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New Library Article - Thiara amarula - Spiny Marsh Snail


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Thiara amarula

Spiny Marsh Snail

 

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The Spiny Marsh Snail is an Australian native that is rarely found in the trade. This is a shame as it has an interesting shell shape and is well suited to aquarium life, providing a few simple conditions are met.

The Spiny Marsh Snail was first described by Linneaus in 1758 as Helix amarula, with a subsequent remaining of the genus to Melania in 1822, and finally to Thiara in around 1943. It is found from the east coast of Africa, through Madagascar, north to the Philippines, through the Solomon and other Pacific Islands, and along the north-eastern coast of Australia (See Schutt & Glaubrecht, 1999 for a global distribution map). Given this widespread distribution, it is surprising that its distribution in Australia is limited. It is found from the Bloomfield River (south of Cooktown) to approximately 100km south of Cairns. Thus it is limited to around 6 major tributaries.

The Spiny Marsh Snail is found in the lower freshwater sections of rivers, generally just above the tidal range. It is probably tolerant to low levels of salt as it would be exposed to brackish conditions in drought years, and therefore may be suitable for brackish aquaria. This requires further investigation.

In its natural habitat, the Spiny Marsh Snail is found amongst rocks and pebbles, but also sandy areas, which is where I found them in the Johnstone River. In aquaria, they regularly bury themselves, especially when exposed to bright light. However in low light, or if the tank is densely planted or shaded, they are happy to move on top of the substrate and even climb the walls. This makes them useful for removing dead spots in substrates, but may mean they could dislodge plants in heavily planted aquaria, but I have not kept them under these conditions – something to watch for.

I have noticed they are particularly active at night and may graze algae from the glass during this time. I've seen no indication that it eats plants, and indeed plants are generally absent from its natural habitat, other than Vallisneria or Aponogetons. They happily eat prepared foods (shrimp/fish food) as well as some greens (cucumber/zucchini). However, they seem to spend most of their time grazing.

The Spiny Marsh Snail grows to a maximum size of approximately 50mm, perhaps slightly larger. From what I've seen, they are fairly slow growing and long lived. This makes them excellent candidates for aquaria, because unlike other pest snails, it makes it easier to control their numbers. Indeed breeding in aquaria is unlikely because it is thought the Spiny Marsh Snail releases planktonic larvae that move into the brackish/salty areas of rivers before migrating back up the river to settle. However, the true breeding habits of this snail are still unknown and present a challenge for aquarists. Nevertheless, these characteristics make it unlikely that the Spiny Marsh Snail would ever be a pest in aquaria.

One condition that seems to be an absolute must for this snail is that pH needs to be 6.5 or above. In acidic conditions (pH < 6.0), the shell dissolves and the snails refuse to come out of their shells. If your snails are not active, check your pH. That said, this doesn't mean that they require lots of dissolved minerals (e.g. calcium carbonate). The TDS of the Johnson River where I found these was only 28 ppm at the time, so Spiny Marsh Snails may be the perfect tankmates for Neocaridina shrimp (cherries) and Australian native shrimp, but less so for Caridina (crystals, bees, etc.).

So if you are after a snail that is good looking, hardy, a good algae eater, turns over the substrate, easy to feed, won't bloom into a pest population, is native and presents a breeding challenge, I highly encourage you to track down some Spiny Marsh Snails. Why not try a biotope tank with Vallisneria or Aponogetons and Caridina gracilirostris?

Some additional material worth reading.

Field trip to Johnson River, Queensland Australia with habitat description and pictures.

http://www.naturkund...brecht_1999.pdf

Atlas of Living Australia – shows the collection points of Thiara amarula in Australia.

http://bie.ala.org.a...e-f394430ec676#


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