that I don't know how to quantify.
     
  7. OB

    OB Colossal Squid Staff Member Moderator

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    I follow your argument and agree. If only, because it supports my own theory :wink:
     
  8. OB

    OB Colossal Squid Staff Member Moderator

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    Another aspect to take into account: compared to A. dux, M. hamiltoni has relatively small gills, oriented vertically (dorso ventrally), rather than horizontally (rostro caudaly), making a counterflow gass exchange less efficient.

    In all suggesting a lesser metabolic rate.

    Maybe fins beat jet propulsion hands down for metabolic economics?
     

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