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Author Topic: Fresh Water Snails & Control Management  (Read 2346 times)
EndearDiscus
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« on: June 01, 2010, 04:18:58 PM »

Fresh Water Snails
Snails and mussels are the only molluscs that not only live in the sea, but also in the fresh waters ? rivers and creeks, ponds and lakes - on the continents. While life conditions are quite constant in the vast reaches of the sea (except from the littoral zones), life in fresh water displays constant changes of water supply, temperature and currents, as a result habitats being a mosaic from small living spaces and obliging their inhabitant to adapt very closely to ecological conditions.

In the course of evolution groups related to each other may be isolated by ecological adaptation. The isolation may even go so far, that mating is not possible any more ? a new species has evolved. It is because of this, that fresh water molluscs, mussels and snails, are much richer in species than are their marine relatives.

In contrary to the other, exclusively marine, molluscs, the number of species in snails and mussels is much larger: Of the 55,400 mollusc species known to science, about 53,000 are gastropods or bivalves, of these about 10,000 bivalves and 43,000 gastropods - over three quarters of all mollusc species.

Common River Nerite

The common river nerite, (Theodoxus fluviatilis L. 1758) is a good example to see how the transition into fresh water could have looked like in earth history. There is one subspecies of river nerite, Theodoxus fluviatilis littoralis, that lives in Pomerania, in brackish water, where fresh water and sea water mix in a river mouth. This snail's adaptation to salinity is very sophisticated. This is very energy intensive, which is why this snail species has got a very thin shell, compared to its relatives in the sea, in fresh water and on land.

Nerites are primordial snails with a thick-walled half-oval shell, whose few whorls expand fast to the diameter of the aperture. Additionally they tend to melt with growing age so the snail then is hardly recognisable as such. The pattern of dots and stripes is so variable, a species from different regions can hardly be determined except by their characteristic operculum, the shell lid.

The preferred habitats of the fresh water nerite are large flowing waters with hard underground. Here the nerite lives on diatoms - silicate algae. To eat the contents, the nerite has to crush the diatom's hard silicate armour on the ground. Nerites breathe using gills. They have separate sexes and lay egg capsules on the ground, as well as on other gastropods' shells.

Concrete constructions on water flows, as well as water pollutions have deprived the nerite of its feeding sources, so that today it is found on the red lists of endangered species. For that reason the common fresh water nerite has been selected ?Mollusc of the Year? in 2004. Other species of fresh water nerites are the Danube nerite (Theodoxus danubialis) and the striped nerite (Theodoxus transversalis).

Common Mud Snail and Acute Mud Snail

In contrary to the nerite snail the mud snail has got a bulbous shell coiled in a classical snail's spiral, whose aperture, like a nerite's, is closed, if need be, by an apertural lid (operculum). Mud snails belong into the  Ampullariacea superfamily, they are related to the tropic apple snails (Ampullaria) kept in fish tanks.

In Europe there are different Viviparus species, most of which live in the flowing waters of lowland rivers and on the banks (littoral) of large lakes. Only the acute mud snail (Viviparus contectus) also lives on the floor of large lake rich in plant growth, in ponds, backwaters and in swamps.

Mud snails are herbivores; they eat plants from the water floor. Mud snails breathe using gills. From their breathing water they can also filter nutrients, like a mussel does. This is why at a place rich in nutrients they sometimes stop and rest for a longer time.

On the search for food juvenile acute mud snails (Viviparus contectus) crawl hanging uside down from the water surface, like pond snails (Lymnaeidae) do.

The frontal part of a mud snail's head is elongated to a prominent proboscis, left and right of which are the two tentacles. To feed, the mud snail, like other snails, uses its rasp tongue (radula) to rasp food from the ground.


  J. Ramsauer: Radulae - Electron microscope picture from the Salzburg University, among others also of Viviparus contectus.

Mud snails have separate sexes ? among some species there even is a clearly visible sexual dimorphism, the female being much larger and their shell more bulbous than the male's.

