02 December 2007

Mysterious snails of the Potomac


Last weekend while visiting DC, we walked along the Potomac River at one point. In the mud left behind the previous tide, there were these large snail shells.


I am not very good at identifying freshwater snails, but in this case I am putting my money on the Japanese mystery snail, Cipangopaludina (Bellamya) japonica, a native of Japan, Taiwan and Korea.


I have 3 more even larger shells. But they had a thick coat of algae growing on them and were starting to get smelly. So I put them out in the backyard to get them cleaned by the ants and whomever else may be interested in eating such stuff.

The juvenile shells, also from the same location, have 3 keels along their body whorls.


According to this source, this species has been in North America since at least the mid-1900s. They have since spread widely and appear to be "naturalized" in North America. Once an alien species comes to that point, there really is no way of getting rid of it.

There is also the Chinese mystery snail, Cipangopaludina (Bellamya) chinensis, another introduction from Asia. I don't know why these species are called "mystery snails".


Charlie Sturm said...


We have this taxon in western Pennsylvania. I have collected them at Yellow Creek State Park, Indiana County.


Laura Saltzman said...

Oh man! I'm a ecology college student who spent the summer researching the Chinese mystery snail in New York. These are definitely japonica, you can tell by the elongated spire in of the shell in comparison to chinensis. There's some debate as to whether they are two distinct species, or just a morph. Clear differences can be seen in the number of whorls and location of periostracal hairs in the embryos, though. Those are certainly some giant ones, I think the largest I found over the summer was 64 mm in a pond in New Paltz.

All research points to them being relatively innocuous, but the sheer size of the population in the average infected body of water does give pause.

Laura Saltzman

pascal said...

Interesting carinate morph. It appears to be a common feature in some groups of gastropods.

My master's project involved identifying phenotypic variation in Pleurocerids from the Eocene Green River Formation in Wyoming.

It's an adaptation I'd like to investigate further...

fabrizio said...

Excuse me, they retain the carinate morphs when adult too, or does that coalesces as long as they grow on?


The lowest carina (keel) is still present along the body whorl of the adult shell, but it is less prominent. If you look at the 2nd picture from the bottom, you will notice that the smaller snail on the left has a somewhat sharp corner along the left side of its body whorl. That's the carina.