Good or bad snail?

[Falcn]

I have several of these appeared in my tank. They have a small 'skullcap' shell and are very mobile and quick. They tend to 'walk' by moving each half of the foot alternately. As you can see they have several tentacles not only from the head, but also from the sides and back.

I need to know if these are beneficial or not - (goody/Baddy)?

Any help appreciated

 

[charlesr1958]

Stomatella, a very beneficial algae grazer and a keeper!

A Hitch Hikers Guide to the Reefs

Chuck

 

[pagojoe]

What Chuck said. It's Stomatella varia, although it's an oddly colored one. Great pics, by the way. I very rarely see pics of these snails that are good enough to show whether the shell has striations.

Cheers,



Don

 

[charlesr1958]

Hi Don,

Off topic a bit, but I've noticed that these snails have a tendacy to drop the last 1/3rd of their foot when greatly disturbed leading me to wonder if doing so is a type of distraction for predators much like lizards do when they drop their tails. Those specimens that I have had do so do not appear harmed and in due time replace the lost section. I believe I have a photo of such a dropping in the snail section of my above linked webpage.

Chuck

 

[pagojoe]

Hi Chuck,

Yes, it seems to serve the same purpose. Sometimes they don't even have to be attacked to drop the back half of the foot: if you frighten one, and it's trying to run for cover, the rear part of the foot may remain stuck to the rock while the snail runs away without it. The Harp Shells, and maybe the Morum species as well, can autotomize the back part of the foot. They will do it if a crab is attacking them, then circle back around and capture and eat the crab as it's trying to eat the dropped part of the foot (or so the story tellers say). I've seen one cowry do it after being envenomated by a cone snail, and I've seen a couple of species of nudibranchs do it (Discodoris species).

I've seen your Stomatella foot pic, too. Looks just like the ones I used to find in my collecting bag

Cheers,



Don

 

[charlesr1958]

Thats all pretty wild, I mean for an invert to develop such tactics, but then again, its getting really hard to surprise me anymore with what can and does go on within the reefs.
I shouldn't confess to this, but I spent a great deal of time trying to figure out what species of sea slug or flatworm I had when I too found a Stomatella foot in my collecting bucket, took me forever to finally put two and two together...lol

Chuck

 

[Falcn]

Thanks Guys, much appreciated. I had noticed a 'dropped' foot too, that was probably going to be my next question ;-)

This is one of the babies in the tank. I have counted almost 50 so far. I captured this little guy and brought him out into a small plastic chocolate box to photograph him.

I might try and get some better photos of one of the big guys (1.5" or so).