|Conical-shaped shells we found on the beach along Lake Erie at Maumee Bay State Park.|
Thousands of these spiral-shaped conical shells were clumped along the beach at the water's edge at Maumee Bay State Park (near Toledo, OH). They were all in perfect shape and incredibly beautiful. I know nothing about shells, so I took a handful home to learn about them. After a few Google searches, I found a NOAA site from the Great Lakes Environmental Research Laboratory (GLERL), and learned these beautiful little shells had once been homes to aquatic algal grazers in the gastropod family, commonly know as...snails!
|Thousands of the shells were clumped together near the water's edge.|
From the photos and the descriptions on the GLERL page, I'm guessing these shells are Pleurocera acuta (common name, Sharp Hornsnail). According to the information on the webpage, these snails are native to the Great Lakes and Ohio River. They like to burrow in sand and mud, and they like the slower flowing areas of rivers near the bank. I'm going to start looking for them along the Little Miami River. Since it drains into the Ohio, they might be there too.
|The color variations among the Sharp Hornsnail (Pleurocera acuta) shells are beautiful...greens, ambers, blues, browns, pinks, maroons, and whites. It will be interesting to see if the colors fade over time.|
|"Whorls" are the rings spiraling the conical shell. Pleurocera acuta can have up to 14 whorls. |
After checking the shells I brought home, I found most had between 9 and 11 whorls.
|Although they look like black and white stripes, closer inspection shows the dark stripe is really a dark chestnut brown.|
|Sharp Hornsnail shells from Lake Erie (Pleurocera acuta)|
If you want to learn a little about snail shell morphology, click here for the paper, "North American Freshwater Snails," by J. B. Burch, and go to page 25 (in Walkerana, 1986, 2(6) on the Freshwater Mollusk Conservation Society (FMCS) website. You can learn about the whorls, aperture, shell size, and shell shapes, e.g., the shape of our little Sharp Hornsnail is "elongate conic." This booklet is packed with a lot of information.
Freshwater Gastropods of North America is a blog with higher-level scientific info. Click here for a link to "Pleurocera acuta is Pleurocera canaliculata," by Dr. Rob Dillon. Just like in birding, it seems the species names of gastropods can change!
Where did the colors come from?
In the comments section, Mary Ann asked if I new why the same mollusk would make shells in various colors. I didn't, so I did a quick check to find out. Click here for a blog post by Richard Goldberg titled, "The Significance of Snail Shell Color and Pattern" (6-19-2009) on the Art and Science of Nature blog. Goldberg explains that these varied colors ("inter-population variability") can be explained through evolutionary science, mentioning "extreme color polymorphism" in a population is good, because "looking different from your neighbor" prevents predators from developing a "search image" for its prey. Read the article for more details.
As for the colors themselves, they are produced in many ways, including pigments the mollusk acquires from what it eats, pigments the mollusk produces to strengthen shells, hereditary colors to offer camouflage, and much more. Click here for an article by Gary Rosenberg titled, "Why do Shells Have Their Colors?" on the Conchologists of America, Inc. website for details.
I emailed Dr. Rob Dillon, a professor in the Department of Biology at the College of Charleston, to make sure I had identified Pleurocera acuta correctly. He replied that I did (yeah!). But there's more...in 2013 Pleurocera acuta received the trinomen "Pleurocera canaliculata acuta" as a subspecies and "junior synonym" of canaliculata. (Pleurocera acuta was first described by Thomas Say in 1821 as canaliculata and the new name reflects that history.) Thanks, Professor Dillon! See the paragraph above under "Further reading" for a link to Dr. Dillon's blog. Click here if you want to learn what a subspecies is.
This post is part of our "Big Water" trip to Maumee Bay. Click here for more posts in the series.