Hi Roland,

Sorry to be late responding to your message, but have been
way behind on my e-mails.  Octopi will kill cone snails, and
sometimes they eat them.

A little over a year ago I had a small Octopus vulgaris in my
aquarium, and had the opportunity to watch it interact with
the cone shells that lived there.  It would often "wrap up" the
cones, and appeared to be trying to eat them, but was never
successful as far as I could tell.  However, when we tried
some experiments with a larger Octopus cyanea, it was a
different story.

We started with a plastic "kiddie" swimming pool, about six
feet wide and a foot deep, with coral rubble and some slabs
in the bottom and Astroturf around the edges to keep the
octopus from crawling out.  We then dragged an empty
Conus textile shell around the pool with a piece of fishing line,
hoping to see whether the octopus reacted to the pattern on
shell, recognizing it as a threat by sight (Conus textile venom
is deadly to an octopus).  The typical result was that the
octopus would extend one tentacle and push the shell away.
When a live Conus textile was introduced, the octopus
essentially froze--not moving away, but not pushing the live
snail away either.  The cone showed little or no interest in
the octopus, and crawled away.  When the cone was moved
back beside the octopus, the reaction was the same, but
after repeating this several times the octopus seemed to become
agitated, and finally pushed the snail away with its tentacle.

Since we hadn't had much of a reaction from the Conus
textile introduction, we tried the same thing with a Conus
striatus, a piscivorous cone whose venom isn't dangerous to
other molluscs.  The Octopus cyanea treated the C. striatus
much like he had treated the empty Conus textile shell, pushing
it away with a tentacle if it got too close.   Since it seemed to
be unconcerned about the Conus striatus, I put 5 others in
the pool, figuring they would meander safely around the pool
until I took them to Hopkins Marine Lab a couple of weeks
later.  Everything was fine for several days, but one morning
when I went to check on "Oscar" I found one of the cone
shells empty, and part of the animal floating on the surface,
with most of the foot eaten.  I also noticed that one of the
airstones I was using to aerate the pool appeared "fuzzy,"
and when I inspected it I found that the "fuzz" was about
fifteen Conus striatus teeth, all imbedded in the pumice.
Evidently the water movement alone was enough to prompt
the cones to fire their harpoons, no fishy smell required.

The next morning started the same way, with another cone
shell having been killed.  The animal had been completely
removed from the shell, but even less had been eaten
from this one than the one the previous day.  It made me
wonder if the octopus had killed the first one because it
was hungry (it had been eating crabs regularly) or if it had
been receiving the "airstone treatment," and was tired of
being stung by the cones.

That afternoon when I returned from snorkeling I added
several other Conus striatus to the pool, by now aware
that they might not all survive until I had the chance to
take them to Hopkins.   Turns out I was right.  The next
morning the pool surface was covered with slime and
pieces of Conus striatus animals, so many pieces in fact
that it looked like there must have been ten times as many
cones in the pool as there actually were.  Every cone in
the pool had been killed overnight by the octopus, each
one pulled from its shell and torn to bits.

I'll let you make your own guesses as to "why" Oscar
killed the cones.   But he was very effective at it in any
case, and didn't need to break the shell or drill it to
remove the animals.

As a footnote, I introduced a wide variety of molluscs
to the pool as potential food for the Octopus cyanea,
but the octopus would only occasionally kill one of them.
It definitely preferred crustaceans, and would only eat
molluscs if it had gone several days without being fed
crabs or shrimp.

Cheers,



Don



----- Original Message -----
From: "Roland Anderson" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Saturday, October 05, 2002 3:45 PM
Subject: cones and octopuses (or naticids)


> Hi all you shellers,
> I recently spent some time with a cone expert and the subject came up as
> to whether octopuses ever eat cone shells. Have you ever seen a drilled
> cone shell, either by an octopus or maybe by a naticid snail? I'm
> wondering if octopuses and maybe other drillers avoid cones because of
> their venom.
> Thanks in advance.
> Roland
>
> Roland C. Anderson, PhD
> Puget Sound Curator
> The Seattle Aquarium
> 1483 Alaskan Way
> Seattle, WA 98101 USA
> phone: 206-386-4359
>