The male mud snail's right tentacle is modified to a copulation organ. The mud snail's scientific name, Viviparus, is due to their bearing live young: Mud snails are ovoviviparous: Their young hatch from the eggs in the female's body and are born alive (see picture on the right). Juvenile acute mud snails (Viviparus contectus) have got long hair on their shells, which enhance camouflage by binding earth particles to the shell and thus concealing it from its environment.
     
Ovovivipary is a phenomenon that also occurs among certain land snail families (for example door snails, Clausiliidae). The difference to real vivipary, as found among mammals, is that the eggs are built, the young hatch, but all that happens in the female's body and the young are born only when the conditions are favourable.

Common Bithynia

The country of Bithynia can be found on the ancient peninsula of Asia Minor. It is located in the Northwest of today's Turkey, on the south coast of the Marmara Sea, between the Bosporus and the Black Sea.

Bithynias (Bithyniidae), owing their name to this ancient landscape, are well distributed on all continents, except on the Americas, where only Bithynia tentaculata has been introduced.

The oval or conical shell of a bithynia is closed by an operculum. Bithynias breathe using gills. Like mud snails, they as well are able to filter their breathing water for nutrients. Additionally they feed on decaying plant matter and other organic detritus.

Before laying its 20 to 40 single eggs, the female bithynia cleans the underground from stones, mussel shells and algae. Then with its foot, it arranges the eggs to a band of spawn.
Summary

Comparing the three species of fresh water gastropods, it is obvious, that they all breathe by gills and have an operculum at their foot tip. They only have two tentacles, at the base of which the eyes are placed. Their head is elongated to a prominent snout or proboscis. All described snail species have separate sexes ? there are sometimes very different males and females. As a special thing the young of a mud snail are born alive, though they hatch inside the female mud snail's body (ovovivipary).
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« Reply #1 on: June 01, 2010, 04:43:01 PM »

Snails Breathing With Lungs
(Pond Snails, Ram's Horn Snails, Fresh Water Limpets, Bladder Snails)


[Bladder snail (Physidae family) floating on the water surface's underside.]

Many other fresh water snails, though, do not breathe using gills. Their gills are reduces, instead leaving to the snail the thin wall of the mantle cavity to assimilate oxygen through. This organ is called the snails' lung, this type of snails is also referred to as pulmonate (lung) snails (Pulmonata). Those lung-breathing snails make, by far, the largest part of known gastropod species. The advantage of breathing with lungs is obvious: Those snails can breathe oxygen from dry air and do not have to rely on water.


[A lesser operculate snail (Hydrobiidae family) from brackish water, on the water surface's underside.]

To be able to do this, fresh water snails breathing with lungs have to regularly go to the surface. They climb plants or simply float to the surface. Some freshwater snails even are able to crawl on the lower side of the water surface, eat algae while doing so and breathe oxygen from the air. This is possible because of the water's surface tension, which makes it possible to a water strider to run over the water surface.

Not only pulmonate snails float at the water surface (apart from the Physidae in the upper left picture, it is for example also the Lymnaeidae and the Planorbidae), but also gill-breathing snails, such as the lesser operculate snails (Hydrobiidae, in the lower left picture), among which the behaviour might rather serve the purpose of finding food than of breathing.

Great Pond Snail (Lymnaea stagnalis L. 1758

Among those fresh water snails breathing with lungs, for example, are pond snails (Lymnaeidae). With up to 60 mm shell length the great pond snail (Lymnaea stagnalis L. 1758) is actually the largest land snail in Europe. In contrary to that are the largest European terrestrial snail, the Roman snail (Helix pomatia) with 50 mm shell height at most and the largest gastropod of all in Europe, which is a slug, the ash-black slug (Limax cinereoniger) with a body length of more than 20 cm or 8 in. (!)

[Great pond snail (Lymnea stagnalis) with bladder snail (Physella acuta).]

