by Brady Raymond
Well, folks, it’s perfect mushrooming weather, though unfortunately, it is January. Now, that’s not to say there are no mushrooms to be found, but, it’s unlikely to yield much for the hungry mushroomer. I myself haven’t been out beyond walking my dog and the like. I have spotted some mushrooms but they are either desiccating or desiccated take your pick. So, why not take an interesting deviation from the norm and talk about some other interesting lifeforms Mollusks, more specifically Gastropods of the land variety.
Why would Gastropods be of any interest to a mushroom hunter? Most mushroomers I know posses at least in small amounts some degree of nerdism. I would be willing to bet that if you’re still reading this article you may possess high levels of nerdism. Undoubtedly you’ve encountered these creatures both in your yard or garden as well as our native habitats. Heck, you probably have even picked a few off of some mushrooms at one time or another. Plus, anyone interested in identifying mushrooms will feel at home trying to put names on Gastropods. There are dichotomous keys similar to what you’d find in an ID book for mushrooms, breaking down different morphological features such as shell size, pneumostome placement on the mantle, flesh textures and mucus consistency.
Mollusk is a Phylum of life residing in the Animal Kingdom. It is a diverse Phylum only exceeded in the Animal Kingdom by Arthropods. There are some 110,000 described species that make up the four main classes consisting of the Chitons, Bivalves, Cephalopods and the Gastropods.
Chitons-are the most primitive mollusks grazing on marine algae in coastal waters.
Bivalves-have hinged shells and filter the water for nutrients. Mussels, Clams, and Oysters are examples of this group and they are an important species to people as a food source.
Cephalopods-are the most intelligent of the invertebrates. They have sophisticated nervous systems and are quite mobile. Many species skin contain chromatophores which allow them the ability to change color depending on mood or for concealment purposes. Think Squid, Cuttlefish, and Octopus. One can only imagine what they may evolve to be in 100 million years!
Gastropods–are the largest class of Mollusks. Most are marine in nature where they evolved but others have adapted to freshwater and land. Most Gastropod diets are vegetative but a few species are predatory. Many Gastropods have shells yet others have lost their shells in the evolutionary process. We will focus on land snails and slugs from here on.
Malacologists estimate the number of land Gastropods to approach 35,000 species worldwide. That is more than all the vertebrates combined excluding fishes. Slugs and snails are quite well adapted to their varied environments, which is everything from temperate to tropical forests, alpine tundra, grasslands, and deserts.
Being such a diverse group one would expect these creatures diets to be just as varied, and it is. Land snails and slugs diet may consist of plants, fungi both living and dead as well as other organic detritus. Some feed on carrion and a few are predators.
The word Gastropod is derived from the Latin and means “stomach foot.” They produce mucus for a number of reasons one of which is to aid in locomotion. Gastropods propel themselves forward by means of muscular contractions in a wave-like pattern gliding across a trail of their own mucus.
Gastropod reproduction is not for the faint of heart. For the most part, Gastropods are hermaphrodites, each containing sperm, and egg. Most scenarios require two individuals to mate but self-fertilization is not unheard of. In many cases, identification to species may require dissection almost always focusing on the genitals. It can start to get convoluted as there is much to learn on the topic of Gastropod reproduction, some of which I’m still trying to wrap my head around. But, for the curious, here is a link to a scene from Life in the Undergrowth narrated by David Attenborough and produced by the BBC. And yet another link to Everything You Never Wanted to Know About Snail Sex an episode of Deep Look by PBS Digital Studios.
Much like mushrooms, making detailed observations of your specimen is very important when trying to identify specific Gastropod species. Anyone familiar with the dichotomous keys of mushroom ID guides will feel at home using the similar keys provided in Land Snails and Slugs of the Pacific Northwest by Thomas E. Burke, and Land Snails of British Columbia by Robert G. Forsyth. I highly recommend both of these editions to your home library if you have any interest in snails and slugs. The two volumes together are really great. Each book has enough different information than the other to warrant owning both complementing each other well.
