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FAQs about Marine Crab Identification 7

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 Invertebrate identificationMarine Crabs 1, Marine Crabs 2Marine Crabs 3, Marine Crabs 4, SW Crab ID 5, SW Crab ID 6, SW Crab ID 8, SW Crab ID 9, Marine Crab ID 10, Marine Crab ID 11, Marine Crab ID 12, SW Crab ID 13, SW Crab ID 14, SW Crab ID 15, SW Crab ID 16, SW Crab ID 17, SW Crab ID 18, SW Crab ID 19, SW Crab ID 20, SW Crab ID 21, SW Crab ID 22, & 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,

Cool crab? Neale comes out of his FW shell! 6/10/07 Good morning crew. <Good morning. I'll take a pass at this one with my marine zoology cap on, though I'm sure Bob F or someone else will correct me if I'm wrong...> Any idea what this crab is (see attached). <Not at all clear from that photo. All I could see was an orange blob.> At first, I thought it was an orange sponge but after watching it for a while, I see that it crawls around my live rock and grazes using some type of arms/mandibles. It's tiny--maybe half a cm. I think it came in on some Florida aqua cultured rock that I added. <Given your description and its provenance, I'd suggest some Atlantic species of Schizophrys, sometimes known as "Decorator Crabs". Of questionable value in a reef tank given the fact these animals are fairly omnivorous and can potentially catch and eat small fish, shrimps, etc. They will also chop up things like sponges that they want to use for decoration, as per their common name. Perhaps most fun in a fish-only system with larger tankmates?> <Cheers, Neale>

A "Guest" Arrived on my Live Rock:  Velvet Swimming Crab (Necora puber)   5/13/07 Hi Guys, <Hi Kim, Mich with you.>   I just wanted to start by saying your site has been a tremendous resource!  It has helped me many times. <Wonderful to hear!>   I have tried hard to find an answer to my question without having to ask but I'm not having much luck.  I hope you might be able to help me out. <I will try!>   I purchased 75 lbs. of live rock recently and after about a week I found a "visitor"  I noticed a rather large (aprox. 2 inches) crab hiding in one of the holes in the rock.  After many attempts of trying to identify this crab I finally found out what he is.  It is a velvet swimming crab.   <Necora puber> His bright red eyes were the major give away on his ID.   <Ahh, yes, also called the Devil crab.> I can't seem to find much information on him other than he is very aggressive and gets about 4 inches across.  I was wondering what your opinion is on him.  Should I leave him in the tank or find him another home?   <I would not keep this crab in a tropical marine setup.  It is not a tropical species.  This crab is typically found in the North East Atlantic, off the shore of the UK!  I'm not quite sure how it ended up in your live rock.  This crab can pack a pinch that could bring tears to your eyes, so please be careful.  Perhaps a nearby public aquarium could provide a suitable home.> The tank he is in right now is a 72 bow-front FOWLER set-up.  Thanks for your time. <You're welcome!  Mich> Kim

Re: a "guest" arrived on my live rock (Necora puber)?, update: now Eriphia sebana.  -- 5/13/07 I must apologize, <No worries.> I just got a call from my LFS and they think they may have found out that he is NOT a velvet swimming crab. <Ahh, the initial ID did not make much sense, as Necora puber is a cool water species, but stranger things have happened.> After doing their research they now believe it might be Eriphia sebana. <This would be more logical.> We have been working for over a month to ID this guy.   <Could have sent a photo here.> Which from what little bit of information I can find on him makes more sense being that they are from Fiji.   <Yes, along with Australia, the Maldives...> Could you tell me a bit about Eriphia sebana?   <Will try.  Hmm, it seems I'm on a toxicology run.  What ever you do, don't eat this crab! Ingestion can result in PSP Paralytic Shellfish Poisoning and I suspect this potential for toxicity could also cause problems if the crab were to die in you main system.> Should I leave him in or remove him.   <I would keep him isolated.> I do have an empty 10 gal. with live rock already set up and cycled for a hospital tank....could I keep him in there?   <I think this would be wise.> If so...what should I feed him.   <Most crabs aren't too finicky.  I would offer a variety.  Reportedly this crab eats algae during the day and relies on predation for midnight snacks!> I'd hate to get rid of him, he is very neat to watch at night. <Watch, learn and enjoy!  But be aware he can be an aggressive crab so between the aggression and the toxic potential, you may need to keep this a species tank.>   Thanks again for all your help, <Welcome!  Mich> Kim

