Are Nassarius Snails Predatory?

[1F2FRFBF]

I've had a couple strange experiences with my snails over the past couple days - or maybe it's not so strange. Maybe someone with a bit more knowledge can shed some light on the subject.

I have 8 Nassarius snails that I purchased about a week ago. A few days ago I added some black turbos, mexican turbos, cowries and ceriths. The next evening I saw one of the Nassarius trying to climb on one of my black turbo snails. I watched for a bit, and it almost looked like the Nass was trying to get to the turbo underneath - not just climbing over it. So I stuck my hand in, picked up the turbo and moved it to another section of the rocks. Much later, before I went to bed, I shined the flashlight in the tank to see how everyone was doing, and I saw that several of the Nassarius had climbed up into the rocks. I couldn't see what had their interest, but I'm pretty sure I got a glimpse of the turbo's shell.

Now, today I introduced some Stomatellas to the tank, and not too long afterward we noticed about half a dozen of the Nassarius in what could only be described as a feeding frenzy on the sandbed - tumbling over each other and trying to knock each other senseless. When I looked closer I noticed that they were attacking one of the brand new Stomatellas. Now there's just an empty little shell on the sandbed.

Moments later, after remarking that I hadn't seen any of the Nass bothering any of the other Stomatellas, I watched as one Nassarius chased a Stomatella up the front glass, overtook him, ripped him in half, and then went after the remainder.

I thought that perhaps the turbo and the Stomatellas might have been ailing in some way. Would they hunt down an animal that was ill or wounded but still alive? Everything I read about Nassarius snails led me to believe that they were scavengers and were not predatory.

I haven't seen them go after any of the other snails so far, but I'm really wondering if I want these things in my tank.

[reefnetworth]

your snails are hungry!!! more like starving. they clean each others backs off for food. research, before buying any saltwater creature. BTW you have to many snails!!!
JDM...

[1F2FRFBF]

Too many Nassarius, or too many total?

According to the buying guidelines I see, I have 1/3 as many as I "really" need.

[graveyardworm]

Are you sure that you introduced Nassarius snails? Can you post a picture? Alot of predatory whelks look alot like Nassarius.

[1F2FRFBF]

I'll get a pic for you when the lights come back on - I know it's something about the shape of the shells, yes? I'll look for images of predatory whelks in the meantime, though. Thanks.

[graveyardworm]

Pics of whelk shells can be found at Hardy's Internet Guide to Marine Gastropods. Click on thumbnails for pics. You'll see that Nassarius are in the same Genus as the whelks, There are alot of Nassarius, but only a few are commonly available in the hobby.

[pagojoe]

Heh, it may be a whelk, but it won't surprise me if it's a hungry Nassarius. A few weeks ago someone said you didn't need to feed Nassarius snails, since they are scavengers/detrivores. As I said then, unless you have a lot that needs scavenging, or very few Nassarius in a big tank, you probably need to feed them. One or two diced frozen shrimp a week should be enough to reduce the chances that they'll try to create their own carrion for scavenging.

Looking forward to seeing a pic of your snail,



Don

[pagojoe]

By the way, Stomatella snails have the ability to autotomize, or drop the back half of the foot, when they are being pursued by a predator. That may have been what happened first, when it looked like he was ripped in half.


Don

[reefgrief]

Ok.. how many snails are too many..?

I have seen suppliers advertise cleaner crews.. and they suggest as many as 2 to 4 snails per gal ( turbos, nassarius, and others)

Are there any authoritative documentations, or are their suggestions just exploiting ignorance ?

[pagojoe]

I think that's way too many, if you are talking about the great big snails. You would probably be fine with 100 little Nassarius vibex or Nassarius horridus in a 55 gallon tank, but even that seems a bit much. It would take a lot of leftover food to feed a hundred small Nassarius.


Don

[romunov]

Nassarius Snails as Scavengers in Reef Aquaria

[1F2FRFBF]

Romunov - I did read that article; it's what made me decide to avoid hermit crabs in my tank.

Anyway, here's one of my snails:



I asked one of the employees at my LFS yesterday about the snail numbers as well, and he said that he personally has two Nassarius in a 120G tank.

[1F2FRFBF]

Originally posted by pagojoe
By the way, Stomatella snails have the ability to autotomize, or drop the back half of the foot, when they are being pursued by a predator. That may have been what happened first, when it looked like he was ripped in half.
Don

Yep, that's what must've happened, because once the back half dropped off the front half kept on chuggin'.

[pagojoe]

That's the species I figured you had, since these big guys seem to be offered for sale a lot. Best I can tell, it's Nassarius arcularius. It's one of the species often called Super Tongan Nassarius, which seems curious since it's primarily an Indian Ocean/far Western Pacific species. I've collected fairly extensively in Tonga, and never seen one there. I'd guess that these big guys are a lot more likely to create their own carrion than the smaller species.

