BREAKING NEWS: Sleeper sharks as predators of giant squid

Steve O'Shea

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Emperor said:
You could imagine a current carrying dead squid carcasses into colder waters where the squid might sink to the bottom.
Ja.... magnificent! I can imagine this - a colossal graveyard, where all of the spent, ill and dead individuals gather and get picked off/eaten by the seadog scavenging whales and shark.

Even a sperm whale with grossly deformed/damaged jaw lives, eats and survives .... so maybe this big brute bull whale is doing no more than scavenging on the seafloor in this Colossal Graveyard. The scars on the hides of the whales could then become scars caused by live Colossal Squid attacking the whale (and the whale was lucky to survive!!!).

Ja ... it all makes sense now :biggrin2:

:heee:
 

jmccor

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MuscaDomestica said:
Don't the sleeper sharks also have a copepod that lives in one of their eyes, effectively making them blind?
Greenland shark (Somniosus microcephalus) has been posited as the predator off Sable Island (off Nova Scotia) that has been leaving a modest carpet of dead harp/grey seals on the beaches ... with eerie spiral strips of flesh torn off their bodies. A documentary on Cdn TV showed the seals swimming around the sharks (major parasites tangling off both shark eyes) and, again, it's hypothesized that the parasites act like a lure ... the seal investigates ... BAD idea ... the shark grabs a flipper ... voila. Spiral skin tear avec blubber.

Picture of wound 2/3 down on this page:
http://www.conservationinstitute.org/sharkattacks.htm

Major researcher involved is Zoe Lucas.

James McC.
 

um...

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Phil said:
...if Architeuthis body tissues are saturated with ammonia keeping the animal buoyant, following death would one expect the carcass to rise to the surface, remain floating at depth with a neutral buoyancy before breaking up, or sink to the bottom? Without propulsive power from the fins would the dead animal rise like a cork in a bottle or do the ammonia ions keep it perfectly in balance, as I suspect?
Now there's a topic that could use its own thread in the Physiology and Biology forum.

My (probably weak) assumption would be that the squid would 'prefer' to maintain slight negative buoyancy, or at least to err on the side of negative buoyancy. If this information is correct, and I see no reason to doubt that it is, then Architeuthis spends a lot of its time with its funnel pointing downwards. Since the beast has to breathe, I figure that it would make sense to at least have the option of utilizing the exhalation current to offset any sinking which might occur. Or, stated a bit differently, it might make sense to have negative buoyancy to offset any upward momentum caused by exhalation. (Unless the squid sits 'upside-down' in the water and bends the funnel upwards...) I wonder: How 'softly' can the squid breathe, and how much commotion would arise from relying primarily on the fins to maintain depth? Being positively buoyant seems a bit detrimental in terms of stealth and energy efficiency. Also, I'd expect that 'down' is probably a safer direction to go than 'up' into brighter, warmer water. It seems that it would be harder to breathe, harder to hunt, and easier to get eaten up there.

However, at least some dead Architeuthis do float to the surface. This leads me to think that I might be speaking out of the wrong end of my digestive tract again.

Here's a few other questions that have just popped into my head:

Would there be much of a change in buoyancy after an egg mass is released? Without really thinking about it, I would presume that such an event would slightly increase the density of the squid.

Does the ammonium chloride solution in an Archi's tissues have a different coefficient of thermal expansion than seawater?

Do we have any idea at all what mechanism might be involved in regulating the concentration of ammonium chloride in the squid's tissues? How finely and rapidly can the concentration be tuned (assuming that it even can be)?

:sleeping:

:archi: :confused:
 

Phil

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Great post um..., I see where you are coming from. Here's another question to add to your list...

Does the salinity of the seawater affect the bouyancy of squid? I wonder if the latitude and the relative salinity of the seawater has any effect on whether an Archi floats or sinks? Are comparative levels of salt content of seawater a common factor with Archi strandings?
 

um...

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I'm almost positive that it does/is. That's what got me thinking about how well the squid might be able to adjust the concentration of ammonium chloride to account for the changes in ambient density that it will invariably encounter. Now, I would assume that an Archi who's pushing up the plankton (:notworth:) is no longer capable of adjusting its buoyancy very quickly at all and, upon drifting into denser water (if it even gets the chance), will float up to the surface.

Another thought: Since the arms and tentacles are probably more tasty and easier to eat than the rest of the carcass, I would expect them to be nipped off more quickly by scavengers. Since they're also less buoyant than the rest of the body (on average), it would follow that their removal would cause the remainder of the squid to rise to the surface (if it was near enough to neutral buoyancy to begin with).


What effect does decay have on buoyancy?

Is upwelling any sort of a factor here?
 

mikeconstable

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Thoughts?

When ammoniacal squid die, the ion channels that maintain the inbalance of internal/external ions would stop working (but not necessarily quickly?)
So ammonia would diffuse out, and sodium in, making the carcase increase in density.
Steve O'Shea says these creatures make everything stink - do they also have high concentrations of organic amines (which are also likely to be water-soluble, and degrade to ammonim salts)?
 

um...

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um... said:
...how much commotion would arise from relying primarily on the fins to maintain depth?
Probably not much. We're talking about a buoyant force of just a few pounds (sorry, a couple dozen Newtons) here, right?

Also, density changes in seawater are generally just a few parts per thousand, aren't they?
 

ika-san

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On the question of a lack of skin markings on the sleeper sharks raised earlier in the thread...