Crab Question, ID Likely a Boxer Crab (Lybia tesselata)   5/13/07 <Hi Jason, Mich here.> I have seen a crab in my tank and it looks like it has feather duster tips for arms and he waves them at his mouth like he is eating stuff. <The "feather dusters" you refer to are likely small anemones in a mutually symbiotic relationship with a Boxer or Pom pom crab.> He has small claws too. Do you know what kind it is? It is maybe a quarter inch in size. <Sounds like a Boxer Crab (Lybia tesselata). A picture here:   http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm and more on Google images.  They are generally reef safe, can be fed minced meaty foods and should not be kept with aggressive tankmates.  A delightful little addition!  Do enjoy!>     Thanks for your time. <Welcome!  My pleasure to assist.  Mich> Jason

Mystery Crab ID - 04/22/07 My reef tank has been up and running for about a year and a half now and this morning when I saw the tank there was a huge purple crab on the side of my clam that I have never seen before. <<I see it>> I searched on Google and a few other sites and can't seem to find any info.  If you know what it is and if it's reef safe I would really appreciate it.  Thanks - John <<Well John, this may be a box crab, of which there are about 40 different species I think...and no, I wouldn't consider it to be "reef safe."  EricR>>

Re: Mystery Crab ID - 04/23/07 <Bob, where did you put the ID pc?> Thanks I appreciate it. <<Welcome>> Yeah, I woke up this morning and saw him eating the side of one of my clams!! <<Yikes...time for this crab to go!>> Any advice on catching him? <<Mmm, can be difficult...try sinking a small glass jar in to the substrate or among the rockwork, and place a small piece of meaty food in it (table shrimp does fine).  If you can entice the crab to enter the jar (may need to leave in place overnight...may take several attempts), you "should" be able to reach in and cover the top/remove the jar before the crab can scale the slick glass walls.  Regards, EricR>> R2: Mystery Crab ID - 04/23/07 Thanks a lot, I'll give it a try tonight. -John
<<Good Hunting!  EricR>>

Crab ID (Can't Tell From the Pic) -- 04/02/07 Hi guys, <<Howdy Patsy>> Love your site! <<Always nice to hear...thank you>> I can't seem to find any ID info on the crab I recently discovered living in my LR.  I purchased the LR from Tonga and have had it since May of 2006. The crab is about 3/4 of an inch wide, purple/pink in color with a large white strip on its back.  It doesn't like to come out of the rocks. <<A shy one, eh?>> The left claw is larger, I assume it's male.  I have attached a picture, not very clear, but all I have.  He moves to fast! <<Mmm...can't discern much from the picture I'm afraid>> Is he harmful to other inhabitants in the tank? <<An opportunistic omnivore...a good chance it is harmful in some way, yes>> I.e. Snails, cleaner shrimp, or other hermit crabs? <<Possibly...especially if it gets larger>> Anything you can tell me would be helpful. Patsy <<I am not a fan of crabs in reef systems as I feel they are too predatory and opportunistic in their feeding habits.  I can't say what species this crab is, but trapping/removing it is the only safe option in my opinion...the decision is yours.  Regards, EricR>>

Purple Crab ID - re-sent... 4/11/07 Hi, Patsy here. <Hi Patsy, Lynn here> I found a crab in my LR from Tonga and I am unable to find an ID for it. <Understandable - very difficult indeed.> I have just discovered him and have had my tank for a year. <Not surprising - many are shy, nocturnal, and very good at hiding/camouflage (especially when small!)> It just molted and is purple in color with a large white strip down its back. <Pretty!> It has large front legs. I have a picture but it is blurry and hard to see. <I see those big claws!> The crab lives in the rock and does not like coming out. I see its claw occasionally picking at the algae growing on the rock. I hope you can help. <Unfortunately, crabs are very difficult to ID to specie level but the main issue is that most are not reef safe. They're opportunistic and omnivorous, so although yours may not pose a threat at its current size, it's very likely to do so as it grows larger. My recommendation would be that unless it's alone in your tank (no fish/corals) then I'd remove it, or at the very least, keep an eye on it and its tankmates. Please see these links for more information and good luck! http://www.wetwebmedia.com/swcrabidfaq3.htm http://www.reefkeeping.com/issues/2003-12/rs/index.php > Thanks Patsy <You're very welcome!> PS: Love your site!<Thank you very much indeed! -Lynn>

