When I first heard this I immediately thought of some kind of filter
feeding marine organism (like John's clam) doings its business, and the
one that strikes me most is a lugworm (Arenicola marina), on European
shorelines they can occur in millions, especially if the sand is a bit
muddy with organic material, we can usually only find them at low tide
when you can see the casts from their burrows:
I quote: http://en.wikipedia.org/wiki/Lugworm
<http://en.wikipedia.org/wiki/Lugworm>
"A lugworm lives in a U-shaped burrow in sand. The U is made of an
L-shaped gallery lined with mucus, from the toe of which a vertical
unlined shaft runs up to the surface. This is a head shaft. At the
surface the head shaft is marked by a small saucer-shaped depression.The
tail shaft, 2-3 inches from it, is marked by a highly coiled cast of
sand. The lugworm lies in this burrow with its head at the base of the
head shaft, swallowing sand from time to time. This makes the column of
sand drop slightly, so there is a periodic sinking of the sand in the
saucer-shaped depression. When it first digs its burrow the lugworm
softens the sand in its head up into the head shaft by pushing its head
up into it with a piston action. After that it is kept loose by a
current of water driven through the burrow from the hind end, by the
waves of contraction passing along its body. It weighs 2-5 oz. Lugworms
also have groups of hair on the outside of their bodies that act as
external gills. This can rapidly increase its uptake of oxygen"
and here is a nice description and diagram:
http://www.glaucus.org.uk/lugs.htm <http://www.glaucus.org.uk/lugs.htm>
I am not a marine biologist but I could imagine you accidentally
planting one of your hydrophones next to a lugworm burrow and picking up
the sound of it rhythmically pulsating sand/ water through its body.
Maybe look for the casts at low tide and see if you can record it again
- not sure if they feed at low tide though.....that's the wild creature
theory from a simple biologist !
Chris
www.wildechoes.org <http://wildechoes.org>
--- In "hartogj" <>
wrote:
>
> Hi Marinos,
> Searching the web a bit,I found that Crete had the earliest known
modern bathroom with a flush toilet around 1500 BC. This is not off
topic for our group, because back then that was still considered nature
sound:) They also had elaborate piped drainage systems for quite some
time before that. Many of those old systems are still in use, so who
knows what might be hidden below the sand. My official guess though, is
it is a clam.
>
> John Hartog
>
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