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FAQs about Marine Crab Identification 8

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, SW Crab ID 5, SW Crab ID 6, SW Crab ID 7, SW Crab ID 9, Marine Crab ID 10, Marine Crab ID 11, Marine Crab ID 12, SW Crab ID 13, 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, Marine Invertebrate identificationMarine Crabs 1, Marine Crabs 2Marine Crabs 3, Marine Crabs 4, 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,

Please help identify this crab: Ocypodid - 11/30/07 Hello, <Hi there.> can you please help identify this crab for us. <Will sure try!> We got this crab from our LFS and have researched it on your site, but could not find any information about this crab. In one of the pictures you can see that he raises his eyes. <Yes, I see.> Any information would be great. <Unfortunately, I can't Id it to species level, but I can narrow it down a bit. I believe what you have is likely an Ocypodid (family Ocypodidae). This family includes intertidal/shore crabs, commonly called fiddler crabs, and ghost crabs. The first clue is that set of extraordinary eyes. Crabs with long eyestalks like that are generally intertidal/shore crabs. Although there are many families that contain such crabs, yours seems to fit Ocypodidae best. There are several genera under this family, and more subgenera, so identifying it further gets a little tricky. I tend to think that it's in the genus Uca (fiddler crabs), as opposed to Ocypode, mainly because of the slender eyestalks - but I could be off. Your crab doesn't have the characteristic oversized chelae/claw typical of a fiddler, but it could be a female or just too young to have developed one. Again, this is all speculation. I'm sorry I can't be more specific! Please see this link for basic morphology/comparison re: http://www.fiddlercrab.info/uca_morphology.html You're probably wondering at this point, just how suitable this crab is for your tank. Unfortunately, not knowing your situation, I can only speculate. Shore/intertidal crabs spend time above/below water. Some come out at night, or when the tide's out. Some live on the beach/mudflats in burrows. If in fact, you have a reef tank, I can't imagine a crab such as this doing too well long term, but I could be wrong. One last thing of note is that crabs, in general, tend to be opportunistic and may decide to prey on/pick at any number of organisms in your tank, so unless this is a species-specific system, be sure to keep an eye out for any resulting damage/loss. One thing's for sure - it's a very pretty little crab!> Thank you
<You're very welcome -Lynn>

Crab ID please... Atergatopsis signatus, the Giant Egg crab   9/28/07 Hi Guys... <Hi Jo, Mich here. Sorry for the delay.> This crab hitched in on some live rock a few months back... <Is a very pretty crab!> I've been back and forth all over and I can't seem to get an ID on him...His nippers aren't overly large, and he doesn't seem to be doing any damage to corals or fish, <I hope this continues to be the case, but crabs are never to be trusted.> I'm just curious what he is so I know how big he will get...he started out at around 1cm across his back and now, 6mths later he's around 3cm across his back... <Well, if my ID is correct, Atergatopsis signatus, the Giant Egg crab, can reach up to 12 cm across! That's pretty big for any aquarium. You may need to consider a different home for this beauty. Do you have a nearby public aquarium?> he is the most beautiful shade of lilac and very smooth...he spends most of his time in a deep hole in the live rock and comes out for a feed at night when I'm feeding the tank...any ideas ??... <I do believe your crab may be a Giant Egg crab (Atergatopsis signatus) but is hard to tell with just one picture. You can see more images here. Particularly look at image # 4:: http://images.google.com/imgres?imgurl=http://decapoda.free.fr/images/brachyura/Atergatopsis_signata~_TAH_928-21.jpg&imgrefurl=http://decapoda.free.fr/illustration.php%3Fn%3D5%26sp%3D85&h=559&w=752&sz=83&hl=en&start=1&um=1&tbnid=28vhb-XTRuaakM:&tbnh=105&tbnw=141&prev=/images%3Fq%3DAtergatopsis%2Bsignatus%26svnum%3D10%26um%3D1%26hl%3Den%26safe%3Doff%26client%3Dsafari%26rls%3Den%26sa%3DG > Cheers...
<And to you! Mich>

