Hi Maurizio,

Yes, you caught some of the same errors in what I thought
I observed that Lynn Scheu pointed out, based on the anatomy
of Oliva (versus Olivella, etc).  What I took to be the stomach
of the O. miniacea was surely the pouch, which it rapidly
stuffed with the living Strombus gibberulus.  I intended to write
a follow-up to the message, but never got around to writing it.

In the following week, the Oliva would chase, and catch, the
Strombus gibberulus.  At one time, the Oliva had caught all
three of the small Strombus.  However, a day later they were
all three back on top of the gravel, hopping around as if nothing
ever happened.  Over a period of a few days, the Oliva did
succeed in catching and eating one of the S. gibberulus, then
another, and finally the last one.  It appeared that the Oliva
must have caught the strombs 4 or 5 times each before it
finally managed to kill them.  How it extracted the animal
from the shell I don't know.  It did seem apparent that whatever
method the Oliva used to kill the strombs was not immediately
effective, maybe because the S. gibberulus are so active and
"kick" when they are captured.  Given enough opportunities,
the Oliva's strategy was effective, though, whether by paralysis
or suffocation, or some other means.

It was interesting to me that the O. miniacea also attempted
to capture the Strombus luhuanus, which was considerably
larger than the olive.  This was certainly not a "touch" reflex,
because the Oliva encountered several Conus canonicus that
were smaller than the S. luhuanus, and made no attempt at
eating them.  It seemed to recognize Strombus as proper
prey, whether by "scent" or some other method of recognition.
Regardless what the previous observations were of poor sense
of smell and difficulty in locating food (in the Florida species),
I repeatedly saw the Oliva miniacea pursuing the Strombus
around the tank until it caught one.  It didn't appear to be wan-
dering, but deliberately following the trail of the mollusc it was
after, and in high-speed pursuit.  Maybe it could "see" the
S. gibberulus it was chasing?

By the way, Lynn Miniacea didn't survive the month.  Although
the cones definitely don't prefer Oliva, if the small Cypraea
and Cymatium are all gone, they will eventually eat Oliva.  The
only thing apparently more distasteful to Conus textile is
Pterygia nucea -- I have had one in the tank now for eight
months, and nothing will touch it, no matter how hungry the
cones are.

I also postulated in the Cone Wars that Conus canonicus sur-
vived by "staying out of the way" of Art and Paul Textile.  Not
so.  They encounter each other often, and the Conus textile
obviously either think they are "brothers," or they don't consider
them competitors, just as they don't bother the non-competing
Conus striatus that are in the tank.  Contrast this with the short
life expectancy of any Conus episcopatus, C. bandanus, or C.
omaria that has been introduced to the aquarium.  Eduardo
Magnificus was never bothered by the C. textile, either, but
I didn't get to see if they would coexist in the long term due to
his fatal encounter with the Conus bandanus.

Cheers,



Don


----------
> From: Maurizio A. PERINI <[log in to unmask]>
> To: [log in to unmask]
> Subject: Oliva miniacea feeding behavior: considerations.
> Date: Tuesday, May 02, 2000 8:29 PM
>
> Tuesday   May 2, 2000   07:36 PM
>
> Dear Friends,
>
> I have recently had the opportunity to review Don Barclay's
> most entertaining observations regarding the feeding behavior
> of Oliva miniacea (Cone Wars II--Killer Olives; October 26,
> 1999). I do note, however, some apparent discrepancies
> between Don's descriptions as compared with my own field
> observations, especially as they pertain to olive antomy.
> My particular purpose here is to attempt to differentiate between
> the species' feeding behavior according to the state of the
> intended food item : dead or alive.
> The olives have a long and very flexible proboscis , at the tip
> of which is located the buccal mass. This attribute is considered
> to be highly evolved anatomical feature, because it allows the
> radula to operate in the enviroment. (In comparison, the olivella's
> buccal mass is located at the base of the proboscis).
> During a recent field trip to the Philippines, I was able to observe
> a juvenile specimen of Oliva sp. ( 2cm in length) while it was
> feeding :
> a) It rolled over onto its right side;
> b) It extended its proboscis (which looked very much like the tube
> of a Hoover vacuum cleaner !!) as far as the pouch of its foot. Some
> bits of food were clearly visible, due to the transparency of the wall
> of the pouch;
> c) It then began to eat using its radula, with its odontophore slowly
> and rhytmically pulsating.
> It is believed that the proboscis was evolved from the anteriorest
> portion of the esophagus. At the base of the anterior esophagus
> and above the posterior esophagus lies a "nervous ring"; this ring
> surely prevents the passage of large morsels directly into the
> stomach. Accordingly, all food must be separated into small pieces
> by the radula (or, at least, partially dissolved) before it can be
> swallowed. Due to these anatomical considerations and in light of
> my own observations, I think that something is amiss in Don's
> description (or that he was not able to witness the entire feeding
> sequence). I believe that all the food must go into the pouch before
> it can be actually consumed. Many among us know that the olives
> handle their dead food with their propodium, cover it with mucous,
> and then insert it into the their pouch. But what happens when the
> food item is living prey, as it was with Lynn and the hapless Strombus
> gibberulus ?
> Every predation (usually) involves two salient elements : the capture
> and the kill. From Don's description, we know that O.miniacea lifted
> up the srtombus (as I understand, using its propodium to do so) and
> then immediately swallowed it into its proboscis. ( In Don's words,
> "like a snake that has eaten an egg". )  We must assume that the
> capture was made by use of the propodium, but why did O.miniacea
> use its proboscis if the large prey (and especially its shell) could not
> possibly pass the nervous ring and go directly into the stomach ?
> My thought is that the olive used its proboscis only to kill the strombus.
> ( Did Lynn smother the prey to death ? Or poison it by a gland's unknow
> secretion ? ) Afterward, when the O.miniacea was burried in the sand,
> the prey was regurgitated, covered by mucous, and inserted safely
> into the pouch for later consumption.
> There is only a problem: How does the olive take out the flesh from
> the shell ?
>
> My dear friends, and especially Don, what are your thoughts about
> my theory ?
>
> Kindest regards to all, Maurizio.