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FAQs about Emerald Green, Mithrax/Mithraculus Crabs: Behavior

Related Articles: Mithrax Crabs, Arrow Crabs, Crabs

FAQs on: Emerald Green Crabs 1, Emerald Green Crabs 2,
FAQs on: Mithrax ID, Mithrax Compatibility, Mithrax Stocking/Selection, Mithrax Systems, Mithrax Feeding, Mithrax Disease, Mithrax Reproduction,

Related FAQs: Marine Crabs 1, Marine Crabs 2Marine Crabs 3, Marine Crabs 4, Marine Crab Identification, 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,


Unusual Aiptasia Predator (Mithrax sp.)? -- 06/18/11
Hi crew,
I don't really have a question today, more of an observation.
<<Alrighty then>>
I have a 55 gallon reef tank and recently noticed a couple small Aiptasia pop up on a piece of live rock.
<<'¦and then they were many'¦>>
I was keeping an eye on them until I could pick up some Joe's Juice.
<<Prefer Red Sea's Aiptasia-X, myself>>
Well my Mithrax crab decided that he had a taste for Aiptasia and subsequently cleaned up my problem before it became one.
Well I guess I have one question, is this an isolated occurrence or have any of you heard of this type of predation?
<<Haven't heard this before, but that doesn't mean it's an isolated occurrence either. This is just another example of the opportunistic and predatory nature of most all crabs'¦do keep an eye on this guy as it gets bigger, else your fishes/other desirable organisms can become its next 'opportunity'>>
Thank you for all the help you, WWM, have given me.
<<The pleasure is ours>>
I wouldn't be enjoying my tank as much without it. You all are the best!
<<We are happy to share'¦Cheers! EricR>>

Mithrax sculptus & Stichodactyla haddoni/Emerald Crab Behavior 3/28/2011
Good on you for making yourselves available to myself and others.
<Thank you.>
I have a Mithrax sculptus (Emerald crab) that uses a Stichodactyla haddoni (carpet, saddle anemone) as cover. The crab walks along the rocks and squeezes itself under the anemone, part of which is spread out and in contact with said rocks. It will move around between the rocks and anemone, and also rest there. I've yet to witness the anemone react to the crab. Will the crab irritate or damage the anemone this way?
<Should not, and is not unusual to see this.><<RMF is not so sure>>
Thank you.
<You're welcome. James (Salty Dog)>

Sebae Anemone And Emerald Crab 1/11/10
<Hello Brian>
I have a had a Sebae anemone for several weeks now. He found a nice place in the tank, and seems to have some good days and some bad days - hopefully he is on his way to adjusting and thriving in my tank, but right now it <I> think it could go either way.
Anyways - I just got 2 Emerald Crabs. 1 found a nice place in a live rock "cave", but the other one has taken an instant liking to hiding under the Anemone. He actually moves the anemone around a bit and almost wears it like a hat - the Anemone is actually more opened up now, and looking a healthier. Could this be a symbiotic relationship, or is the crab hurting the anemone?
<No symbiosis here, the crab is just looking for cover. I suggest relocating the crab to a different area of the tank as to give the anemone a chance to anchor in. You may want to read/learn here as this is not one of the easier anemones to keep.
Thanks for any light you can shed on this strange relationship.
<You're welcome. James (Salty Dog)>

Emerald Crab Turned Decorator  - 05/19/2006 Hello!   I hope you don't mind me emailing you but you seem to know a lot about Emerald Crabs, and their like. So I was hoping you might have seen this before, or can start me down a path to finding out the answer. I have an Emerald Crab that has what appear to be sponges growing on it. Small white sponges, I can see their little hole.  It is on the main body as well as the legs.   I have been looking around for information on it, but this is the only site that I have seen that has any information on crab diseases.  The crab is not dead, or seems to be dying, but I am curious about it, and if it might be detrimental to it in the future. <Would not worry too much about whatever these are.  Once the crab molts, the critters will go with the molt.> Thank you so much for your time. <You're welcome.  James (Salty Dog)> James

