Malayan Trumpet Snails (Melanoides)

Malayan Trumpet Snails (MTS). Melanoides tuberculata. Red-rim Melania. The exception to my uffish snail ban is "Red-Rimmed Melania," Melanoides tuberculata, the "Malayan Trumpet Snail" of aquariums, and the less-common M. turricola, "Fawn Melania". You'll recognize them in a flash because they're small, up to 3/4 of an inch (3.5cm) — M. turricola being somewhat larger — and because their cornucopia shells taper like ice cream cones. The little bumps, or tubercles, that give M. tuberculata its name are seen better under a magnifier.  Some researchers feel that Melanoides is masculine: hence, Melanoides tuberculatus. Sex is optional for Melania: some populations contain a minority of males, but many natural populations of M. tuberculata are exclusively female, reproducing parthenogenetically and protecting the eggs and developing snails internally in brood pouches. Minute but fully formed young are released at the water surface.
 
The shape of Melania shells is a useful adaptation to life in fast-moving waters: the tapering end naturally swings round to point downstream, and the reduced turbulence, as water passes over the hydrodynamic shape, helps the little gastropods cling to their place or creep upstream into your filter. These snails are welcome in any aquarium. One exception might be a tank in which fish are spawning, if all snails will eat fish eggs (see below). Of course so will just about all fish!
 
Melanoides snails burrow into the substrate like earthworms, leaving their enriching feces behind to fertilize plants better than any tablet you might try to poke down there. They don't do quite as much subterranean plowing around as is commonly imagined, but at night they come out to feed on detritus and algae. They never touch a healthy growing leaf. Melania can probe into mildly hypoxic areas in the gravel, and by doing that they reopen it to the slow diffusion of oxygen. These thiarid snails, like all greens-eating animals, depend on intestinal flora to break down cellulose.
 
A snail shell, like all mollusk shells, is built up in three layers. The inner two are structural; they are formed of calcareous crystals. The patterned organic outermost layer is protective; it helps keep the calcareous inner layers from being dissolved in acidic environments. Often snail shells become pitted anyway, in very soft acidic waters like mine. Melania are more resistant than most snails to this shell degradation; usually the pitting is visible only at the smallest, thinnest, oldest part of the shell, the tip of its cornucopia. The adult snails' proportionally thick shells also offer them some defense from your Botia and other snail-eaters.
 
Being livebearers as well as optional  parthogenetic females that don't need to be fertilized, Melanoides species can reproduce with a rapidity that puts them on the pest list for those aquarists who are intensely concerned with issues of control. Depending on temperature, they go to the water surface at night to release cohorts of minute, floating young,  fully formed with five or six shell whorls, which  have developed together as embryos in brood pouches. Some fishkeepers react like Mickey in The Sorcerer's Apprentice: not I. I don't want the critters to go extinct, I just want them in balanced populations. But their numbers are easily kept in line, for they are on the Botia menu, as long as the snails' shells are still small enough to crack (newborn snails are 1.5 to 2 mm long).
 
 
 
Feral Melania! Melanoides tuberculata, common in tropical Africa and Asia, have been introduced in all the tropical and sub-tropical regions of the world since the Second World War, largely through the trade in aquarium plants. In some places, like the marshy forest zones of the Caribbean islands of Saint Lucia and Guadeloupe, it was purposefully introduced as a competitor of the local snail that is the intermediate host of the dangerous human parasite Schistosoma. M. tuberculata was originally introduced to American aquarists by a San Francisco tropical fish dealer in 1937. Soon a dealer in Tampa Bay FL bought some from California and sold them as "Philippine horn-of-plenty snails." It's a nice name, for their tapering shells do remind you of a cornucopia. Since then, feral Melania have established themselves irrevocably in Florida, where they have even proved tolerant of high salinity in brackish mangrove swamps on the Gulf Coast. Other Melania populations are prospering in some canals in New Orleans, and in Texas, where they were first noticed in 1964, they have spread from a population found in 1990 in headwaters of the San Antonio River to many locations in central and west Texas. Feral M. tuberculata are spreading southwards through Mexico, and they have also established a toehold in Minas Gerais, Brazil. Eight days at 50^o (11^oC) will eradicate them, experiments found, which limits their eventual spread, though they have been reported (2002) in a warmwater thermal spring in ecologically fragile New Zealand.  All these escaped populations were originally seeded by thoughtless aquarists. It's only too easy to flush a snail down the toilet when you're doing a water change.
 
