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Mystery cirrate octo

Joined
Feb 5, 2003
Messages
373
Hi everyone,

Very interesting thread. Noticed the 90, 100, and 140 increments on the fish board (agree with you Clem, with fisheries observers guaranteed to be cm's) and extrapolated some measurements. See attached.



Depending on what you take to be the posterior tip (I'd opted for green) there's some variation in ML but arm length and total length should be reasonable. I took the yellow line to be the end of the mantle, which is about the 101 mark. Appears a more exact limit in the other image posted.

I like Stauroteuthis gilchristi as an ID, but there are some real issues with proportions. Mainly, the head is way too big. For S. gilchristi mean ML/TL*100 = 15.94 +/- 2.09 (N = 8; fixed specimens; Collins and Henriques 2000). From the image, it's more like 28, 32, or 34 depending on your marks. While the its possible the arms could be made to lie straighter, which might increase the TL relative to the ML, I don't think it could make up for the difference. Can't comment on the different between fixed and fresh specimens.

Also, as T pointed out, there's all that gelatinous tissue. It looks like some is to be expected (also in Collins and Henriques 2000) but not to that degree. What I find interesting is that both of these are posterior oriented features, which to me supports the distortion by suction feeding of the toothfish. I mean, a fish that can engulf a critter this big without raking it with its teeth likely has a large mouth capable of generating plenty of suction.

Plusses: a TL of 50 cm fits expected size range, and the crazy cool colour is, apparently, appropriate. I've never handled this species, but I've worked with its Altantic cousin syrtensis a bit and I think this specimen certainly fits stauro morphology better than the other cirrate options.

Great photos! Hope there's more to come.
Cheers

Collins, M. A. and C. Henriques. 2000. A revision of the family Stauroteuthidae (Octopoda: Cirrata) with redescriptions of Stauroteuthis syrtensis and S. gilchristi. J. Mar. Biol. Ass. U.K., 80: 685-697.
 

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Clem

Architeuthis
Registered
Joined
Apr 6, 2003
Messages
1,839
Main_board, great job on the measurements. I didn't zero in on S. gilchristi until I'd received the second photo, which gives a better idea of the proportions of the armature relative to the body. The second photo seems to show roughly one third of the arms length, suggesting proportions appropriate for S. gilchristi, that is, if I'm correcting for angle of view and optical distortion as well as I hope I am.

Am I correct in thinking that this animal's chromatophores are on/in the superficial gelatinous layer? Could someone give me an idea of what the cross-section of the mantle tissue layers looks like?

I've been thinking about how this specimen was recovered. The preservation is so good that it can't have been in the toothfish's stomach for very long at all, which means that it had to have been gulped shortly before the toothfish took the baited hook. I'd ask hud2 about this, but does anyone here know what the hooks would be baited with? Perhaps the octopus was investigating or snacking on the bait when the fish snuck-up on it. Would've made for a major "D'oh!" moment for the toothfish.

Clem
 
Joined
Feb 5, 2003
Messages
373
Yeah, Clem, that the photographs are all angled initially drove me to measure out the specimen. To give a less biased impression of proportions.

From Collins and Henriques (2000), again, body gelatinous. Can't give more details as per a cross-section, but as far as colour goes, here's what they say: the area around the mouth is supposed to be darkly pigmented, pink or purple, which extends roughly 2/3 down the oral surface of the arms before lightening. Aborally, arms are transparent. The viscera are contained in a semi-enclosed pigmented membrane. The species has both a primary and secondary web, from which I believe most of the red colour is coming from on/around the arms (Google image 'Stauroteuthis'; in situ they're quite red). They later note that fresh specimens are quite different in appearance than fixed ones, and that when fresh much of the tissue is transparent and the eyes and viscera clearly visible. So, helpful? Haha.
 

Clem

Architeuthis
Registered
Joined
Apr 6, 2003
Messages
1,839
If the area around the buccal is darkly pigmented, then I wonder if the females show the sort of bright rings associated with your avatar. No need to deprecate with a "Haha." Always bear in mind that I don't really know what I'm doing.

Clem
 

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