Dr. Rob Dillon, Coordinator





Wednesday, January 24, 2018

Snails by Mail


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?

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 have any personal experience are North American Helisoma trivolvis, but Ng and colleagues [3] identified Singapore ramshorns as Oriental Indoplanorbis exustus.  I wish I knew more about the relationship between these two taxa.  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 [4].  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 [5] 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 [3] 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 [6].

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.
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 [3] 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

[1] Pet Shop Malacology [21Dec17]

[2] What’s Out There?  [9Oct17]

[3] 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

[4] The only other neogastropod group to invade fresh waters is the marginellid genus Rivomarginella.

[5] 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

[6] Loved to Death?  [6Nov17]

[7] 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
[8] 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

2 comments:

  1. I've had several "blue" H. trivolvis pop up in a culture I have going. They do appear to have normally pigmented bodies with unpigmented shells. There is a similar color variant in Pomacea diffusa (also called blue). I may have to try a few breeding experiments to see what's going on.

    -Matt Hill

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    Replies
    1. Interesting! Yes, breeding experiments on the Helisoma "blue" morph would be a most welcome contribution. Keep us posted on the results!

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