Thing Growing on Shells....

Can anybody tell me what this is? Is it a snail? It grows only on my hermit crab shells and seem to grow pretty fast. The "thing" under that shell is white w/two antenna, from what I can see when it lifts it shell a little (hard to see though).

 

Oh you see them at the sea side all the time. PagoJoe will be able to tell you what it is. PM him

 

I can't see the pic but maybe barnacles.....

 

+ to barnacles. that what it looks like to me

 

So are they bad for my tank? I have a FO tank with some shrimp/hermit crabs, no LR or corals.

 

No es un barnacle, it's a Crepidula, Crepidula fornicata I believe. Linnaeus name 'em that because they are often piled one on top of the other, and look like they are..fornicata-ing. They are harmless.

Crepidula (Ianacus) fornicata

Cheers,



Don

 

WOW! Thanks! So how do these things hitch a ride? I only recently (like within the last month) have noticed them. I haven't added any fish in a couple months and none of my hermits shells had these on them when I bought them (also purchased several months ago)......

But yeah, thanks for the ID, they look exactly like the pics in the link and seem to grow really close to each other.

 

They usually hitch a ride when they are very small. The larval form of the animal will settle on the shell, and it will stick there. Then, as the Crepidula shell grows, it conforms to the surface that it settled on, like some of the limpets do, and pretty much spends its life there unless it's dislodged. In areas where they are common, you'll often see globs of them piled on top of each other, with one Crepidula shell conforming to the shape of another Crepidula shell, just like yours has conformed to your hermit's shell.

Cheers,



Don