Development

Although, there are no known studies done specifically on development for Stenotrema barbatum, development may be parallel to that of Stenotrema leai. "The Eggs and Egg-Laying Habits of Some Midwestern Land Snails," a study done by Carl W. Gugler, includes a description of the eggs and egg-laying habits of Stenotrema leai. 

In early May, the adults of Stenotrema leai made flask shaped burrows about 1 cm to 2 cm deep, in which they deposited 5 to 10 eggs. The eggs were ovoid in shape, and 1.6 mm by 1.9 mm in size.  They had a whitish, flexible shell.  The shell was made of an outer, gelatinous layer that was about 0.3 mm thick.  Underneath the outer layer was a thinner gelatinous layer. Underneath this inner gelatinous layer, was a 0.1 mm thick layer of irregular, calcareous granules (Gugler, 1903). 

Inside these eggs is were development occurs. Land snails go through a trochophore larva stage and a veliger larva stage inside the egg.  During the veliger larva stage, torsion occurs, which is a 180 degree twisting of the visceral mass, that brings the anus to the same same side of the snail as the mouth (Hickman etal., 2009).

The advantage of torsion is after twisting occurs, the snail only has one opening in it's shell. This aids as better protection for the snail, since predators can only get to the snail from one side of its shell.  When the snail feels threatened, it can withdraw its body into the shell, and cover the single opening with an operuclum (Hickman etal., 2009).  However, this adaptation also introduces a fouling problem since wastes are being expelled in the same area that the mouth is taking in nutrients (Hickman etal., 2009).

After hatching from the eggs, the land snails engage in direct development in which juvenile larva hatch from the eggs and grow into adult snails.  The hatchlings are basically mini adults, so no intermediate larval stages are necessary and do not occur. 

 

 

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