Emerald Crab ID??   3/11/07 Hey guys, <Brian> I went to a LFS to buy an Emerald Crab about 2 months ago, when I got there they were all tan/beige colour. The LFS said that it was because of the algae they were eating in the tanks. <Mmm, could be, I had a pizza last night and this morning I was yellow.  Do not believe this is the case.> I bought him anyways, my last Emerald Crab was bright green so I figured the new one would turn green eventually. He just molted today and now is gigantic compared to the original size, but still hasn't turned green. Do you think that maybe they pulled the wool over my eyes and that its not an emerald crab? It looks the exact same as my last green one, same carapace, same hairy legs, same claws but he's just beige instead. What do you guys think? <I'm not aware of any beige Emerald Crabs, the name certainly implies the color.  Bob?> <<Not all are green, nor stay green. "Follow the Yellow Brick Road"... B>> Thanks <Brian, in future queries, do cap beginnings of sentences, proper nouns, and "I's".  We just do not have the time to correct text before posting on the dailies.  James (Salty Dog)> Brian

Crabs in my reef?  Yes a Coral Crab (Trapezia ferruginea)  3/10/07 Hello Again Bob, <Hi Brian, Mich here tonight!> I found some crabs hanging out in a couple of my Acropora corals last night. I have pulled them out of the reef, but still have no clue what kind of crab they are. There are 3 photos below if you could tell me what you think they are it would be greatly appreciated. <This looks like a Coral Crab (Trapezia ferruginea).  They are reef safe and eat mucus off their host coral.  They usually hitchhike on stony corals and are typically hardy when provided a host, which is usually a Pocillopora spp. or a Stylophora spp.  If you want them to live, and you should, they need to be returned to their respective corals.> <Welcome!  -Mich>

Crab I.D.  Emerald crab (Mithrax sculptus)  3/9/07 Thanks for a great website, it's a wealth of information! <Thank you for you kind words.  Glad you find it useful!> My question for you is this: This crab came in on my Bubble Coral and I'm just wondering what kind it is? and, is it safe to keep it in my reef tank? <Well you appear to have a inherited an Emerald crab (Mithrax sculptus).  They are generally considered reef safe herbivores in so much as any crab can be truly called this.  But there are a few reports of this species attacking sessile animals.  Is generally OK with an occasional bad egg.  Is one of the few creatures that will eat bubble algae (Valonia).  More here and links in blue:  http://www.wetwebmedia.com/mithraxfaqs.htm Thank you very much, <You're welcome very much!  -Mich>

Can you tell me what crab this is:   2/20/07 Sincerely, Marty Dick <Mmm, nope... other than to agree with you that this is a Decapod, crab. BobF>

Crab ID, please help   2/13/07 Here are two photos of a little hitchhiker crab that I chased around my display tank for the better part of eight months until I caught him and banished him to the sump of my prop tank. :) <Is a beauty!> I talked to a lot of people who ID'ed him (without a photo) as being a gorilla crab because of the bristles on his legs and the black pincers. <Mmm, well is very likely a Xanthid ("Dark fingered crab" family Xanthidae) member...> However, to me, he looks more like a Emerald Crab on steroids. They also have the same bristles on their legs, <Bristles are not a useful identifying characteristic here> and they also have very similar markings on their carapace. A lot of people have said that the black, sharper pincers are a giveaway for a meat eater, but I'm just not so sure. <Is so for the family, yes...> These are photos I took about a month ago when I finally caught it. One guy from my club said it was likely a "Mithraculus forceps" and quoted page 149 of the sprung invertebrates book, <Nah> which of course - I do not own. He claims it this is a brown version of a emerald crab and prefers green algae for food. <Negative... wrong...> I'd like to put him back in my main tank because I need some more scavengers in there, and why pay for something I already own... <Uhh... is decidedly more of an eater upper than cleaner upper> But I don't want to potentially endanger any of my small fish or other livestock based on a bad ID. Please let me know what you think before I let him loose on my hair algae. <Won't be eating much of this> FWIW, if this guy *is* reef and fish safe and is "Mithraculus forceps" I would order more of this species any day over the emerald crabs. They have much more "personality," are much more animated, and seem to be a nice little crab. I will anxiously await your response. JW <Well... if you want to (continue) to feed this "meat eater" in your main system and tolerate some "picking"... this is up to you. I would keep this animal... but likely in a sump, where it would do little harm. Bob Fenner>

