Editor’s Note – This essay was subsequently published as: Dillon, R.T., Jr. (2023c) Snails by Mail. Pp 45 – 49 in The Freshwater Gastropods of North America Volume 7, Collected in Turn One, and Other Essays. FWGNA Project, Charleston, SC.
Last month we surveyed the elements of the freshwater
gastropod fauna widely available to hobbyists in the Big Box retail outlets
that seem so dominant on the landscape of aquarium supply today [1]. We found two categories of snails reliably offered for sale, strikingly different in their biology but ironically similar
in their provenance – the “mystery snails” (Pomacea bridgesii/diffusa) and the
nerites. But, as my readership has already
doubtless inferred from my essay of 9Oct17 [2], ampullariids and neritids do
not the entire market comprise. What
else might be available online?
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| Assassin Snail - Aquatic Arts |
If one simply enters “freshwater snails” on the subject line
of a google search, the first 50 hits include four major retail suppliers –
Amazon, eBay, aquaticarts.com, and liveaquaria.com. Most of the stock available for purchase from
these sources are (once again) nerites or mystery snails in their various color
varieties. But below I have compiled a brief review of
the remainder, sorted into seven pigeonholes.
The first four taxa or groups of taxa appear to be widely available for
purchase online, the next two categories seem to be occasionally available, and
the last category is what I would call a “wastebasket.”
Ramshorns – These easy-to-culture snails seem to have
remained a perennial favorite of aquarium hobbyists for many years, at least since
I was a kid. All the stocks with which
I had any personal experience growing up were North American Helisoma trivolvis, but today it is my impression that most "ramshorns" are Floridian Helisoma scalaris duryi [3]. Ng
and colleagues [4] identified Singapore ramshorns as Oriental Indoplanorbis
exustus, on the other hand, and I've even seen European Planorbarius corneus implicated in what seems to be a global planorbid conspiracy. What the heck are these snails? Most of the offerings for sale online today are “red ramshorns,” which are
actually albinos, their absence of body pigmentation allowing that red
hemoglobin so characteristic of planorbids to show through. Stocks with wild pigmentation are marketed as
either “brown” or “black.” There is also
a “leopard” variant for sale that has patchy pigmentation on its mantle, and a
“blue” that (I think) demonstrates some sort of mutation in shell pigmentation. I wish I knew more about that, too.
Assassin Snails – Approximately thirty nominal species of the
nassariid genus Clea (or Anentome) burrow in the soft bottoms of broad, coastal
rivers from southern China and Southeast Asia into The Philippines. What fascinating creatures! The group is one of only two neogastropod
genera to have successfully invaded fresh waters [5]. As their name implies, assassin snails are
predatory – hunting other freshwater snails and sucking them out of their
shells. The little tigers widely marketed
to the aquarium hobby today are universally identified as Clea helena, but the
excellent recent study by Ellen Strong and colleagues [6] suggests that
commercial stocks may represent as many as four species, none of which seems to
match topotypic Anentome helena from Java.
Rabbit Snails – Several species of the pachychilid genus
Tylomelania are not uncommonly offered for purchase online, variously marketed
as “giant” or “orange” or “golden” rabbit snails. It may be recalled from my October essay that
Ng and colleagues [4] identified four Tylomelania species in the Singapore aquarium trade, all of which are apparently endemic to Lake Pozo on the
Indonesian Island of Sulawesi. Some
conservation concern has been expressed, but see the follow-up essay I
published on this subject in November [7].
Japanese Trapdoor Snails – Yes, our old familiar Bellamya
japonica (or maybe B. chinensis?) often seems to be marketed to the indoor aquarium hobby, generally labelled as "Viviparus malleattus.” The biology of these large oriental
viviparids will be well known to my FWGNA readership, but see my species pages
[japonica] and [chinensis] for a refresher.
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| Rabbit Snail - Aquatic Arts |
Pagoda Snails – Several nominal species of the pachychilid
genus Brotia bearing heavy, strikingly spiny or tuberculate shells are
harvested from the rivers of Thailand and occasionally available from online
retailers as “Pagoda snails.” We touched on these back in October as well.
