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Off
Chub Cay, Bahamas, Day 3, 1999
With
great success finding Midas slitsnails, the team moves over shallower
seas ready to search for Adanson's slitsnail. Today Pat and Steven get
their chances to dive, along with Jerry and José. The sub dives to around
400 feet along a wall so steep it is sometimes undercut. What in the
world is a snail, or any other animal doing there if it can't swim or
isn't anchored to the wall? Yet there they are, one of the larger
snails, clinging to the wall. We find them dispersed, like Midas, one
and then another, ten or fifteen minutes apart. They are easier to spot
then Midas with their beautifully mottled garnet and ivory shells. The
shells are more pointed, and the spiraling cone shape more acutely angled
compared to Midas. They also differ in having a smaller muscular foot
that does not extend beyong the edge of the shell, and so is rarely
seen except
in aquaria.
As
the sub creeps along the wall a number of striking things appear. Overall
there is more visible life attached to the wall than at greater depths.
The wall is craggy, encrusted with sponges, isolated corals and lots
of fishes. There isn't the same build up of organic sediment at this
depth as we encountered at 2,500 feet. Undercuts in the wall prevent
sediment from accumulating. Adanson's slitsnails are not hard to spot,
just scarce, and a challenge to pick up because of their size, the vertical
wall, and the way they are sometimes wedged into nooks.
Although the team
spends six to seven hours each day collecting from the submersible,
long hours are also committed to lab work on the ship. The ship is equipped
with two labs, one wet and the other dry. All tanks are in the wet lab.
For the really deep water snails there is a cold-water tank. The rest
are kept in unchilled tanks. In
the tanks, a behavior peculiar to slitsnails is observed. When disturbed,
they exude a milky substance into the water. Released from a special
organ, the hypobranchial gland, it flows out through the slit in the
shell. What's interesting is that the substance doesn't immediately
diffuse into the water. It tends to hold together
like thick smoke in still air. Jerry suspects the secretion is used
to deter predators and may affect the nervous system. But who's nervous
system? These snails almost always show signs of shell repair and the
damage is likely caused by crabs trying to get at the snails. Jerry
"milks" the snails to collect and analyze this substance.
This is the kind of thing that is not only interesting, it could possibly
prove to be a useful substance to medicine.
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