Octopuses are cephalopods, which have separate anal and oral openings. Indeed, descriptions of the cephalopod GI tract clearly depict an anal opening.

However, I am very confused about how this applies to the octopus. I don't think I've ever seen the anus depicted - where is it? What does it look like? Does anything much come out?

My first instinct would be to simply do a google image search for this. Unfortunately, those results are flooded with unrelated hits (apparently the octopus is a popular motif for tattoos... in a certain part of the body).


The anus of Octopus is channeled into its siphon. enter image description here Image taken from Carina M. Gsottbauer


Siphon is a tube that leads from the mantle to the outside. Octopuses use their siphon to force water out in jets for propulsion and to flush waste products from the anus.

From Encyclopedia of the Aquatic World, Volume 6 By Marshall Cavendish Corporation

  • 11
    $\begingroup$ And here I was thinking that the siphon just ejects clean, harmless water... I'll keep this in mind next time I encounter an octopus! $\endgroup$ – Superbest Aug 16 '16 at 20:57
  • 5
    $\begingroup$ I would imagine that you'd probably have to worry more about that poison gland than the highly-diluted waste that is ejected from the siphon. $\endgroup$ – Robert Harvey Aug 16 '16 at 21:22
  • $\begingroup$ @RobertHarvey Isn't the poison of Octopus injected through a bite? thecephalopodpage.org/octobite.php $\endgroup$ – Tyto alba Aug 17 '16 at 6:10
  • 2
    $\begingroup$ @SanjuktaGhosh please add citations to your answer on where the image and quote originated. If you use images and/or text that are not your own words, you need to cite the sources. $\endgroup$ – MattDMo Aug 17 '16 at 16:24

protected by Chris Dec 9 '17 at 13:52

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.