Crab ID  8/9/07 Found this small (9.4mm wide carapace) crab under the seaweed on Bailey Island, ME. Don't recall seeing any with a red "V" before. Can you ID please? David Reed <Looks like an unusually coloured European shore crab, Carcinus maenas, to me. The 5-points on the either side of the shell are indicative of that species, though not unique to it. What is more telling is the pointed final segment on the back pair of legs; on most of the similar crabs, these are paddles: shore crabs are more fully adapted to terrestrial life than most other intertidal crabs. The other "walking" crabs like Hemigrapsus have fewer than five points on each side of the shell. Despite its name, the European shore crab has been transported all around the world, including both coasts of the US, so finding one in Maine isn't unusual. They're fascinating animals -- their species name, "maenas", means "mad one", a reference to their amazing fierceness and territoriality. They are very easy to keep in marine or brackish water aquaria, though predatory. They can survive exposure to dry air for days, and will tolerate salinities down to almost (but not quite) freshwater. Anyway, I could be wrong on the ID, so perhaps Bob or someone else will chime in. Cheers, Neale.>

Re: Crab ID  8/9/07 Thanks for the quick reply! David <Thanks for the thanks, but we don't actually know if I'm right! Cheers, Neale>

Crabs... and Ascidian, IDs  -- 08/02/07 Hey Crew. <Hey now! Mich here.> It's been a long time since I last wrote (about 3 days). <Heehee! That is a long time from this email address!> I have some crabs in my display about which I'm curious. Pics are attached. The first pic is just a cool, very big sea squirt that I have--just a cool pic, no question. <Neat!> The second pic is of a decorator crab (I think Schizophrys dama). <Likely so.> It is small (maybe 1/4" tall) and I think it's a really cool crab (watching him lumber about, etc.), but I also know your general feeling about crabs. As you can see, he has poached some polyps from my tree corals. I saw him molesting them tonight, although they didn't seem to mind too much. <Hopefully he's just fragging it and not noshing on it.> Anyway, question #1 is whether I should get him out of the display and, if so, <He's not "reef safe". whether I can put him in my 30g refugium (4-6" DSB with 4lbs live rock and Chaeto)? <Could.> Will it eat my pods/Chaeto? <I'm not sure. I'm not finding much on the diet of this particular species but most crabs are opportunistic omnivores.> I could put him in my 30g QT, but not much in there for him to do. <This may be a good option.> Third pic is of some type of filter feeding crab that I noticed tonight. Not a very good picture, but it definitely has sweeper arms that it uses to filter feed and you can clearly see its filters in the attached pic. It doesn't look like any Porcelain Crab I've ever seen (which is the only crab I found while researching that has similar feather-like appendages). So, question #2 is any idea what type of crab this is? <Is likely a Neopetrolisthes or Petrolisthes species.> Final question (no pic) is the suitability of what I think is a Mithrax forceps (Red-Ridged Clinging Crab). It came in on some live rock and I've been observing it for several months. It doesn't seem to molest anything other than the little bit of macroalgae that I had (notice past tense) in my display. <"Seem to molest" is likely an accurate description... Most crabs are opportunistic omnivores.> Muchas <De Nada!>


Stone Crabs! - 7/18/07 <Hi Bridget!> I have pulled 3 of these guys out of my tank in the past 6 months. <Yikes!> Pet store ID'd the last one and advised an elimination program. All research on the web tells how tasty they are. <I've never had them, but I've heard that as well.> That really is kinda useless. <Well, if you do indeed have the same variety of "stone crab" that they use in the seafood industry, you can try Googling its scientific name: Menippe mercenaria. That's the problem with common names, though. One name can be used for many species.> My biggest question is, are they really all that bad? <Well, not if you want a crab tank! If you want a reef tank with snails, etc, in it, then yep, I'm sorry but they're bad. Crabs in the Menippe genus are Xanthid, or mud, crabs and have a bad reputation for being destructive in reef tanks. Also, some Xanthids are toxic, so just in case, don't let anyone eat those crabs!> If so what's your best advise for removal? <Please see this link and the post labeled 'Trapping in Displays': http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabfaqs2.htm > I do know I no longer have any hermit crabs and my yellow tang has gone missing? <Hmmmm, not good.> Now have 3 fish in the 75, 2 true Perculas and one coral beauty. Thank you for your time Bridget <You're very welcome, and good luck! -Lynn>
Re: Stone Crabs! Follow-up 7/19/07
<Hi again, Bridget! Lynn here.> Well I found some pictures here http://www.okeefes.org/Crabs/crab%20photos%20and%20scans.htm and this guy <(Pilumnus sayi)> is definitely what I have and not the stone crabs <(Menippe mercenaria)> *Pilumnus sayi* <Thanks! Pilumnus sayi, sometimes called the hairy mud crab, or spineback hairy crab, has those same robust claws as the yummy stone crabs (Menippe mercenaria) but with lots of bristles! Unfortunately, it's still a Xanthid and potential trouble down the road for a mixed reef tank.> Hubby is being a grump and not wanting to remove these guys. <I can understand that. As much trouble as they can cause for the other inhabitants of your tank, they're still neat little creatures! Why not set up a separate tank for them? It's a win-win!> Myself, I'm more than concerned about the quantity and I'm wondering if they might be reproducing or if they just came in with the live rock. <Almost guaranteed that they came in with the rock. The juvenile stages of crabs have a next to nil chance of surviving in the average tank.> I don't see these guys. They're professional hiders, <Yes indeed!> I'm only finding dead bodies. <Of snails, etc, or the crabs themselves? If it's snails, etc, that's not too surprising. If it's crab bodies, they could just be the shed shells from when they molt.> Which makes me more concerned about anyone else in the tank. <Understandable either way!> Tank is a 75 reef established 3 years, new live rock with oysters 6 months ago. <Sounds like a nice tank to me!> Thank you for your time. Bridget <You're most welcome, Bridget. I'd try to trap these guys (see previous link on this) and set them up in a tank of their own. Good luck! -Lynn >  

