Octopus with branching arms


Staff member
Moderator (Staff)
Nov 19, 2002
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.


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


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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.'

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?

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

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