Pond snails have got an elongate shell that is often extended characteristically in the aperture area. They mainly live in calm waters such as ponds and backwaters, where they can graze plant matter and decaying organic matter (detritus). Compared to nerites, mud snails and bithynias, pond snails lack a proboscis, as well as an operculum. But then again, none of the pulmonate snails have one.

Ram's Horn Snail

The name ram's horn snail is because of the shell's resemblance with a ram's coiled horn. The scientific name, though, Planorbis, is due to the shell form (plan-orbis: Latin for a flat disc). And literally the spire of a ram's horn snail does not ascend, like in other snail shells, but remains plane, even receding into the shell's interior.

Among the family of ram's horn snails (Planorbidae GRAY 1840) there are also other ram's horn snails, but also the unusually formed river limpet (Ancylus fluviatilis, see below).

Most ram's horn snail species inhabit calm water rich in plants. They are also able to endure their home water falling dry for a certain period of time. In contrary to many other snail species, ram's horn snails have got red blood - their (like humans') blood pigment is haemoglobin. Aquarium keepers like very much specimens low in pigments, that look pink because of their blood shining through.

Looking at a ram's horn snail, one can see, that like a pond snail, it lacks an operculum at the foot tip. There are other snail species like the Colombian ram's horn snail (Marisa rotula), that look like a ram's horn snail, but in fact are not one. The have an operculum at their foot tip and besides are more closely related to mud snails.

[Ram's horn snail (Planorbarius corneus).]

Like pond snails, neither the ram's horn snail has got a proboscis, but clearly visible lips. Alike the former, its tentacles cannot be withdrawn and are two in number, eyes placed at their base. Ram's horn snails, like pond snails, are hermaphrodites, deposing their flat, disc-shaped egg-packets on plants and stones.

Some ram's horn snail species are also notorious for being intermediate hosts to dangerous parasites: The tropical ram's horn snail Biomphalaria glabrata, for example, is intermediate host to the blood fluke (Schistosoma mansoni) which is the cause for a sever tropical disease called Schistosomiasis or better known as Bilharziosis.

River Limpet
In spite of looking externally like a limpet, the river limpet (Ancylus fluviatilis) is more closely related to ram's horn snails, with which it shares a common family. There are, in fact, several snail groups, in which a limpet-form shell has evolved. Another, for example, is the lake limpet (Acroloxus lacustris), which belongs to another family.

Albeit its name, the river limpet does not live exclusively in rivers, but in all types of waters with a high oxygen content, such as the littoral zone of lakes, is fast flowing sections of rivers, from the source creek into the wide river areas.

[The river limpet (Ancylus fluviatilis) in spite of looking like one is not a limpet, but more closely related to a ram's horn snail.]

Acute Bladder Snail
Bladder Snails (Physidae) together with ram's horn snails (Planorbidae, s.o.) have in common their thread-like tentacles, other than, for example, the ear-shaped tentacles of a pond snail.

A bladder snail's shell only grows to about 10 mm height - the difference in size to a comparatively giant pond snail catches the eye. The last whorl of the shell is very much expanded, so its larger than all of the remaining spire. The bladder snail, like the snails mentioned earlier, does not possess an operculum.

The acute bladder snail prefers warm standing waters and has been widely spread into the rest of Europe coming from the South-West.

[Acute bladder snail (Physella acuta)]

Summary

Compared to fresh water snails breathing with gills, there are clear and obvious differences in the snail species described on this page:
    *  They do not possess an operculum.
    * They breath with a snail lung (in the mentioned river limpet that has even be reduced, the snail breathing only by cutaneous respiration, directly through the skin).

Keeping in one's mind, that especially smaller water bodies on the continents bear the imminent danger of drying out, the advantage of water-living snails breathing with lungs is obvious: The can also breathe oxygen from the air and so can also survive outside of the water, they might even cross some distance on dry land to reach another water body.

If they have to do so, there is also another advantage: Many fresh water snail species are able to auto-fertilise themselves to increase the number of individuals in their population (see. for example: Pond snails).