Assuming, as we are, that struggle marks seen on whales are scar tissue from squid attacks, when the squid tentacles and/or arms get a good purchase on the skin. Whale skin is relatively smooth and flat and, I would think, does not resist the toothy edges of squid suckers.

Having felt skin samples from some shark species, I recall it being somewhat rough to the touch, almost like a cat's tongue. I think the squid tentacle and arm "teeth" may have some difficulty getting any sort of hold on a shark. No hold, no mark and no scar. Sound plausible?

Does anyone know if the sleeper shark's skin has a similar texture to that of other sharks?

- Ika-san

PS Perhaps I hould consult "TSDNMO" - The Shark Dermatologist's News Magazine Online... :jester:
 

Clem

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ika-san said:
I think the squid tentacle and arm "teeth" may have some difficulty getting any sort of hold on a shark. No hold, no mark and no scar. Sound plausible?
ika-san,

Check out the photos below of a Greenland shark, Somniosus microcephalus. This sleeper's battered skin actually looks a lot like a sperm whale's, with an especially big transverse scar atop its head. (You can also see a copepod fastened to the shark's cloudy left eye.)



What really caught my eye was the circular scar visible on the shark's flank, below the first dorsal fin. My first thought was that it might be the mark of some parasitic fish which rasped or bit out a plug of flesh, but then the scar ought to be a solid, light colored infill of new tissue; this mark is a circular line. It does look a lot like the marks left by giant squid on Physeter. Maybe they ain't so tough?

Somniosus microcephalus has been documented in one of Architeuthis's known haunts, Trondheimsfjord, Norway. Click here to see a local example.

:?:

Clem
 

aron hills

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This topic has even made it into the latest edition of 'New Scientist' (No 2434 - 14th Feb 2004). It really does just repeat what we already know, but at least it is raising the topic with the wider scientific community.

FACINATING STUFF.

:whalevsa:
 

Sordes

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Sperm whales are very very massive animals, but in relation to their size, they have very thin skin, and this skin isn´t very hard too, as the many scars of squid suckers and teeth on the bodies of bulls show. But sharks have very thick and hard skin, all, including sleeper sharks, and all have small teeth on the surface of the skin, which makes them not only faster, but also better protected against attacks. I have still the remains of a sharks skin from a shark-steak I ate. The steak belonged to an animal which was surely not longer than 2m, but the skin was about 5mm thick (it was probably a female, because they have thicker skin) and very hard, I had even problem to cut it with a sharp knife. In this case I don´t wonder why sharks show no sucker markings on their skin. Sleeper sharks can grow very large, about as large or perhaps even larger than great whites, although their size is often exagerated in the popular press. A specimen of 5m would have an armour-like skin of nearly 2cm thickness.
Sleeper sharks are often said to be inactive scavengers, but in fact this animals also hunt actively. It would also be strange if such large animals could always find enough carrion. They hunt no only fish and squid, but also often seals, and greenland sharks were even found with whole rendeers in their stomaches, they probably killed when a herd did swim in a fjord or between isles.
 

chrono_war01

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I was wondering if you could build a machine like in the ones in "Animal Face-off" from Discovery Channel that emulates the effectiveness of a Messie's arms, hooks and beak on a piece of shark skin.
Sleeper Shark vs. Messie, anyone?
 

main_board

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Sordes said:
Sleeper sharks are often said to be inactive scavengers, but in fact this animals also hunt actively. It would also be strange if such large animals could always find enough carrion. They hunt no only fish and squid, but also often seals, and greenland sharks were even found with whole rendeers in their stomaches, they probably killed when a herd did swim in a fjord or between isles.
Or, again, fed on a reindeer that drowned during the crossing and sank to the bottom where the sharks are found. They might not need a whole lot of food either. They are generally leisurely swimmers, live in cold waters, grow slowly, etc. It might be that they have evolved to need little food as a result of scavenging. Also, many repiltes only eat once every week or two (snakes, crocs, etc.). Just cause its a big animal doesn't mean that it needs a lot of food. Though that would make sweet footage of a sleeper shark attacking a herd of reindeer, I'll wait until I see it to believe it.

Excellent posts and interesting thread!
Cheers!
 

Sordes

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I had also the same idea. But greenland sharks are relatively often caught only some metres under the surface, and a large greenland shark would surely use the opportunity to catch a swimming rendeer, and I also read that they even swim sometimes in very shallow water in the fjords, near the mouths of rivers. So it could imagine that they sometimes really attack swimming rendeer (and undoubtly eat also drown ones).
Although sleeper and greenland sharks have a very slow metabolism, I really doubt that they feed only on carrion.
 

OB

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Greenland sharks can sometimes themselves become carrion, a feast for a well known scavenger species at that... hmmmm :biggrin2:
 

chrono_war01

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I'll have the shark steak, but hold the ammonia.
 

Infusoria

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"Although the sleeper shark may be the most spectacular individual shark surveyed, I gotta say, the lantern shark is just as interesting. The ventral surface of this small shark is luminescent, which has led some to speculate that this schooling animal uses light to maintain cohesive formations in the lightless, benthic realm. These schools should also be capable of killing prey items much larger then the individual sharks (which average less than 18 inches in length). (I think schooling attacks on Mesonychoteuthis may have been proposed by some smart person over in the “Colossal Squid Necroscopy” thread.)"

I've been looking at the gut contents of some lantern sharks recently and they have mostly contained bits of prey, not whole animals. Only discovered this thread today, it's very interesting.
 

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