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.