Message
Rosemary,
This happened several years ago and I can't recall his
name. I can recall his image but not his name. I'll contact my
"X". Perhaps she can recall. When either of us remembers, I'll try
to contact him and test HIS memory.
If I lived near the Gulf, I might collect some
shells and take them to a shallow, fairly fast moving and (most important)
'gator -free stream. I'd drop a shell in to see whether the
current was fast enough to make it spin at all. If so, then I'd drop
them in one at a time, outside-down. Record it's length, whether it is a
right or left valve and whether it spun clockwise, counterclockwise, both or
neither. Then, retrieve the shell and try it once or twice more before
testing the next shell.
Come
to think of it, we do have thundering herds of Clinocardium nutalli here.
There's no shortage of streams nor rain to make them move. Maybe I can do
this myself!
Any chance of gettng hold of a copy of the
paper? Was it ever published? I've come across this suggested
explanation before, but haven't come across details of any experimental
test - sounds interesting.
Bas
----- Original Message -----
Sent: Monday, January 23, 2006 8:02
PM
Subject: Re: FW: Re: Effects of
collecting shells from beaches, and change s in the numbers of shells on
beaches
For whatever this is worth....
Some years ago, I noticed that 23 of 25 cockle shells my
kids gathered from Casey Key beach were, I believe the left valves. I
mentioned this to one of my co-workers nad he said that he had done a short
paper on that phenomennon while an undergraduate. The jist was that the
valves spin in opposite directions when caught up in an alongshore
current. He painted several of them, dropped them in the "first trench"
and spent a few days watching them. Very soon, half of them would
disappear into deeper water while the others remained. When the tide
changed, the direction of the current reversed and the effect was the same -
but the valves that remained in the first scenario spun into deeper water
while the others remained.
I've often wondered whether the ratio changes from summer
to winter - assuming that the alongshore di8rection
changes.