Small Crab living inside a Candy Cane?

[Big L.E.E.]

Yesterday my wife noticed a small crab (< .5") peeking out of a hole in one of our Candy Cane polyps. The particular polyp seems healthy enough.

I've heard of acro crabs, but a crab living inside a LPS polyp?

 

[charlesr1958]

Its very common to see crabs living amongst any number of coral species, although having a burrow in the corals skeleton is not a good thing since as the crab grows, it will continue to enlarge the burrow as well as probably stealing some of the food the coral manages to capture.

Crab hitch hikers

Chuck

 

[fanaglethebagle]

Thats really cool, I want one!

 

[LeslieH]

What you have might be a coral gall crab. These are pretty interesting little critters in several genera. The females live trapped inside their galls & feed on either particulates in the water or on the mucus produced by the coral. The males are smaller than the females & re free living; they can slip into the females' homes when it's time to mate. One species cultivates algae inside it's burrow. Researchers think the algae helps eat away the coral's skeleton so the crab can enlarge it's burrow. One or a couple of such little guys on your coral won't hurt it a bit.

There aren't many images of gall crabs on the web. Here are a few:
http://decapoda.free.fr/illustration.php?n=1&sp=2056
http://www.dafni.com/crustacea/hapalocarcinidae.htm
http://cookislands.bishopmuseum.org/species.asp?id=7372

 

[magdelan]

I think I may have one living inbetween the polys of my acan. He's really hard to see though but I can see is little claws every now and then.

 

[zenya]

Leslie,
I think you had identified this crab as a true gall crab for me.

I had noticed this crab about a year ago living in my Faviid coral and there is no apparent problem at all.

 

[LeslieH]

Gene - Sure it was me? I don't recall seeing that pic before and it's such a nice one it should be easy to remember. One of my friends is a specialist on gall crabs. I can pass it on to him for an id.

 

[zenya]

<a href=showthread.php?s=&postid=9266368#post9266368 target=_blank>Originally posted</a> by LeslieH
Gene - Sure it was me? I don't recall seeing that pic before and it's such a nice one it should be easy to remember. One of my friends is a specialist on gall crabs. I can pass it on to him for an id.

Leslie,
This shot was in the reef slides in the RK magazine and I believe I saw your identification of this particular crab as a true gall crab, Haplocarcinus marsupialis.
http://reefkeeping.com/issues/2006-04/reefslides/images/zenya.jpg

If I am wrong then I apoligize.

 

[LeslieH]

Oops, I'm the one with the faulty memory - had to go back & search through my old messages to be sure. Doubly faulty as I got the id wrong (must have been a really late night :rolleye1: ). While it's a gall crab it's not Hapalocarcinus marsupialis. If you look at the some of the images in the links above notice that the anterior edge of the carapace is smooth. The edge in your animal is serrated. I will send it off for another opinion so we can get the right name on it.

 

[zenya]

Thank you, Leslie! It would be great to have a true scientific name for that little girl. Your efforts are very much appreciated. :thumbsup: