Octopus with branching arms

Tintenfisch

Architeuthis
Staff member
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#1
What would you do if you came across one of these??

Just a weird mutation that apparently pops up sometimes... anyone else come across images or reports of this? The one I know of best is from Sasaki (1929), from which I have included the photo and a bit of text. He also refers to two other reports, so I'll give the refs below.

Ikeda, S. 1800-1891. A list of Japanese Cephalopoda in the Zoological Institute of Imperial University. Zoological Magazine of Tokyo II, III.

Sasaki, M., 1929. A monograph of the dibranchiate cephalopods of the Japanese and adjacent waters. Journal of the Faculty of Agriculture, Hokkaido Imperial University 20 (Supplement 10): 357 pp.

Smith, E.A. 1900. Notes on an "Octopus" with Branching Arms. Annals and Magazine of Natural History 7(20): 407-411.

:cyclops:

[Edit - Re-attached the Sasaki figure (1929, Plate IV) in 2007, not sure what the other image was.]
 

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um...

Architeuthis
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#2
I've just redecorated this office in a sort of "Partially Digested Lunch" motif.

Kidding. That's really neat, :twisted:.
 

Tintenfisch

Architeuthis
Staff member
Moderator
#4
I know, kind of socks you in the gut the first time you see it, huh?
The Smith paper actually gives another reference:

'Furcation in the arms of Cephalopods appears to be a rare occurrence, judging from the few records of such abnormalities. C. Parona* has described and figured bifurcation in an arm of "Eledone moschata," an additional arm in E. Aldrovandi, and a bifurcate arm in "Octopus vulgaris." These are the only records I have been able to discover of such irregularities of growth.

*Boll. Mus. Zool. Anat. Comp. Genova, 1900 no. 96.'
 

Tintenfisch

Architeuthis
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#8
It's a photo. Smith gives a slightly more whimsical illustration but does appear to have been looking at the same phenomenon.
 

Phil

Colossal Squid
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Registered
#9
Kat,

What do you think could cause this deformity? Is it a random mutation do you think, or are there more sinister forces at work here?

Phil
 

Melissa

Larger Pacific Striped Octopus
Supporter
#10
Polydactyl octopus? Polydactypus? :cyclops: I don't know why this makes me happy. Do you think such an animal would lead a "normal" octo life? It doesn't look debilitated.

Melissa
 

Fujisawas Sake

Larger Pacific Striped Octopus
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#12
hmmm...

Odd yes, but not surprising. Polydactyly isn't THAT rare, though in cephs the result is very bizarre. I wonder how functional the branched limbs were?

John
 

andermuffins

Larval Mass
Registered
#14
I just happened to be browsing through the images on cephbase in preparation for giving a little cephalopod speech at school the other day and found an image of just this sort of thing, although it was only one branch on one arm.

Cephbase image search result

For those who don't have time for cephbase to load: The photo by John W. Forsythe shows a "bifurcated arm tip" on an Octopus briareus and further states that both tips were fully functional.

--
Mark in Berkeley
 

tonmo

Titanites
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#17
I had never read / seen of anything like this before today. Thanks for posting this T!!
 

Brown

Larval Mass
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#18
We see bifurcating arms once or twice a year and always in the larger (= older) animals (Octopus vulgaris). As we always see them on the tips of the arms (rather than being a whole extra arm (e.g. 9)) and we know the arms regrow after injury, I've always thought it represents what sometimes happens after regrowth rather than a mutation.. But I could be wrong. We also see the same thing sometimes in regenerating starfish arms. To my knowledge no one has made a special study of this.
 

Steve O'Shea

Colossal Squid
Supporter
#19
Here's a paper:
Toll, R.B.; Binger, L.C. 1991. Arm anomalies: cases of supernumerary development and bilateral agensis of arm pairs in Octopoda (Mollusca, Cephalopoda). Zoomorphology 110: 313-316.

The abstract goes as follows:
The first case of true hexapody among the Octopoda, resulting from bilateral agensis of one arm pair, is described for a male Pteroctopus tetracirrhus. A case of decapody, with uniform development of all arms, is also reported for the first time for a male Octopus briareus. Both conditions apparently result from developmental anomalies of the embryonic arm anlagen. A survey of other anomalous conditions relating to arm devlopment and regeneration within the Cephalopoda is provided. A possible relationship of polyfurcation of arm tips in the Octopoda with regenerative processes in amphibian limbs leading to similar conditions is suggested.

They cite the following papers:
Gleadall, I.G. 1989. An octopus with only seven arms: anatomical details. Journal of Molluscan Studies 55: 479-487.

Kumph, H.E. 1960. Arm abnormality in Octopus. Nature 185: 334-335.

Okada, Y.K. 1935. An octopus with branched arms and mode of branching. Annot. Zool. Japon. 15: 5-23.

Okada, Y.K. 1937. An occurence of branched arms in the decapod cephalopod, Sepia esculenta Hoyle. Annot. Zool. Japon. 17(1): 93-94.

Okada, Y.K. 1965a. On Japanese octopuses with branched arms, with special reference to their captures from 1884 to 1964. Proc. Jap. Acad. 41(7): 618-623.

Okada, Y.K. 1965b. Rule of arm-branching in Japanese octopuses with branched arms. Proc. Jap. Acad. 41(7): 624-629.

Palacio, F. 1973. On the double hectocotylisation of octopods. Nautilus 87(4): 99-102.

Robson, G.C. 1929. On a case of bilateral hectocotylisation in Octopus rugosus. Proceedings of the Zoological Society of London, 1929: 95-97.

Smith, E.A. 1907. Notes on an "Octopus" with branching arms. Ann. Mag. Natur. Hist. 7: 407-411.
..........
Sorry about the abbreviated reference citation for many; this is as is in Toll & Binger's paper; I can cite full details shortly (just need to check those Japanese ones out).

Cheers
O
 

um...

Architeuthis
Supporter
#20
Is it possible that the freak shown in the photo above was producing at least some of those furcations in response to non-arm-severing injuries?
 

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