Related Articles: Crabs, Hermit Crabs, 

Related FAQs: SW Crab Identification 1, SW Crab ID 2, SW Crab ID 3, SW Crab ID 4, SW Crab ID 6, Marine Crab ID 7, Marine Crab ID 8, Marine Crab ID 10, Marine Crab ID 11, Marine Crab ID 12, & Marine Invertebrate identification, Marine Crabs 1, Marine Crabs 2, Marine Crabs 3, Marine Crabs 4, SW Crab ID 5, SW Crab ID 6, SW Crab ID 7, SW Crab ID 8, & Crab Behavior, Marine Crab Selection, Marine Crab Compatibility, Marine Crab Systems, Marine Crab Feeding, Marine Crab Reproduction, Marine Crab Disease, Micro-Crustaceans, Amphipods, Copepods, Mysids, Hermit Crabs, Shrimps, Cleaner Shrimps, Banded Coral Shrimp, Mantis Shrimp, Anemone Eating Shrimp, Crustacean Identification, Crustacean Selection, Crustacean Behavior, Crustacean Compatibility, Crustacean Systems, Crustacean Feeding, Crustacean Disease, Crustacean Reproduction,

Hitchhiker Available For Food 1/14/08
Hey there.
<Howdy>
Enjoy the pics of this guy I caught over the weekend! With those red eyes, probably nocturnal, coming out to creep when lights out? I think
it must be over 3 years old, since that's the last time I added any live rock. He's currently being fed & held in a container in the tank. Hoping
someone local may need some puffer or mantis food or want it for a sump.
CRAB PIC 1 <http://stonyreef.com/blog/wp-content/uploads/2008/01/crab.png>
CRAB PIC 2 <http://stonyreef.com/blog/wp-content/uploads/2008/01/crab2.png>
<Gee thanks for trying to share with us, but a copy/paste of the links leads me to
error pages. Best to attach photos to the email. James (Salty Dog)

Hitchhiker Available For Food 1/15/08
Attached :)
<Got them now, thanks for sharing.>
Thanks!
<You're welcome. James (Salty Dog)>

Can you help ID this crab? Mithraculus? 1/13/08
<Hi there>
Found this hitchhiker in a piece of live rock. Took me quite a bit of time to coax him out with some food. Is this crab reef safe?
<Depends on what you have in your tank, but crabs in general are not a good idea in a mixed reef tank. They’re mostly opportunistic omnivores, and “pickers”, that may start out small and cute, but can become a problem later on (nabbing fish/other inverts, picking on desirables, etc).>
What kind is it?
<Not sure - would need to know where it was from, as well as a shot from above showing all legs/shape of the carapace, as well as one showing the claws. Judging by what I can see in the photo though - hairy walking legs and what appears to be the potential for blunt/clubbed claw tips - it looks somewhat like a Mithrax/Mithraculus sp. This is the same genus as the commonly offered “Emerald Crab” (Mithraculus sculptus) that some use for algae control. Most have more pointed "faces", but some do not. Next time you see him out and about, take a close look at the tips of his claws. If they’re blunt/spatulate instead of sharp/pointed, then it likely is a Mithrax. However, it also looks like it could be a Pilumnus species (Family Xanthidae), although it’s hard to tell in the photo if the carapace/claws are hairy, and if so, to what degree? Xanthids are, unfortunately, some of the more destructive candidates for reef tanks. For more information, please see these links (as well as related links listed above at the WWM link):
http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm
http://www.reefkeeping.com/issues/2003-12/rs/index.php>
How big will/can it get?
<Can’t be sure without knowing which species we’re dealing with.>
Any input is much appreciated.
<You’re very welcome. Keeping a crab in a reef tank is a risk, but if you decide you’d like to let him stay, keep an eye out for damage and trap/remove if/when necessary. Take care. -Lynn>

