Snail... evil or not?

The carnation is a long story, however it didn't cost me any money. I expect it to die. I will not pollute my tank to try to keep it alive.

 

Is this the site?

The Sea Slug Forum - Species List

It's going to take me forever to go thru all those pics!

 

That's a pretty awesome little snail. No need to look through the Sea Slug Forum species list, I don't think, unless it incidentally got there as one of the "not a slug" species. I REALLY would like to see some close-ups of the snail, and as the others suggested, see what it looks like if you make it retract the mantle (after you poke it). Can you catch it and photograph in in a dish?

The lower photo shows a foot that is very similar in shape and pattern, if different in color, to a velutinid (or at least, velutinoid) that I collected and photographed, and tentatively identified as Trivia oryza. The problem with the ID's on the net of that species is that there are a whole bunch of very similar species in the family, and you just about have to kill the animal and examine the shell under magnification to tell the difference. The live-animal pics that I've seen which are purported to be that species have more of a pattern of straight white lines on the back of the foot rather than the radiating pattern like yours (and mine). Mine had pastel lavender lines where yours appears to have bright magenta lines. However, when I look at the first pic, it looks like a regular snail with a regular spire, rather an an egg-shaped shell like the cowries and Trivias. If it has a pointed spire, it's not a Trivia, although it might be a relative.

If you had just described it to me, I would have been sure it was an ovulid. They feed on soft corals and gorgonians, and almost always closely match the color and pattern of the prey species. It still might be that, but I can't tell for sure from the posted photos. It would be quite a coincidence though, if an animal in a different family had a foot so similar to the Trivia species, but...I guess it could happen.

Chances are around 100% that it's not beneficial to its host, although it might not be hurting it either. It's only going to be symbiotic in biological sense of living together with its host, not in a traditional, mutually beneficial sort of way. Chances are probably better than 50% that it's actually feeding on the host.

I could keep musing, but I guess I'll wait and see if you can get some more photos of it. The more angles the better

Cheers,



Don

 

Okay, it had taken up residence in the crevices of a powerhead which I removed, looked in at the "snail" and it was shiny and didn't have the white tentacles coming off of it. I shook it out and here's what it looked like, very smooth and a kind of brownish pinkish color, striped. This thing was very hard to take pics of, as for the size, I'd say about 1/4 of an inch or a bit smaller.







As it sat in the dish it started to turn the bright pink color again, like it was in the first pics I posted earlier today, with the tentacles. The following pics show the progression of the color change until it finished. Some are from the bottom side too. At the end I poked at it, touched it, pushed it around and it didn't change shape/color/size.

 

Update:

I just had to manually remove it from the dish it was in (because I put it back on the carnation) and it turned into the shiny thing again. I guess I didn't agitate it enough the first time.

 

Yep, it's an ovulid, probably a Prionovolva or Primovula species, and is feeding on your carnation. They are notoriously difficult to ID to the species level, but I'll work on it and see how close I can get.

Cheers,



Don

 

Hmm, there are several Prionovolva species that are banded and simlar, but yours appears to have a yellow background. I have some live animal photos at home, but I'm away for a few days, and can't seem to find any good ones on the net...maybe this one, Pseudosimnia culmen?

http://www.cowries.info/sale/ovultriv/ov5.jpg
Cypraea Cowries Cowry Seashells Cypraeidae Felix Lorenz shellauction

I'll keep looking and see if I can find a matching live animal photo.

Cheers,




Don

 

Here's a photo claimed to be that species by the photographer. May be pretty close:

http://www.daveharasti.com/nelsonbay/seaslugs/cowries/Pseudosimnia_culmen.jpg

I'd rather compare to Felix Lorenz's photos, since he's so careful with his ID's, but his pics are apparently offline. I'm hesitant to rely on ovulid ID's by photographers since they seem to be wrong about 90% of the time, but this one should be useful for comparison at least.

Cheers again,



Don

 

That looks just like it! The stripes are a bit more defined however I'm sure they can vary quite a bit. Thank you so much! I think that is so cool that you are able to ID something like this. Do you study these or something? How does it change like it does? That is so crazy!

 

I just found another one. I'm wondering if I should remove them...? If it's feeding on the carnation, will it feed on my other corals as well? I'm going to start googling!