Are these predatory whelks?

[ak4890]

Got these at my local fish store — had about 10 trochus snails in my tank, but almost all are dead now. Initially assumed predation from hermit crabs but now not sure — what kind of snail are these? (I asked for ceriths and got these, are these Nassarius, whelks, or something else?). They seem to have done fine for a very long time when there were no other snails in the tank, and so I assumed they were algae-eating snails.

 

[Ron Reefman]

As far as I know, ALL welks are carnivores. And this is based on experience as I collect a lot of animals for my tanks here in SW Florida.

 

[ak4890]

As far as I know, ALL welks are carnivores. And this is based on experience as I collect a lot of animals for my tanks here in SW Florida.

Got it..do these look like whelks?

 

[Ron Reefman]

That's a tough call based on those photos. It could be a young whelk, but I can't say for sure.

Any chance you could pull one out of the tank and get better photos of it?

 

[GlassMunky]

no i dont believe those are welks. i HIGHLY doubt a lfs would sell you predatory snails.]
They look more like Turbo snail shells to me.

Whelks tend to have a longer and more conical shell like this.

 

[GlassMunky]

Whelks also have a proboscis that they will hold up high, these dont seem to have that.
Heres an article on them

Whelk versus Nassarius | Melev's Reef

melevsreef.com

 

[ISpeakForTheSeas]

Any chance you could pull one out of the tank and get better photos of it?

+1 to some more pics under white light - preferably straight-on pics of the top and sides. Clearer pics of the proboscis and/or mantle would also be helpful if you can manage it.

 

[ak4890]

Hi Everyone, thank you again for all the help — here's some (hopefully) slightly better pictures of one of the snails. They're about 0.75"-1" in size lengthwise, and they do have a proboscis that sticks out in front.

 

[Ron Reefman]

It's still hard for me to say. It looks a bit like a young crown conch. And while they aren't strictly carnivores, they do eat other critters.

But that ID is far from definitive.

 

[ISpeakForTheSeas]

I'm not entirely sure (it's hard to see the shell under the algae), but I'm thinking it may be a Rapanine Whelk of some variety:

The best I can do is narrow it down to most likely being in the taxonomic Subfamily Rapaninae (the Rapanine Whelks) - this subfamily includes the Mancinella genus, and a few other genera that have species that look at least superficially similar to this as well, such as Acanthais, Drupa, Menathais, Neothais, Plicopurpura, Reishia, Stramonita, Thais, and Tylothais.

Depending on the species, Rapanine whelks may eat worms, snails, bivalves, small crustaceans, and reportedly sometimes small fish; snails, bivalves, and worms are the more common prey.

 

[ak4890]

I'm not entirely sure (it's hard to see the shell under the algae), but I'm thinking it may be a Rapanine Whelk of some variety:

Depending on the species, Rapanine whelks may eat worms, snails, bivalves, small crustaceans, and reportedly sometimes small fish; snails, bivalves, and worms are the more common prey.

I tried to get a slightly better picture of the outside of the shell — thank you so much for the ID though! Does this help at all?

 

[ISpeakForTheSeas]

I tried to get a slightly better picture of the outside of the shell — thank you so much for the ID though! Does this help at all?

It makes me feel more confident that it's either a Rapaninae or Ergalataxinae species, likely one of the "Thaidid" species in one of the two subfamily. There's a lot of taxonomy issues with at least the Ergalataxinae subfamily, and a lot of the specimens share a number of at least superficial characteristics with their Rapanine cousins.

Regardless, some genera with similar looking species to this, and some specific species you can compare with:

(Rapaninae)
-Menathais (M. intermedia)
-Reishia (R. clavigera)
-Thais (T. hippocastanum;* this scientific name isn't valid, and is considered to actually be Volema myristica - your snail is definitely not V. myristica, but a number of the pics you can find searching for T. hippocastanum are definitely mislabeled; I'm not entirely sure what species it actually is - it may be M. intermedia again, but it looks similar enough that I thought I'd list it)
-Tylothais (T. virgata)

(Ergalataxinae)
-Tenguella (T. granulata & T. musiva)

M. intermedia or T. virgata would be my guess for your snails, but I don't know for sure (and you may have multiple different species).

If they are one of those two, they are murex snails (family Muricidae), so while not true whelks, they are predatory, most likely against other snails and bivalves (clams, oysters, scallops, etc.). As mentioned, they may also eat worms. Some closely related species also eat corals, but I doubt that would be an issue with these.

Either way, these would be cool sump snails, but they will likely eat your CUC if kept in your display.

 

[Troylee]

I’ve never been able to tell apart a welk or nassi but those being on rocks tells me it’s most likely not a nassi as they live in the sand and only come out for food and back in the sand! I’ve never seen any of mine on rocks and only on the glass to lay eggs.

 

[ak4890]

It makes me feel more confident that it's either a Rapaninae or Ergalataxinae species, likely one of the "Thaidid" species in one of the two subfamily. There's a lot of taxonomy issues with at least the Ergalataxinae subfamily, and a lot of the specimens share a number of at least superficial characteristics with their Rapanine cousins.

Regardless, some genera with similar looking species to this, and some specific species you can compare with:

(Rapaninae)
-Menathais (M. intermedia)
-Reishia (R. clavigera)
-Thais (T. hippocastanum;* this scientific name isn't valid, and is considered to actually be Volema myristica - your snail is definitely not V. myristica, but a number of the pics you can find searching for T. hippocastanum are definitely mislabeled; I'm not entirely sure what species it actually is - it may be M. intermedia again, but it looks similar enough that I thought I'd list it)
-Tylothais (T. virgata)

(Ergalataxinae)
-Tenguella (T. granulata & T. musiva)

M. intermedia or T. virgata would be my guess for your snails, but I don't know for sure (and you may have multiple different species).

If they are one of those two, they are murex snails (family Muricidae), so while not true whelks, they are predatory, most likely against other snails and bivalves (clams, oysters, scallops, etc.). As mentioned, they may also eat worms. Some closely related species also eat corals, but I doubt that would be an issue with these.

Either way, these would be cool sump snails, but they will likely eat your CUC if kept in your display.

Thank you so much for the very detailed response! I think it might almost certainly be Tylothais virgata — about to move them to my sump! Lost another turbo this week, so they're definitely at it