Adanson's Slitsnail and the Science Behind the Expedition

Off Chub Cay, Bahamas, Day 3, 1999Dr. Harasewych recounting the dive. Specimens are in buckets

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 Adanson's slitsnail under a rock ledgelarger 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 exceptTypical scene of rock, corals and sponges 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.

Pat and Steve working in the dry lab after a day of diving

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. Secretions collected from MidasIn 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 Adanson's secretionstogether 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.

Smithsonian, National Museum of Natural History