What Do We Know About Nerite Snails?

[Anna]

Hello Everyone

I am a fan of freshwater nerite snails, having kept Neritina turrita, Clithon brenspinas, and Septaria porcellana, plus the thorny type, for some time. I am now writing an article for other fishkeepers about these species, but I have found it almost impossible to get good information. I obviously have practical experience of looking after them in aquaria, but what I really needed was scientific details.

All I can find out is that the family Neritidae are prosobranch gastropods, mainly intertidal marine types but some in freshwater. I can find nothing out about the specific species I keep – not even which part of the world they come from (Indo-Pacific?), or the correct scientific name for the thorny type. Are they all gonochoristic? Do they all have veligers which grow up in the sea? Do the eggs hatch in freshwater and the young just die off without being seen, or do the egg capsules not open without salt? It sounds like some of the people on this site have raised Theodoxus spp. without any salt at all? So what is the natural habitat?

I have trawled through the last 100 years of the Journal of Molluscan Studies, searched the internet exhaustively, and even spoken to the British Library. There is one book I know of in English that might help (The Ecology Of Freshwater Molluscs), but it costs around £100 to buy and I can’t really afford this, seeing as it has only one page on the Neritidae in the whole book! I have read through the posts about nerites on this site, but there are only snippets of information. Does anyone know of any scientific papers I might have overlooked, or any books with basic info on the nerites? Or does this information just not exist at the present time?

Many thanks,

Anna

[badflash]

I'm nt going to be much help. Non-Pest snails are one of the most under-studied animals out there. I keep olive nerites. but I've not done any science on them and also could find nothing published about them.

Sounds like an opportunity to do a pHD.

[pleco_breeder]

Hello,

I'm traditionally not a "snail person". A better way of stating it is I'll pitch a tank in the trash if I find one in it. However, I did manage to find this hobbyist page which references several journals and scientific papers. The article is probably not going to help much, but the references appear to be credible.

http://www.reefkeeping.com/issues/2004-06/rs/index.php

Hope this helps,

Larry Vires

[Anna]

Hi Larry

Thanks very much for this. I searched the internet for two days straight, so I don't know why my search engine didn't pick this page up!??!

I understand how you feel about snails, but they really can be very cute in a comical way - much like plecos . . .

Anna

[Allex]

It sounds like some of the people on this site have raised Theodoxus spp. without any salt at all? So what is the natural habitat?

Hi
I've raised and successfully bred european nerite Theodoxus fluviatilis in freshwater, without any saltwater stage at all. They live in rivers and lakes with gravely bottom, where they feed mostly on diatoms. Easy to breed in hard alkaline water.

[Anna]

Hi Allex

That's fascinating. I've read that T. fluviatilis is found in lakes, but I always wondered if this was a misidentification, because it would be impossible for youngsters to reach the sea. And I know the eggs still develop in sea water. Would you mind telling us how you raise the young? Do you find them visible to the naked eye? How long does it take for the eggs to hatch - I have read about a month? I have heard you only get one youngster per egg? And can you tell the sexes apart?

Sorry to ask so many questions!

Anna

[apistomaster]

Hello,

I'm traditionally not a "snail person". A better way of stating it is I'll pitch a tank in the trash if I find one in it. However, I did manage to find this hobbyist page which references several journals and scientific papers. The article is probably not going to help much, but the references appear to be credible.

http://www.reefkeeping.com/issues/2004-06/rs/index.php

Hope this helps,

Larry Vires

That makes two of us. As fish breeders of fish that lay eggs with long incubation periods snails can devour and otherwise good spawn.
This isn't a major problem with plecos that have a male diligently guarding and cleaning eggs but snails can harm Corydoras eggs. I wouldn't have thought so based on how tough shelled their eggs are but a radula embedded with thousands of "teeth" apparently eventually can eat the eggs.

Only a couple of snails can destroy a spawn of delicate eggs laid by Characins, Cyprinids and Killifish.
Dr Robert Goldstein in a pm tells me a pinch of fluebendazole added to the tank will kill snail and Hydra. Finding powdered flubenazole is easier said than done, however. He siad it has never harmed fry and that in geneal it is a substance with very low toxicity. It is highly toxic to invertebrates so don't try this in your shrimp tanks.

[Allex]

I've read that T. fluviatilis is found in lakes, but I always wondered if this was a misidentification, because it would be impossible for youngsters to reach the sea.

Yes, this would be impossible, but they really live and breed in lakes. This is where I found my snails 3 years ago.

And I know the eggs still develop in sea water.

I have no idea if they develop in sea water, but normal freshwater seems to be enough. Ph is around 7-7,5, GH = 8,5-9 KH = 4-4,5 (but I think this could be a bit too low, because of the shell corrosion and dissolution in older specimens).

Would you mind telling us how you raise the young? Do you find them visible to the naked eye?How long does it take for the eggs to hatch - I have read about a month?

Yes, they hatch after a month or so. They are a smaller version of their parents and eat the same algaes (Diatoms). I haven't recognized any larval stage at all (they seem to hatch fully developed). After hatching their size reach from 1 to 1,5 mm.

I have heard you only get one youngster per egg?

Yes, this is true, but the "egg" is really a cocoon with multiple eggs inside thou.

And can you tell the sexes apart?

Only when they're mating, the male has a long flexible "tentacle" (sorry this is the best description) on one side of his head (I'm not sure if this is on his left or right side). The male inserts his appendix inside the females mantle cavity. The whole act takes a few minutes.

A few weeks old snail


A mature snail


A snail carrying an "egg"


A few minutes old young (size 1 mm). cocoon still visible.


A few weeks old specimen

[Anna]

Hi Allex

What great pictures! I loved the one of the new-born snail with the egg. Thanks very much for answering my questions.

Anna

[JK]

Hi Allex,

How big are your adults?

[ToddnBecka]

If I remember correctly, that species grows to about pea-size. It's a shame they don't grow as large as olive nerites.

[badflash]

The largest of the true fresh water nerites only get to be about 10-11mm.

[Egnom]

Hello

My name is Rui Monge and I´m from Portugal. I have collected some Theodoxus sp. from the Guadiana river here in Portugal and I have been reproducting these freshwater snails in my tanks. However, the padron of their shells are a bit diferent from the ones here shown in this topic.
They have been colected in freshwater, however, they also occur in the brackwish part of the river.
One interesting thing is that some of the snails I collected in the wild present shell damage, but others don´t. I don´t no why this happen.

I´m sorry for my bad english... Here are some pictures that a friend of mine took, of the snail´s shells I caugth in the Guadiana river:
















This is an adult and a juvenil born in my tanks, near a coin, so we can compare the sizes:



Here in the Portuguese Forum we have been debating this specie:
http://www.aquariofilia.net/forum/index ... 98813&st=0
And also in here:
http://www.applesnail.net/forum3/viewto ... 30&t=17572