Shell Carrying Cephalopods: Defensive Tool Use or Protective Nest Guarding?

Friday, January 22, 2010 at 11:55 AM Bookmark and Share
There's a post over at Jerry Coyne's blog (WEIT) pointing to another video of an octopus using tools for defense.  In this case, the individual (a veined octopus) used 3 shells, then once alarmed carried them off holding them underneath it's body.  While not all that unexpected for this species given their use of shells and such for shelter, the observation follows the recent story of such tool use as a first among invertebrates as published in the journal Current Biology [1] (more on that story on the blogs WEIT and Not Exactly Rocket Science or go here for the journal article and here for comments).

But are we missing something in these videos?? Here's the latest video, as featured on the Current Biology website:


Here's the first video (a supplement to the paper mentioned above) of an individual using coconuts:


The use of shells or coconuts as protective tools is noteworthy, but there might be more to the story than that. I once observed a small octopus inside 2 clam shells in the north eastern part of the Sea of Cortez, and while I didn't observe any of the carrying behavior documented in these videos, there was one additional detail I have yet to see mentioned in these discussions: the shells were lined with octopus eggs.

While I had wondered about my own observation upon first seeing the coconut video, I saw no eggs or behavior to suggest there were eggs present. This time, however, could be different. Here's a still from the video above showing what could be eggs in one of the shells:


If you haven't seen octopus eggs before, here's a closer image pulled from the web

So am I seeing things, or are these eggs? If so, is this not worth mentioning or has it simply gone unnoticed until now?

While perhaps a small detail, if these are indeed eggs in the shells it is important to recognize this fact.  Tool use alone may be a noteworthy observation, but such observations are most valuable when matched with our best description of the context in which the behavior takes place.

References:

  1. Finn, Tregenza and Norman. Defensive tool use in a coconut-carrying octopus. Current Biology, Volume 19, Issue 23, R1069-R1070, 15 December 2009. doi:10.1016/j.cub.2009.10.052

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