CRAB ID... Yum!   7/16/07 Good Morning, <And to you! Mich here.> This is my first question for the Crew; however you forum has saved me hundreds of dollars and too numerous hours with the information posted on you website. <Very good to hear!> I am trying to ID a crab in my tank. He was in a deep hole in a piece of LR and he only came out at night. He finally got too big for the hole and I managed to get he cornered in another piece of LR. anyway can you help ID this little critter. <Mmm, boy I'm not really sure I can even get this crab to the family level, my guess would be this might be Family Cancridae and it does resemble the Red Rock crab (Cancer antennarius) picture posted on the site... Same family as the Dungeness Crabs. But is more of a guess than an ID. http://www.wetwebmedia.com/marine/inverts/arthropoda/crabs/swcrabs.htm I would doubt that it is reef safe or fish friendly by the size of the claws. Look more like the type you might eat than keep as a pet. I would certainly house him out of the display. Perhaps the refugium or maybe your local Red Lobster would be a more suitable home?> Paul <I suppose it would be just outright wrong to ask if you had any drawn butter? Heehee! Mich>

Crab ID and Clown/Anemone Question -- 07/03/07 Crew, Sorry to lump two different subjects in the same e-mail, but thought it would save you some time. I purchased 65lbs or live rock (50 lbs Fiji/Marshall and 15lbs Florida) about 5 months ago. In the last week or so, I noticed two crabs that hitchhiked in. My face is pressed against the glass every night, so I'm really surprised I haven't seen these crabs until recently (although my tank is 110g). I have attached pictures. I'm pretty sure the first picture is of a sponge crab, genus Schizophrys. It is pretty small and is covered with pieces of orange sponge. The second two pictures are of the same crab. It's hard to get a good shot of it, but it is pretty small (maybe 1/2") and relatively flat with hairy legs. It's claws are pretty small. I've searched the web and WWM but can't find a picture that looks like either of these crabs. My closest guess on the second is the Schizophrys aspera. <Appears to be...> Should I remove these? <Mmm, not yet> Currently, I don't have much in the way of fishes or inverts. One gold banded maroon clown, one BTA, two cleaner shrimp, a pretty good sized clean-up crew, and a Sailfin tang in QT. I intend to stick with smallish fish (but not tiny) and some soft corals. When I bought my clown, he was loving life in a BTA. Since I've had him, though, he's spent much of his life in a hospital tank while my display went fallow for 4+ weeks. I recently introduced him back into the tank and he shows no interest in my BTA. <Takes time...> My BTA is tucked under a rock at the bottom of the tank, but definitely visible, flowing, calling out to his friend, but the clown seems totally uninterested. I find this strange since he was in a BTA when I purchased him. I would love for them to have a hot, lovely relations. Do clowns find anemones by scent, sight, some combination of the two, or none of the two? <Good question... I don't know... perhaps a bit of both... It is known that the fish DO communicate with the Anemones chemically> Are clowns fickle, or can it take weeks or longer for the clown to settle in and accept a BTA? <I suspect both... plus a bit autistic... have short memories...> As always, your thoughts are appreciated. Andy
<Welcome. Bob Fenner>

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