Unknown purple crab!

azrien · #1 07/11/2006, 11:14 PM

Tonight, I shined a flashlight into the tank and inspected the rockwork, looking at worms and creatures, and in one crevice I found this huge purple crab! It's at least an inch and a half wide and purple as ever. These are the best photos I can get. Any ideas? I tried a Google image search however there are lots of purple crabs that don't quite match. A friend of mine is guessing a type of porcelain crab. *Edit* It seems to have quite large claws in relation to its body size, it has white filters (does seem to be a filter feeder), and it is a purplish maroon with white dots.

I realize the photos are terrible, however I have never seen this guy before and I might not again. Any attempts at an ID are greatly appreciated, especially a theory on if it's reef safe or not, but I'm not going to tear down the tank trying to get a better photo. Hope this will suffice!

The better photo:

The worst photo, but shows more general shape:

If I happen to get anything better I will post here. Thanks!

LeslieH · #2 07/11/2006, 11:39 PM

It looks much more like a xanthid to me but it's hard to tell just from the pics. Take a look at the links below. The first goes to 3 pages of xanthid images (still only a fraction of what lives in a reef), the second has close ups of various porcellain crabs, and the third has some excellent images (click for enlargements) of the filter feeding structures typical of porcellain crabs. Maybe they'll help you decide.

http://www.flmnh.ufl.edu/reefs/guam/...dae/index.html
http://www.nhm.org/guana/bvi-invt/bvi-surv/anom-g02.htm
http://www.daveharasti.com/articles/...celaincrab.htm

azrien · #3 07/12/2006, 11:41 AM

Out of all of them I would have to say it's a Xanthid. It looks very close to this guy here: http://www.flmnh.ufl.edu/reefs/guam/...es/Image1.html

The only problem is that the coloring is a bit different. Also, I have to see if it's a filter feeder because this guy definitely was filtering, although his filters weren't nearly as long as a porcelain's. I'll have to wait and see, though! I will assume reef-safe though, just because I think he was in the tank for a very long time with nothing eaten.

Thank you for the links!

nUgZ · #4 07/12/2006, 02:46 PM

I was just about to start a thread for the ID of my crab, but it seems to be the same as this one. I have some better shots so maybe they will help. My crab is actually about 2 1/2 inches wide. Here are the shots.

Hope this helps.

P.S. I got this crab from a guy who had been trying to catch him for 3 months. He said he ate a majority of his tank inhabitants. I would say not reef safe.

azrien · #5 07/12/2006, 04:32 PM

We've got the same guy! Yeah, after further reading I have determined it to be unsafe for the reef, and as I am devoid of a 'fuge I'm going to have to explore other options. My bro in law has a humuhumu that's always looking for good things to eat. It's a shame too because he looks awesome and hasn't tried to eat anything *yet*.

On the plus side, I am very happy my clownfish stays north of the rockwork and sleeps "laying down" at the water surface. The farther away he stays from the crab, the better.

Where/how do you keep yours? Would you like another?

nUgZ · #6 07/12/2006, 05:24 PM

I really wouldn't mind another. I've got mine in his own 10 gallon that I'm getting ready for a Mantis Shrimp. I was inspired by the tales of Tim the Supermantis. He hasn't eaten any of the hermit crabs, snails, fish or Zoanthids in there with him. I've only had him about a week but he seems ok. I can say that he is VERY strong...lifted a rock that weighs 2-3 lbs.

scubamike · #7 07/12/2006, 08:32 PM

awsome looking crab, I saw one in my sump the other night but he was hiding. didnt get a good view but maybe the same

DensityMan · #8 07/13/2006, 12:04 PM

I can hear Tim smacking his lips from my office at work...

Lev F. · #9 07/13/2006, 01:30 PM

Looks like a Red-Eye Crab. I used to have one in my reef as a hitchhiker, but he ate my corals, so it's the refugium for him.

LeslieH · #10 07/13/2006, 02:00 PM

They sure do seem to be the same. This particular crab is fairly common in live rock from the Indo-Pacific judging the frequency of posts that ask about it. He may look like a filter feeder to you but I bet he's a typical xanthid and feeds on whatever it can get.

Krazy · #11 07/13/2006, 02:47 PM

Yeah, I've got the same guy in a container floating at the top of my tank ... I'm gonna have to bring him to the LFS or a local member of my club...

azrien · #12 07/13/2006, 02:58 PM

I've decided to keep him for now and watch him carefully, perhaps direct more food to his location, and move him to the sump/fuge when we get that going. We're moving within a month and during that move the tank (or a new one) will be drilled and set up to have a sump/fuge. When that happens, this guy is going to have a home in there. He doesn't seem to go anywhere except on the "porch" of his cave. Just as well, too.

I'm sure he'll be useful in a fuge and if he's come this far without touching anything, another month shouldn't make a difference. Of course now that I've said that, he's going to mow the coral lawn, so to speak..

azrien · #13 07/13/2006, 03:52 PM

Actually, what corals do these xanthids eat? I had a couple mushrooms in my tank for awhile and one day I noticed my large one was gone. My smaller one got sucked into a powerhead intake sometime later and I was able to pull it out and rescue it, but I never saw the large one again. I assume it got sucked up. Now I wonder if the crab came out and had dinner. Can anyone confirm if they make meals out of mushrooms?