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Eyes as large as dinner plates

OB

Colossal Squid
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Yes indeed, but what do they see, our friends messie and archi? It is, to all intents and purposes, pitch black at hunting depth. Do they look for disturbances causing bioluminescence? They don't seem to prefer prey which has its own photophores... I recall one Architeuthis specimen being hauled in by fishermen, after they detected a large object on their sonar, hovering 5 meters over a school of hoki at an angle of about 45 degrees. Even if our squid overlords merely respond to fish swimming haphazardly into their clubs, they still need to know where to go in the first place. I now turn to the experts, is there any light left at 600-900 meters below? I was always taught that sunlight will not penetrate past 300 meters below sea level. I also know, however, that i.e. hatchet fish still employ countershading (reinforced by blue bioluminescence!), even at that depth.... I'm all confused now :confused:

For certain, the recently photographed Architeuthis specimen had a strobe at its disposal.

On a secondary note, do we know whether Architeuthis hunts both by day and by night? What do bycatch figures teach us there?
 

Feelers

Vampyroteuthis
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I have often wondered the same thing - instead of no eyes they have massive ones. Is there that much bio-luminescence down there?
What do they see? Endless darkness? Graven images? It's all very confusing.
 

OB

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Well, there is a lot of bioluminescence down there, and, in all fairness, the less there is, the bigger eyes you need.
 

monty

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ob said:
Yes indeed, but what do they see, our friends messie and archi? It is, to all intents and purposes, pitch black at hunting depth. Do they look for disturbances causing bioluminescence? They don't seem to prefer prey which has its own photophores... I recall one Architeuthis specimen being hauled in by fishermen, after they detected a large object on their sonar, hovering 5 meters over a school of hoki at an angle of about 45 degrees. Even if our squid overlords merely respond to fish swimming haphazardly into their clubs, they still need to know where to go in the first place. I now turn to the experts, is there any light left at 600-900 meters below? I was always taught that sunlight will not penetrate past 300 meters below sea level. I also know, however, that i.e. hatchet fish still employ countershading (reinforced by blue bioluminescence!), even at that depth.... I'm all confused now :confused:

For certain, the recently photographed Architeuthis specimen had a strobe at its disposal.

On a secondary note, do we know whether Architeuthis hunts both by day and by night? What do bycatch figures teach us there?

There's some interesting discussion of Architeuthis vision thoughts in this thread:

http://www.tonmo.com/community/index.php?threads/3926/

In particular, um... posted a wonderful reference on vision in the deep sea that discusses the intensity and nature of light at various depths, and a lot of biological issues about vision:

http://www.tonmo.com/community/index.php?threads/3926/#post-57691

good stuff!
 

Feelers

Vampyroteuthis
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I dont really understand the theory of bioluminescence - I understand small amounts such as the masking silhouettes from above, but I dont get how smaller organisms benefit from bright obvious bioluminescence. They can use it to attract food, but wouldnt this be just as or even more likely to attract predators? It seems like your dammed if you do and dammed if you dont!!

If archyteuthis' eyes can't see any light from above then its diet would presumably consit of only bioluminescent organisms. Is this the case? I have no idea.


How much light is at those depths? Is it 100% totally dark? or is there enough to be used for hunting?
 

Jean

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Feelers said:
I dont really understand the theory of bioluminescence - I understand small amounts such as the masking silhouettes from above, but I dont get how smaller organisms benefit from bright obvious bioluminescence. They can use it to attract food, but wouldnt this be just as or even more likely to attract predators? It seems like your dammed if you do and dammed if you dont!!

If archyteuthis' eyes can't see any light from above then its diet would presumably consit of only bioluminescent organisms. Is this the case? I have no idea.


How much light is at those depths? Is it 100% totally dark? or is there enough to be used for hunting?


Many of them use species specific patterns probably for mate recognition (eg Lanternfish) others use it to attract dinner (eg anglerfish) some clever ones even have red coloured filters which turns the light they emit red which negates the protective red colouration that many deep water organisms have! Tis an area of study all on it's own!!!

J
 

OB

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Feelers said:
If archyteuthis' eyes can't see any light from above then its diet would presumably consit of only bioluminescent organisms. Is this the case? I have no idea.

The staple food of Architeuthis is considered to be both benthopelagic (Nephrops, Eledone, macrourid fishes, possibly the orange roughy) and pelagic ( onychoteuthid, histioteuthid and ommastrephid squids, Trachurus, Micromesistius) and includes fast-swimming fish and squids.

Hoki, the prey that keeps SOS' population occupied, don't "do" photophores, nor do patagonian toothfish, that in turn keep a vast population of Mesonychoteuthis happy.

In order to detect prey, or prevent predation for that matter, under (assumed) zero light conditions, you'd need either sensitive motion sensors (i.e. lateral line in fish) or look for bioluminescence as a result of non-bioluminescent prey disturbing plankton in turn. You'll notice when studying deep water fish, that development of the lateral line in these is excellent. I'm not aware of squid having a similar system at their disposal...
 

Jean

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ob said:
In order to detect prey, or prevent predation for that matter, under (assumed) zero light conditions, you'd need either sensitive motion sensors (i.e. lateral line in fish) or look for bioluminescence as a result of non-bioluminescent prey disturbing plankton in turn. You'll notice when studying deep water fish, that development of the lateral line in these is excellent. I'm not aware of squid having a similar system at their disposal...

Tis possible tho' Bernd Budelmann reported on what appeared to be a similar system on the head and tentacles of cuttlefish

Budelmann BU, Bleckmann H. 1988. A lateral line analogue in cephalopods:
... Trans. R. Soc. Lond. B. 315:305–343.

Sorry can't remember the rest of the title!

It's moot point whether or not it exists in the Messies and Archies but I guess it is possible!

J
 

Feelers

Vampyroteuthis
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Just read up about the lateral line thing, very interesting.

So much of the plankton down there is bioluminescent too? I remember being told ( at school) that there wasnt really any plankton below 10m!!
 

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