Ass well, though, like all other water-living snail, pulmonate fresh water snails have only one pair of tentacles, that are not retractable and at the base of which the eyes are placed. They are therefore called Basommatophora or base-eye snails. In contrary to that, there is another large group of snails, making the largest part of land snails, is called Stylommatophora (literally the stalk-eye snails or terrestrial pulmonates). Those have eyes at the tip of a second, longer, pair of tentacles, all of which can be withdrawn. All those lung-breathing snails are grouped together as lung snails or pulmonates (Pulmonata).

This revolutionary breathing method, and the ability resulting from it to adapt to many more living places than gill-breathing snails, has led to pulmonate snails' species number by far prevailing all of the snails and finally all of the molluscs.

Among the stylommatophorans, for example, are amber snails (Succineidae). This snail family never lives far from the next pond, a fact that has led to the false assumption of them living amphibious. But amber snails only often live on plants near the water, but never in it. There they graze algae or other plant matter. Like pond snails, amber snails also may perform auto-fertilisation to increase their population's head count.

Living in the nearest vicinity of water also bears many dangers for amber snails: Parasitic distomes (Trematoda), infecting a warm-blooded animal as terminal host, will pass a snail on their way in development. The snail eaten by a bird of mammal lead to the latter's infection with the distome's larvae.

[Amber snail]






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« Reply #2 on: June 01, 2010, 05:24:08 PM »

Here are some photos to go with the text.

Apple or mystery snail (Pomacea bridgesii sp.) Light


Apple or mystery snail (Pomacea bridgesii sp.) Dark


Small ramshorn snail (Planorbis or Helisoma sp.)


Columbian ramshorn snail (Planorbis or Marisa sp.)


Malaysian trumpet snail (Melanoides tuberculatus)


Snail Management And Control
Snails....love them or hate them they are an extremely abundant and popular addition to the hobby. Some species of aquatic snails can be of benefit in an aquarium, by consuming waste such as left over food, dead bodies and dead leaves.
If you are one of the many people who would like to cut down the population of snails in your aquarium or attempt to eradicate them then here are a few things you can try.

Where did they come from?
Snails can be introduced a number of ways. The most common snails that are referred to as nuisances are the Malaysian Trumpet Snail (MTS) 'Melanoides tuberculatus' and Ramshorn snails 'Planorbis corneus'. The most common method of introduction is either via plants or substrate. Snails may lay eggs on plants and also in the substrate, often going unnoticed by the aquarist until they reach a distinguishable size and start coming out looking for food, This is often the case when using second hand gravel or adding plants from tanks with snail populations. If you have a live bearing variety of snail (MTS), then you can get it in the bag of fish where the fish were caught in tanks with this snail.

Why are they so prolific?
Snails do not always live up to their bad reputation, it is possible to have a tank with snails and keep their numbers under control. The number one trigger that will cause snails to get out of control is over feeding....this is almost always the case. If an abundance of food is available to the snails then you can rest assure that they will condition themselves up for breeding......excess food also aids the young snails fast growth rate. Live bearing snails such as Malaysian trumpet snails generally hide and bury themselves during the day and are seen most active at night, they often go unnoticed for long periods of times because of this and by the time they have populated your aquarium it's too late. Ramshorns are most active during the day and are an egg layer, they are one of the most common snails to hitch-hike in on plants.

Methods of removal:

Natural: Snails love vegetable matter and algae wafers. By simply placing a small piece of zucchini or an algae wafer in the aquarium you can manually remove them, the food acts as an attractant and brings a vast majority of snails out of hiding......whilst they are having a feast you can net them out of the aquarium and dispose of them correctly (do not expose them to our waterways please) This method is tedious and often is a temporary fix to the problem.

