For a change of pace, a fresh water gastropod, which means I did not find these in the Back 40. The species is a Brooklyn resident, however: I took this photo at the Valley Water in Green-Wood. I think the snail is Viviparus malleatus, the Chinese mystery snail, a.k.a. the Japanese trapdoor snail. (Like many of us, these come from somewhere else.) What you see above is, I think, only half the size of the shell of the living creature. I was lucky to find this much. Mostly, it’s all shards. The pond’s stone edge is littered with broken shells. Something eats these critters like no tomorrow. The shell is particularly thin, so it seems to be easy to crack, spear, smash.
Snail Tales, part III
4 responses to “Snail Tales, part III”
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In relation to your “Green-Wood” snails, it may be instructive to add that, whatever they are and wherever they came from, they are also currently present at Mill Pond in Wantagh, NY, an attractive small park and nature reserve in south-central Nassau County, at the NW corner of the intersection of Wantagh State Parkway and Merrick Road.
There, they are found along the shoreline in wooded areas but in smaller numbers than you indicate for Green-Wood, and not as shards but as partly broken shells. They are typically found on open, sometimes mossy ground among the nearshore trees. I share your impression that something (raccoon? opossum? Canadian geese? ducks?) has been feeding on them, and presumably fishing for them, since they seem to be freshwater snails.* The difference in breakage suggests the possibility that different predators are responsible in Wantagh and Green-Wood.
[*The shells are relatively light and fragile for a land snail of such a size, the size itself is rather large for a temperate region land snail, and another website indicates that no such high-spired snail has been recognized to date among the land snail fauna of the northeastern U.S.]
I looked in the shallow water of the pond, but I could not distinguish any snails among the thick cover of greenish-brown decaying leaves, over a sandy bottom. The fallen leaves, however, would appear to provide excellent food and cover for these snails.
I have not seen such snails on Long Island before. Although I have not been resident on LI for many years, my experience includes intermittent hiking and nature observation on LI as a visitor over several decades. I ought to have noticed them previously had they been present, which makes me suspect the relatively recent introduction of a foreign invasive species.
I would be interested to know if and when there has been a definitive determination of the identity of this snail (your own tentative identification sounds both confident and likely), as well as an educated assessment of the possibilities for how and when it came to be in the greater New York area.
I am able to convey this information thanks to a flight delay occasioned by the eruption of Mt. Eyjafjallajokull, which allowed me to visit Mill Pond this morning, 20 April 2010. So there really is a silver lining in everything. I was disappointed, however, at the paucity of information available online about the freshwater and land snails Long Island, NY and the northeastern U.S. generally.
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I’ve not “fished” around in the pond to find a live one of these, so my ID remains tentative. I visited this past weekend and it is thickening up with water lillies, getting murkier. Plenty of shattered shells on the stone edge of the water though suggests there are plenty in there.
If I’m right about the ID, then these snails have spread via aquarium dumps, people getting rid of their no longer wanted aquariums; also, they have sometimes been introduced to filter ponds because they are algae eaters.
I hear the air’s clearing and flights are heading over the big pond. Have fun.
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r u sure these r green-wood snails
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Yes.
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