Aside from outcompeting native snails, a serious problem is that Melania may carry a fluke (digenetic trematode) that completes part of its life cycle in the snails' digestive glands, then moves on to infest the gills of native fishes. Here in the States, several endangered darters, minnows and pupfish are being affected. The fluke's adult phase is passed in fish-eating birds, especially Night Herons. The trematode can't complete its life cycle in the aquarium, but it may be an issue in planted outdoor ponds.
 
See Red-rimmed Melania at Wikipedia. A page of Melanoides details as seen from the perspective of the US Army Corps of Engineers gives you their vital statistics. There's a brief discussion of these feral snails and associated parasites at theUtah Division of Wildlife Resources, as the spread of Melanoides to warm-water springs is a threat there.
 
Melanoides turricula. ("Fawn Melania"). These get to be a little larger, as I said, almost an inch long. The strain in my tanks tends to have light olive-brown shells. I got my first Fawn Melania several years ago, as a rarity, from a LFS, for free. A rarity indeed! they thought I was a little barmy to be asking for them. A snail researcher (Thompson, in 1984) was unsure whether this was a genuine species, or just a Philippine variant of the widespread M. tuberculata, but, interestingly,  the two species have separated themselves out in their adopted Florida ranges, M. tuberculata in quieter, enriched turbid waters and M. turricola in cleaner, clearer springs. In my tanks the two types have remained quite recognizably distinct.
 
Melanoides and related genera in the family Thiaridae are described and very briefly discussed and illustrated at the University of Florida Museum of Natural History site (Scroll down to the Thiaridae (section 16, figs. 40-44.) This is a passionately devoted scientific site for snail geeks.
 
About Melanoides in a hang-on-tank filter. Detritus always gathers on the intake stem of your hang-on-tank filter, like autumn leaves on a storm-drain grate. Melania are attracted to detritus, and some of them are so minute they can get sucked past the pump impellor into the h.o.t. filter. There they grow fat and happy grazing on the upstream face of your filter sleeve. You may notice them first simply because that slippery brown "gunk" isn't collecting there the way it used to, and you no longer have to rinse your filter once a week. Gunk is now being transformed to Snail! How completely desirable, in my opinion! such a large mass of Gunk translates to so very little mass of Snail. I'm putting entropy to work for me! Only some of the potential energy that was represented by nitrogen-rich Gunk is actually converted to Snail, where it helps build soft organs and shell, or is used for tissue repair or metabolism. The rest is dissipated in metabolic end products like molecules of water and carbon dioxide and in ripples of water displacement and minute amounts of heat. That process is called entropy. And, since all natural systems are leaky, there are some further metabolic byproducts to be broken down by bacteria. Ammonia is the first one to come to mind. Bacteria are constantly scavenging the ammonia that snails give off, perhaps converting it right there in the filter, though some may escape to fertilize the plants and algae. But the filter snails are even cropping the nitrifying bacteria that are part of the filter Gunk. Which is good for the bacterial population... Snails in the filter? "They're a Good Thing." So, now, when I do rinse the filter frame, a shake and a tap or two induce some of the snails to let go. They roll off the filter and get "exported" from the entire aquarium ecosystem, along with the wastewater. That percentage of Gunk-derived nutrients and minerals that are represented by Snail mass, finally gets eliminated from my closed ecological system. Snails in the h.o.t. filter are a wholesome and useful part of the energy path, and you see now how they also form part of the biofiltration system, which is otherwise largely bacterial.
 
There's a slight downside to a snail colony in the filter: once in a long while a small snail may struggle against the current and manage to get caught in the impellor, producing a noisy clatter, and I'll have to flush it out. It's a small price to pay. Is it foolish of me even to consider that the snail shells I'm exporting from the system do represent a certain amount of calcium, and that there's a minute water-softening consequence here? When I leave a larger, decorative snail shell to lie dissolving slowly in my soft acidic water, I notice that Melania are drawn to it like deer to a salt lick. Are they taking up the calcium they need?
 
A caution: Melanoides tuberculata can serve as the first intermediate host for the human lung fluke and for the human liver fluke. The second intermediate host is not a human being, though, but must be a crustacean that eats the snail. There could be serious consequences in these exotic snails, now ineradicably feral in Florida waters, at some time in the future. For now it's not a worrying thought. Unless you indulge in raw crayfish sashimi from Florida, that is. I doubt a single case of parasitic flukes will be traced to feral populations of these snails. For one thing human fecal matter infested with liver fluke eggs has to find its way back to the water, or the cycle remains incomplete. But you should know about this remote future possibility.