Note on the specimen pictured above where the pneumostome is, posterior on the mantle. This was one key to identifying this slug. In some other gastropods, the pneumostome or “breathing hole” is more anterior on the mantle as observed in the image of Arion rufus above this image. Overall this slug was probably around 4 or 5 centimeters fully extended, its mantle and body were more or less the same color and its mantle had a fingerprint-like pattern which is tough to see in this image. Along with this lighter specimen under a board in my yard, there were darker colored specimens too. After doing my best at keying it out and cross-referencing, I came to the conclusion that this was Deroceras reticulatum, an introduced species from Europe.
Snails are a little different than slugs in that they have shells. For the observant, shells can be found relatively easily, at least for the more common species. Even when it’s to dry for snails to be out the shells of the dead lay about around one’s yard or local forests, etc… If you do find a shell, do your best to describe it. Measure both the width and height, count the whorls and note the texture of the shell. Look closely at the apertural lip (the edge around the opening of the shell), note whether it is thin, flared, recurved or thickened. Look inside the aperture, note any apertural denticles or more simply said shell protrusions, which are unique to certain species but not found in all.
Look at the color of the shell, note how translucent or opaque the shell is. Sometimes it is both as in the shells pictured below. Both shells are that of Oxychilus draparnaudi. The shell on the left depicts the apex side of the shell and on the right the umbilical side. In this species the apex side of the shells tend to be quite translucent whereas the umbilical side is more opaque, it’s tough to see in the image but is clearly visible in person.
I found these to shells under some wood out by my garden along with some living specimens pictured at the beginning of this article. I had the advantage of observing both the living organism and finding some unoccupied shells. The first thing I noted was how blue these little snails were, they come across gray in the photo but they were quite blue in person. I also noted one specimen eating the carcass of a sowbug.
After taking measurements of the shells I keyed them out the best I could and arrived at Oxychilus cellarius but this description clearly stated that when disturbed they would produce a strong smell of garlic. I had put a few of the living ones I found in a jar along with the sowbug carcass to observe and there were now three snails feeding on that poor old sowbug. I opened the lid and disturbed them a bit with my finger. I couldn’t smell anything. On top of that, they were described as having a gray body, not a blue one. I was a little discouraged until I turned the page and read the description for Oxychilus draparnaudi.
O. draparnaudi was described as being slightly larger than O. cellarius which was more in line with the sized shells I had. They were described as not having any scent and were unmistakenly blue bodied. I was pretty sure I had made a correct identification. I read a little further and it talked about eating other dead invertebrates (sowbugs are invertebrates of the crustacean kind). I was getting excited until I read that it is a common introduced species usually found around human dwellings. I should have figured as much as there were nearly thirty under the board.
Unfortunately, all the snails and slugs in this article are introduced species. As far as I can tell they are from Europe. I have a few more shells to identify and maybe some of those will turn out to be native. The problem is the shells I have remaining to be ID’d are only a millimeter or two in height.
So, as you can see Gastropods and Fungi are kind of similar. They both like wet conditions, they are highly variable both within the larger overall group and also within species, they associate with different habitats and are going through some name changes as well. What’s not to love about these guys/gals, (guyals?). Hopefully, if you made it this far in the article you learned something new. And maybe you’ll have a better appreciation of these interesting creatures. I look forward on occasion to deviate from the norm and share some interesting facts and info on other things PNW. And trust me, there is more to be said on the topic of gastropods, and I intend to do that in time. Oh, and that garlic scented snail Oxychilus cellarius, I ended up finding one and it does smell like garlic. Keep that in mind next time you flip over a log and get a whiff of garlic, look around and you’ll probably find one too.
Land Snails of British Columbia by Robert G. Forsyth
Land Snails and Slugs of the Pacific Northwest by Thomas E. Burke
Biology, Eighth Edition, McGraw Hill Publishing
Natural History, The Ultimate Visual Guide To Everything On Earth, DK Publishing