Traps: Snail traps can be either commercially purchased from your LFS or home made. Some are better than others so trial and error works best in this instance.
Most work by placing a piece of food inside the trap and having some form of 'one way entry' system....once they are in and have collected the bait it is very hard for them to escape. This can be left in overnight to catch most inhabitants and generally requires at least 3-4 attempts to get most of the snails... but not all. These traps are best suited to tanks that do not have small fish as the fish like to get into the traps.

Chemical: Snail eliminators come in a liquid form and are added directly to the water column, they contain a lot of copper so care must be taken when dosing the aquarium with them. In most situations they should only be used when you have a Kh reading of at least 4? or 71.6ppm.....use only as directed. All invertebrates and plants are sensitive to copper and so are some species of fish, so read the instructions carefully and use only as a last result or whilst no fish are present in the aquarium. Remove any activated carbon while treating.
If you do not wish to use a chemical, and you do not have any fish or plants in the tank, then you can use large quantities of normal salt.

Biological Control: Some species of fish such as Clown Loachs Chromobotia macracanthus and the Yo-Yo loachBotia almorhae will often hunt down snails and control their numbers. They will never eradicate them completely but will aid in the process. In African cichlid tanks Chilotilapia rhoadesii can also control snail populations. Biological control should only be considered if the fish suits your water parameters and you can accommodate them long term.

Prevention: Prevention is always better than cure! If the food source for the snails is limited, the population will reduce itself to more reasonable numbers. In aquariums when there are a lot of adult snails in the tank, they produce chemicals (pheromones) that reduce the hatching and/or growing of new snails. Take away these adults, and there will be another explosion in numbers until a more sustainable population is reached. In other words, ignore them if you can, and they will dwindle in number in their own time. I personally add snails to my aquariums and have never had a bad 'outbreak'. In the mean time, they are eating various waste products in your tank, including algae and dead leaves (particularity Malaysian trumpet snails) , and recycling them in the gravel for your plants......the aquatic earth worm!

Source : http://www.perthcichlid.com.au
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« Reply #3 on: June 01, 2010, 06:38:24 PM »

How to reduce the amount of shellfish.
Although the shells are even better. But if the amount would not be suitable lot to like in the pond snail mentioned above. Shell will generate well in hard water and the pH. Because snail shells can not stand the acidity and makes it soft shell. The so sometimes it can break and cause the death. Then we come to the same elimination.

Reduce food
Some conditions may be found in snail breeding tank without knowing why ... The main fact is that feeding too much .. Did you know that the remaining fish food. The snail is good food ever. Get the complete nutrients like viagra. The snail increase rapidly How simple is the waiting time to eat fish. If not, within 3-5 minutes. Show that you are feeding too much. Should be in very small amounts. But often better to throw it at each lot. Hope that moment it will be hungry to eat more food if left out Let it suck.

Snail hunting
Another reason is the increase in shell volume cabinet. Is the lack of hunting in the ecosystem.
In nature they will be snail control volume by all hunters.
Dwarf puffer and large puffer living with eating snail mainly.
Including Botiidae(Loach fish) family such as Botia almorhae, Yasuhikotakia sidthimunki.
Recommended to large puffer better than Dwarf puffer  because it will eat a big snail to the shell.
It will spit out a few snail shell fragments.
But Dwarf puffer, it will take to snatch the shell face. Then suck the snail out private.
Allowing time to get rid of it. And Snail shells and fragments to be much cleaner than.

Cooked vegetables.
That the spinach or cabbage to boiling. Then tie with string. Buried under timber
Prior to that rock off light then all snail will come out to eat cooked vegetables that
At the morning before the light. Bring out the vegetables with attached snail.
Do this until the amount of consecutive snail less, in case the big tank put many points will be removed faster.

Drug elimination snail
The last way is not recommended. Because it is harmful to fish or shrimp in the tank.
If someone would have to be at a loss just this way.
Do not forget that the drug would eliminate bacteria in the filter.
Be careful to follow label side box If unsure, put a half dose. Then add later.


Source : http://aqua.c1ub.net
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gzaqs27334
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« Reply #4 on: September 30, 2012, 05:48:34 PM »

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