Condy and emerald?..... Nemo and Dory? Hi WWM. I have a question for you guys. Is there a connection between Condy anemones and emerald crabs? <Evidently so: http://www.tmbl.gu.se/pdf/TMBL_pdf/Library_and_databases_pdf/examensarbeten_pdf/Lisbeth20p.pdf  > I introduced my Condy (since it was in a in-tank refugium) into the main part of my 55 reef and the emerald crab shot right to it. Always staying right by it like a clownfish with anemone. Perhaps it needs comfort? No predators in my tank. I don't know if you guys have heard of this relationship but it kinda seemed weird to me. This is not the first time this has happened to me. Different emeralds and different Condys. What are your thoughts? Keep up the good work. Teddy <Will try, am trying. Bob Fenner> 

Emerald Crab >I noticed a few weeks ago (~5) that my emerald crab's pinchers were missing. It seems to have lost them during one of its molts. My Sally lightfoot  crab didn't lose it and it molts about 2-3 times a month.   >>You have a mix of two different crabs, both known to become aggressive, are you certain they were lost *because* of the molt?  It could very well be that the Sally Lightfoot (btw, there are at least two, if not three, other species of crab called "Sally Lightfoot"--ALL aggressive) managed to catch the emerald at its most vulnerable.  With such a mix this must be expected. >It is still eating. It has learned to use it legs to get food. Will my emerald crab's pinchers ever grow back? >>Yes. >All the water parameters are zero and I add iodine to help with molting. >>All parameters, even pH, temperature?  ;) >Also what would a likely cause be for the disappearance of my peppermint shrimps? I had 3 but they slowly disappear. >>Quite easily one of these crabs, or you could even have an unknown (and most unwelcome) guest in the form of a mantis shrimp.  If you ever hear odd clicking noises from the tank (especially at night), you may have a mantis.  These animals can decimate a tank. >I have 4 mid-sized pieces of live rock, 2 pink skunk clowns, 1 humbug damsel, and 1 Nemo. Any info would be greatly appreciated. >>There you have it, you have an aggressive (far too aggressive for peppermints) mix of inverts going on there, in my honest opinion.  Marina Thanks

Not a minute-man! (Emerald Crab) Hello, oh helpful ones: <Whassup, bubba?> So the other day, I see my Emerald Crab isn't moving. I figure, okay, I'll wait a day and see if he moves.  Nothing.  So, I finally take the poor guy out and say goodbye.   <literally or figuratively on the "goodbye" part?> Then, I figure, while I have the gloves on, I'll move some of my LR around a little.  Lo, and behold, my Crab moves from under a rock.  A few questions, numerically, if I may: <rock on my brother...> 1.  I guess he molted (this is a first for me)? <indeed... a molt of the exoskeleton. Conspicuous in some lazy arthropods that leave it lying around... rare with others that eat it promptly (for Chiton/protein recycling)> 2. Now I read that you're supposed to leave the molt in the tank.  Is that true? <true for above reasons> 3. I already got rid of it.  Is that bad? <no biggie> 4. Is 2 weeks considered fast? <fast?!?! 15 minutes is pretty good for most of us... 2 weeks (!), you are a god. Your poor wife/girlfriend.> 5. What would influence the speed of a molt? <diet, water changes and iodine for some/many> As always, thanks for all your help.  Rich <no... thank you for giving our team a good name <G>. Best regards, Anthony>

Emerald Crab Hello Bob, how are you today? <Bob should be doing wonderfully, he is diving in Cozumel. Anthony and I are holding down the proverbial fort for the week with Barb's help posting all our answers.> I bought a small emerald crab a couple weeks ago from the local fish store. He was missing one of his claws, due to a fight with one of the other crabs. They told me it would grow back quickly, <Back yes, but quickly no.> but after 2 weeks, I don't really notice anything growing yet (it is hard to tell, but there may be a stub starting to grow). I thought I'd ask you, since I know you all have lots of experience with marine life. Will the claw grow back, and about how long should it take? <Yes over the course of several molts. How often he grows and molts depends on your water quality and feeding.> Thanks much, Kevin D <You are welcome. -Steven Pro>

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