What the Heck is that?! I dunno...

Little Lucy 27

New member
I have a hermit that has two long jerky little tentacles that come out of a tiny hole in the back of his shell...they retract fully as well...anyone know what it is? Is this his appendage or is a hitchhiker inside his shell...lol...does it need to get out? the crab does not seem unhappy...
See pic...you have to look at the left tip of his shell....


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New member
No, this is the right forum for this kind of thing. I'm not too sure about what it is, but if I had to take a guess I would say that it is some kind of worm.


Premium Member
Those are the two feeding appendages of a polychaete worm in the family Spionidae, probably genus Polydora. Many of these Polydora species are specialized commensals that live only in shells; some will only live in shells occupied by hermit crabs. They are harmless to the crab. The one negative is that their burrows can weaken the shell if the hermit is attacked by a predator


Premium Member

Good or bad? Well, you've got to remember that I'm extremely prejudiced. Worms are wonderful and corals are only good as substrates or as food for more interesting inverts. :lol: All the same, this type of spionid is not particularly bad or good & will not have any noticeable effect on either the hermit or anything else. If there's only one you won't have a population explosion either.