Mystery crab hitch-hiker -12/22/2007
Hello gang.
Thanks for such an incredibly comprehensive site! Thanks to you, I've given up searching the rest of the web most of the time anymore.
<Haha... thanks.>
On to the question: I'm looking for an ID on this crab, if possible. He showed up magically in my refugium-to-be a couple days ago. The refugium was set up about 2 weeks ago in preparation for an order I had coming from Floridapets.com. Although the tank itself hasn't been up and running for all that long, nearly all of it's contents came from a 10 gallon and a 5 gallon tank that had been going for about 3 months previously. It's a 29 gallon with deep sand bed, powerhead, whisper internal filter (rated for a 10 gallon, but mostly just used for circulation), and a cheapo style Berlin skimmer (air stone type). My plan is to let all the recent arrivals be in that tank for a month or two before I hook it up to my 20 gallon nano reef as a refugium. I'm monitoring the water quality closely, especially since this tank is so recent to be having livestock in it. I keep the ammonia & Nitrites at 0, and don't let the nitrates get over 10 or 12 mg/L. Usually less.
<Sounds like things are going/cycling well/as expected.>
Anyway, back to the crab - I got a ball Chaetomorpha, and 2 pounds of live mineral mud from florida pets, and he must have hitched along with that somewhere. He's about the size of a dime, including his legs, and he moves sideways. He holds himself kind of like a boxing crab, but he obviously doesn't have the coloring of one. He seems to prefer to dig himself a pit under a rock or shell, that he can back into and hide, and he's about the color of the sand, so he's pretty well camouflaged. I've seen him sorting through the sand, I assume looking for food. Also, a friend gave me some Hikari "crab cuisine" she had for her turtle, and this little guy eats those with great relish.
<Hmmm... crabs are notoriously difficult to ID (especially from photos). It looks like some kind of Mithrax or Xanthiidae crab to me.>
Of note, maybe, is that he only has a claw on the left side (hopefully the photos show it kind of clearly). I don't know if that's because he's a lefty by genetics, or by chance. I haven't had him long enough for a molt, so it's hard to say for sure.
<It's most likely he lost the right claw in a fight or in the journey/shipment from wherever he/she is from. It should grow back with time.>
His tankmates include: 1 coral banded shrimp, about 15 hermit crabs (dwarf yellow tipped, and red-legged), a tiny frag of a yellow gorgonian, Nassarius snails, keyhole limpets, a small Aiptasia anemone (keeping a close eye on that one), and a feather duster worm.
I'd like to know what this crab is, so I can keep him alive, happy, and out of trouble (and everyone else safe, if appropriate).
<Unfortunately, I can't honestly tell you much for sure. But given his/her overall appearance and your noted observations, my GUESS is that he's your typical scavenger/picker. If you want to keep him, I'd just keep feeding him what you're feeding him. Sometimes even the "bad" crabs can be kept more or less "well behaved" if they're a relatively smaller species and if you keep them well fed so that they don't have to start getting aggressive/adventurous for food.>
Thanks very much in advance,
-Heidi
<De nada,
Sara M.>

Mystery Crab ID: Huenia spp. – 12/20/07
Hey Crew! *waves*
<Hi Christopher! *waves back*>
I wrote to you about a week or two ago, but unfortunately never received a response or was able to find one on your site.
<Oh, I’m so sorry!>
So I'll try again :)
<We'll try again!>
First off, you'll be happy to know that I removed the porcupine, dog face, and clown trigger from my 55 gallon tank and brought them back to the LFS.
<Yay!>
Now have 2 Perc clowns, 1 yellow tang, and 4 Chromis. Whewph glad someone pointed that out for me about overstocking! My LFS seems to be more interested in $$$$ than :) Everyone in the tank seems really happy now, thanks :)
<Great to hear.>
Now to get back to my question, the one I couldn't find a response for. I found a crab who was a hitchhiker in my tank and am super curious what he is!
<He's a neat little crab, that's what!>
He's lime green, quite small, and seems to have what looks like a plant for a head.
<Heee, like in that commercial where people have flowers growing out of their head?>
I'm attaching a picture. If you can provide any info or a link to read on what he is it would be much appreciated. I cannot find anything! (Try typing in crab with plant for head, it doesn't work well) hehe.
<LOL I bet that was interesting! What you have is an algal commensal called Huenia heraldica, commonly called an arrowhead, Caulerpa, or Halimeda crab. Please see these links for more information/photo comparison:
http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm
About two thirds of the way down the page at this next link - and would you look at that...one appears to have Halimeda growing out of its head! It’s a Halimeda hat!
http://www.starfish.ch/collection/spidercrabs.html >
Thanks again!
<You're most welcome!>
#1 Fan Christopher
<Woohoo! Thanks! -Lynn>

Re: Mystery Crab ID: Huenia spp. – 12/20/07
<Hi Christopher!>
Wow you're good! I'm impressed! Thanks sooooooo much!
<Well, we can both thank Bob for that one! I knew I’d seen that little guy before, and sure enough I had – at WWM!>
Have a great day and hope the holidays go well for you and yours :)
And Merry Christmas if that's ok to say :)
<It's absolutely ok to say, and I thank you very much! A very Merry Christmas and a Happy New Year to you and yours as well :-)>
Christopher
<Lynn>

 Re: Help ID'ing a crab - 12/11/07
<Hi Michael!>
Thank you for taking the time to answer my question.
<My pleasure.>
The sites you pointed me towards were a great help and narrowed it down quite a bit.
<Excellent!>
I wish I could provide more pictures, but he's very skittish and seldom comes out of his hole. I actually had to entice him out with a piece of squid.
<That’s good to know when/if you need to trap him!>
Anyway, here's a few more details about him. He has a trapezoidal shaped body, which makes me think it's possibly a type of Grapsid crab?
<Quite possibly, yes.>
The colour is a very light grey almost white with small hairs. He also has faint vertical maroon brown stripes on his body and legs.
<Pretty little crab :-) I wish I could be more specific with an Id, but considering the number of species out there, I think you’re doing well to narrow it down to a Grapsid. What’s important is that most crabs are not to be trusted long term in a reef tank, so I'd either keep a very sharp eye on him/his tankmates, or trap and relocate.>
Once again, thanks for the knowledgeable insight!!
<You’re most welcome!>
You guys rock!!
<Woo-hoo! Thanks, Michael!>
Michael
<Take care -Lynn>