|MadSci Network: Zoology|
Well I'm no snail expert but, thanks to your question, I have had make a quick step toward being one. For your information, there is an extensive range of information the numerous varieties of Mollusca Gastropoda Pulmonata (or freshwater snails). If you're really keen check out the links on http:// www.fw.umn.edu/Personnel/staff/Hove/Mussel.web.sites Most are university links here so the information can be trusted. The site that most helped me in my rushed research for you was The trail of the snail which is at http://members.t ripod.com/arnobrosi/aquasnail.html However, if you just want an answer to the questions you asked then... In short, yes you are finding the reminants of a meal. Snails are connected to their shells by a muscle on their body, the same connection that allows them to quickly retract into hiding. Unlike hermit crabs, who outgrow their shell and move into another, the snail doesn't willingly leave its protection. Snails are the minature cows of your lake, spending their time grazing on algae and plants. Being slow and with minimal defenses they have an extensive list of predators from parasites to fish, from other molluscs to water birds. Not all of which would leave the sign that the snail was pulled out of its shell. Other than the protection of their shell their other defenses relate to hiding away where they can't be found and/or feeding when their predators are not. The fact that you hardly ever find one living is testimony to the fact that they do this quite effectevely. If you are trying to find some living ones I suggest you check out a handbook on doing so. Provided by Freshwater Mollusk Conservation Society Committee on the Status & Distribution of Gastropods, this link would be very helpful to you. It will also help you identify ones you do find (shell or whole). http://www.cofc.edu/% 7Edillonr/Dillon_FW_Gast_Chptr.pdf Please remember that you cannot take animal or plant matter from some areas including national parks etc. In fact I suggest you don't take anything from anywhere. After all what you take may deprive something from a meal or a home. Even empty and deteriorating shells return nutrients back to the lake. Also note that some cone animals are extremely poisonous in some parts of the world (eg. where I'm from - Australia). All the best. Peter
Try the links in the MadSci Library for more information on Zoology.