Dr. Shimek's article on Nassarius was great, but you should realize he dealt with two Atlantic species, and not everything that applies to the ones from this area applies to the ones from the Pacific. While most of the Nassarius species are sand dwellers, a lot of them spend their time embedded in algae on rocks, or crawling across it. These species usually have algae growing on their shells, while the ones that stay buried in sand are the glossy ones. I've seen several pics of Nassarius snails on this forum that have the algal growth, and they are some of the same species I kept in my tank. I don't think any of them would kill another animal in preference to eating something that was already dead, but they certainly might if they were hungry enough.

http://www.gastropods.com/0/Shell_160.html

Cheers,



Don

[graveyardworm]

As far as stocking, my 6 foot 100g tank with a DSB will only support about 10 of the smaller ones, but I have a lot of other scavengers as well. I feed that tank fairly heavily.

So based on the footprint of the sand bed I would recommend about 1 or 2 per square foot of sand bed.

[pagojoe]

Originally posted by graveyardworm
As far as stocking, my 6 foot 100g tank with a DSB will only support about 10 of the smaller ones, but I have a lot of other scavengers as well. I feed that tank fairly heavily.

So based on the footprint of the sand bed I would recommend about 1 or 2 per square foot of sand bed.

That sounds about right to me, a lot more reasonable than the fish store estimates.



Don

[1F2FRFBF]

Don, thanks so much for the information on the snails. It was a big help. Believe me, I try to do as much research as possible before adding anything to the tank because I don't want anything to suffer. I only have one fish right now, so there's not a lot of bioload there, and knowing this I was making sure to drop some food in the tank every day until I increased the fish population. Either it was enough and the Nass preferred munching on juicy little Stomatellas (and one black Turbo), or it wasn't enough and they were so hungry that they grabbed the first morsel(s) they could overtake easily.

One thing, though - I did drop some food in while they were attacking the Stomatella to try to divert their attention. A few broke off to go after the food; the others stayed and finished the snail feast. The one that went after the Stomatella on the glass did so while that other food was in the tank.

I did on several occasions find my Nassarius up on the rocks as well, but never noticed them eating any algae. They always buried themselves in the sand eventually.

Anyway, I think the best course here would be pulling those Nassarius out of my tank and trying to find the smaller variety - and fewer of them. I'll study the pictures and make sure I get the right variety.

Thanks again for the info - much appreciated.

[delsol650]

Thats a typically benificial tongan nassarius.. the black ones with a different part on its siphon part on its shell is the predetory type.. they also have a tattoo type looking pattern on their siphon.

My TBS shipment came with tons of these things.. spent a couple months ridding my tank of these things...

[madadi]

i got does same exact snails. they tried to eat my lettuce nudibranches as soon as i put them in the tank. they sure move and act like a nessarius but dont eat like one!! be carefull with them. i put mine in the sump

[jdieck]

I have had super tongan for a couple of years now, they have un uncanny ability to detect sik or dying critters and they will make up with it in just minutes.
They never attack a healthy critter. I feed them some sinking pellets once in a while.

[pagojoe]

Originally posted by jdieck
I have had super tongan for a couple of years now, they have un uncanny ability to detect sik or dying critters and they will make up with it in just minutes.
They never attack a healthy critter. I feed them some sinking pellets once in a while.

That's a good observation about what's gone on in your tank, but a pretty broad generalization following your observation. I'm not at all sure that "sick," "dying," and "vulnerable" don't smell the same to Nassarius arcularius. (Do stress chemicals from sick animals and stress chemicals from animals being transferred to new tanks smell the same to them?) It very well might be that your Nassarius snails never got very hungry, or that you never had the most vulnerable prey species in your tanks. There are plenty reports on the internet of these snails occasionally attacking animals that were apparently healthy. (When a Harpa snail or Stomatella snail autotomizes its foot, the snail is still healthy, but the effect is the same as if you chopped half its foot off, and the same body fluids will enter the water.) I've personally seen the difference in behavior between well-fed Nassarius snails and starved ones, and the starved ones become noticeably more aggressive. That's why I said it wouldn't surprise me at all if this large species creates its own carrion when it's starving.

Cheers,



Don

[jdieck]

Although they will not attack healthy ones weak or injured animals which may otherwise recover get attacked.

[Mac Inger]

Yep,..my nassarius just ate a margarita today.

I had never seen it happen either but they jumped on the guy. He must have been dying because the last week he was moving very little.

I shoo-ed the nassarius off and put the little margarita upright,...but when i got back from work he was only a shell of his former existence : )

[1F2FRFBF]

OK, looks like we need to suggest a new name for "Super Tonga Nassarius".

My vote is for "Super Flesh-Eating Mince-Meating Havoc-Wreaking Gastropods from the Depths of Hell".

[carlos_fb]

I have 10 black ones in my 60 gallon and they are definitely predatory. I have seen them attack and eat turbo snails and just this weekend they ate my cleaner clam so it looks like they will eat whatever is available.