Re: Crab ID, please help   2/13/07 > <Well... if you want to (continue) to feed this "meat eater" in your main system and tolerate some "picking"... this is up to you. I would keep this animal... but likely in a sump, where it would do little harm. Bob Fenner> Follow-up question... Could you please define "picking" <Sure... lightly sampling to eating (to death) what it can get hold of> Is he a risk for my other animals?? Might he sneak up on a small goby and have his way with them? <Yes... is possible> I'm not sure I completely understand what risks he might pose. <Such decapods... small to larger... are opportunistic omnivores. Understanzee? BobF>
Re: Crab ID, please help   2/13/07 Thanks for the reply, Bob. Not what I wanted to hear, but that's the way it goes. Thanks again. <Welcome my friend. BobF>
Re: Crab ID, please help [3]   2/13/07 Yep. We is clear. <Ah good> Thanks again for the service you provide. <Welcome> Thanks to your website and your books, you have empowered me to create a sumpless 29 gallon aquarium that looks like this... <Ahh, a pleasure> Unfortunately my wife and I just had a 10 week premature baby that needed a couple surgeries to get things right, so it looks like my volume won't be increasing any time soon. JW <A shame for the young to endure such. Life to you my friend. BobF>
Crab identification 1/19/07 Dear WWM, <Greetings.> First, I'd like to thank you for your awesome database of knowledge about Reefkeeping... <Welcome. You might say, we're here for you...> I found almost anything I was wondering about in your pages... well, except for my little problem: I have this crab (see pic) in my tank since the beginning of it, 7 months ago. It has shown no harm for the moment, he's just hanging out in his cave, sometimes with part of its legs out to fish some food when it's meal time. Whether it's 10am, 10pm, 3am, he's always in his cave, never caught him out wandering... When he's half out of cave, if a fish comes by, he immediately rush into his home. He's hairy, light tan skin with dark red irregular spots/stains, neon green eyes, darker brown tipped pointy claws, maybe an inch large for its back (not with the legs). Actually, my problem is everybody is telling me to kill him, but I first I never killed an animal and I'm very reluctant to do so, and then I don't want to kill an animal just because he might be a predator, but with no certainty. <It' up to you what you do with your aquarium, but the rule of thumb I used to use with crabs when I was in retail was: "If it's hairy, it's not beneficial". We also have a saying here at WWM, "When in doubt, take it out". Now, that doesn't mean it can't be a good pet, but it may end up predating a prize fisherino sooner or later.> So I'd like to know FOR SURE whether he might be a threat to my fishes (and I'll be forced to kill him, because I have no sump nor refugium), or if he'll still be small and shy all his life long (and I'll consider him as a friendly part of the population). Can you tell me the exact species, and how tall he'll be as an adult? <Let's give a look...mmm, no I don't have a Latin name for you here, but I will forward to BobF for possible positive ID. I was thinking about a Pumilus crab, I saw a photo once, it looked quite similar, but couldn't find any info on the net about this specie... <Ditto...> kind regards, and best success for 2007! <I would check the crab ID FAQs here on WWM ( http://www.wetwebmedia.com/swcrabidfaqs.htm ) Thanks for the -Graham T.

Red hairy crab sorry sent with out picks   1/12/06 HI, <Hello there> First I just want to say thanks for all of the help! <Welcome> I am coming up on one year with my first saltwater tank and you guys have saved it many times. <We have helped you save it> I have a 95 gallon with about 85lbs of live rock and many fish and corals. I have a red crab that has hitchhiked into the tank on LR.  I think he may have been nibbling on my Yellow Fiji Leather but I am not sure.  He was hiding under it for a while and it was not opening all the way.  Otherwise I have only seen him eating off of the LR.  Are you familiar with this red crab, is he reef safe, and should I keep him or get rid of him? <Nice images... I don't know what this crab is... but I would keep it isolated from your main reef livestock...> See attached pictures.  I was able to catch him after about a month of trying so that I could quarantine and take pictures.  I do not want to kill him if it is not necessary.  However I have grown a very diverse environment of small organisms and do not want them wiped out nor do I want anything eating on my corals. <I understand> Thank you, for any assistance that you can provide. Bryan E Stone
<Perhaps in a sump... Bob Fenner>

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