Mesonychoteuthis eyes vs. Architeuthis

tonmo

Titanites
Staff member
Webmaster
Moderator
#1
Who is the indisputable leader in eye-size?

Someone visited the ZPi Cephalopod News page and posed this question in response to the many articles that made reference to the colossal squid's "dinner plate"-sized eyes. More information can be read on the site itself.

I was exchanging emails with the guy who maintains that site and he was curious if any clarity could be lent here. I let him know that the two of you (Steve and Kat) are out carousing and whatnot, but promised to pose the question here... it's a valid one! As always, all input from the community is welcomed. Thanks in advance,

-- tonmo
 

Steve O'Shea

Colossal Squid
Supporter
#2
Howdo T, all. This is a message that I sent through via email in response to this query.
.........
Hi. It is the beak that I am examining in that picture.

The specimen (Mesonychoteuthis) is the largest thus far known of this species, but was extensively damaged (it was in 3 pieces and has been reassembled in the picture). Both eyes were destroyed at capture, so no better images exist (for this specimen). What did exist were fragments of the eyes, the sockets into which they were positioned in the cranium, and several pieces of tissue with the ventral photophore (crescentric). They were of a significant size.

The 1981 Russian image reproduced in Ellis's book is of an animal lying on its dorsal surface. What is visible is the funnel and two large, partially obscured bulges either side of the arm crown (at the base). These large bulges are the eyes. Having seen in excess of 105 Architeuthis specimens I can assure you that the eyes of Mesonychoteuthis are larger than anything known for Architeuthis. I can also assure you, based on the size of beaks recovered from sperm whale stomach contents (with lower beak rostral lengths [LRL] reaching 48 mm) (our recently reported 2.5 metre mantle length specimen [with a 37mm LRL]), that the animal in the picture nowhere approaches the maximum size that this animal attains, and that it is smaller than the specimen that we recently reported.

Over the past 8 years we have done everything we can to reduce the reported lengths and weights of Architeuthis, not exaggerate them. Similarly, when this specimen of Mesonychoteuthis was first brought to our attention we expected that it too had been exaggerated. When examining it we expected it to be fully mature, we expected the beaks to be as large as (or very close to in terms of size) those reported from stomach contents of sperm whales. We were amazed that they were not. If this animal does attain a mantle length between 4 and 5 metres then it truly is one most formidable monster; it was frightening enough at 2.5 metres!

With kindest regards
Steve O'Shea
 

tonmo

Titanites
Staff member
Webmaster
Moderator
#3
Having seen in excess of 105 Architeuthis specimens I can assure you that the eyes of Mesonychoteuthis are larger than anything known for Architeuthis.
I somehow missed this response the first time around...

That's pretty sensational stuff in and of itself! That is, you are strongly suggesting that the Colossal Squid has the largest eyes of any animal on earth, as opposed to the previously-thought Architeuthis.

I believe one of Ellis' books reported that an Architeuthis eye could grow to be as large as 16 inches in diameter. Is it your estimation that this was not an accurate report (exaggerated somewhere down the line), or do you feel it is accurate, yet smaller than what a Mesonychoteuthis eye can reach?
 

Steve O'Shea

Colossal Squid
Supporter
#5
I've just been playing around with our bucket-sized Mesonychoteuthis specimen and taken a few pictures of the head and eyes. This specimen has the largest eye lens of any squid I've encountered!! Really quite unusual - it must be doing something pretty special.

The entire head is made up of the two eyes; I'm afraid when dealing with preserved specimens that everything looks a little horrible, and it does require you to use your imagination to reconstruct what the live-animal would look like, but here goes .....



 

tonmo

Titanites
Staff member
Webmaster
Moderator
#8
Definitely a big eye socket there... can you measure the diameter?
 

Clem

Architeuthis
Supporter
Registered
#9
Steve,

Allowing for the effects of gravity and general deadness, it appears that the eye-socket of a live Colossal would still be somewhat less than round. Does this suggest to you anything about the animal's physical orientation?

Is the spherical orange bit the lens? Did it shrink, much?

Clem
 

Steve O'Shea

Colossal Squid
Supporter
#10
Clem said:
Steve,

Allowing for the effects of gravity and general deadness, it appears that the eye-socket of a live Colossal would still be somewhat less than round. Does this suggest to you anything about the animal's physical orientation?

Is the spherical orange bit the lens? Did it shrink, much?

Clem
Yup, the spherical orange bit is the lens. I'm afraid we need better specimens to figure out what is happening with the eyes and their orientation. I'll just have to work harder to procure this material .....

The relative lengths of the arms will (ok, should .... a little theory we're developing here) tell us something about the animals orientation (at least of the arms). I'm afraid I need to secure/procure a lot of comparative material to get to the bottom of all of this, but there certainly is an interesting story to be told.

That lens is huge by squid standards; I don't think it has shrunken (is this a word?). Beats 'shrunked' - my brain has shrunked for sure.
 

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