Chopsticks, Spikes, or Long nosed Snails – Occasionally the discriminating freshwater gastropod connoisseur will find thiarids of the genus Stenomelania offered for sale online. Again, Ng and colleagues [4] identified four
Stenomelania species marketed in the Singapore pet trade, although raising no
conservation concerns. The Discover Life
website lists 36 nominal species in the genus, ranging throughout Southeast
Asia, Australia, and Oceania. The most
common specific nomina mentioned in the pet trade are Stenomelania torulosa and
S. plicaria, both distributed widely from India through Indonesia to China.
The Wastebasket – Although (almost) universally reviled,
stocks of the “Malaysian Trumpet Snail” (Melanoides tuberculata) are available
for purchase on Amazon and eBay. This
invasive thiarid, apparently native to low latitudes throughout the Old World
(in various clones), has been widely introduced into the New. See my FWGNA species page [tuberculata] for
more. And (if you can believe it)
hobbyists with a thirst for the small, brown, and mundane can also purchase
Physa acuta stocks from Amazon. I get
the impression that both the Physa and the Melanoides are primarily marketed as
prey for Assassin snails. The Physa
listing on Amazon advertises, “great natural food for your puffer.”
What I did not find for sale online last week, thank heaven, was any
ampullariid stock other than Pomacea bridgesii/diffusa. I remember in years
past being able to purchase, at least occasionally through mail order or
mom-and-pop aquarium stores, Pomacea insularum/maculata (“Golden Apple
Snails”), Pomacea paludosa (“Florida Apple Snails”) and Marisa cornuarietis
(“Giant Ramshorns.”) But I was unable to
find, at least upon superficial search, any listing for any such invasive ampullariids through the major online retail outlets today.
So to conclude. Should we be concerned that any of the freshwater gastropod groups listed above might escape to become pests here in North America, other than the ones already
introduced and spreading? We have reviewed
the criteria for invasiveness on quite a few occasions in the past [7],
ultimately settling on two ecological qualities which I have called “weedy” and
“different.” So the ramshorns,
trapdoors, and wastebaskets are already here.
And the rabbits, pagodas, and chopsticks are not all that ecologically
different from North American pleurocerids, in many cases, nor do their life
histories seem especially weedy. That leaves
the Assassin snails.
Could an introduction of Clea succeed here in North America? Some concern has already been expressed [8]. All the range maps I have seen for the genus
seem to suggest that their natural distribution is entirely tropical –
apparently ranging from the equator to around 20 degrees N latitude. So our own Key West floats in the Caribbean
at latitude 24.5 degrees N, perhaps still a bit too temperate to raise concerns
about the threat of gastropod assassination here in the USA. But you all down in Mexico and Central
America might best be on the lookout.
Notes
[3] Subsequent to the publication of this essay I posted a lengthy series on Helisoma scalaris duryi, starting in October of 2020 and going onward for at least five or six months. I do suggest that you skip ahead here and read forward into 2021 if you are genuinely interested in "ramshorns":
- The flat-topped Helisoma of The Everglades [5Oct20]
[4] Ng Ting Hui, Tan SK, Wong WH, Meier R, Chan S-Y, Tan HH,
Yeo DCJ (2016) Molluscs for Sale: Assessment of Freshwater Gastropods and
Bivalves in the Ornamental Pet Trade. PLoS ONE 11(8): e0161130. https://doi.org/10.1371/journal.pone.0161130
[5] The only other neogastropod group to invade fresh waters
is the marginellid genus Rivomarginella.
[6] Strong EE, Galindo LA, Kantor YI. (2017) Quid est Clea
helena? Evidence for a previously unrecognized radiation of assassin snails
(Gastropoda: Buccinoidea: Nassariidae) PeerJ 5:e3638 https://doi.org/10.7717/peerj.3638
[8] For the biology of freshwater gastropod invasions, see:
- Invaders Great and Small [19Sept08]
- Community Consequences of Bellamya Invasion [18Dec09]
- The Most Improbable Invasion [11Oct12]
- The Many Invasions of Hilton Head [16Dec15]
[9] Mienis HK. 2011. Will the uncontrolled sale of the
snail-eating gastropod Anentome helena in aquarium shops in Israel result in
another disaster for Israel’s native freshwater mollusc fauna? Ellipsaria
13(3):10-11. Bogan AE, Hanneman EH. 2013. A carnivorous aquatic gastropod
in the pet trade in North America: the next threat to freshwater gastropods.
Ellipsaria 15(2):18-19
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