What kind of crab?

[Julie]

Anyone know what this little guy is?

Thanks,
Julie

[darkdep]

It's probably just me...but...where is the crab?

[AdamR]

Top centre, I think.

[Julie]

This is a test for those with 20/20.

Julie

[Julie]

Does Mithrax sculptus start out brown after shedding his skin?

Julie

[gvv]

Cannot be sure, just look here:
http://aquariacanada.com/forums/showthread.php?t=8959&highlight=box+crab

Regards

[rockgarden]

Congratulations Julie.  You got a hitchhiker crab.  I got thirteen of them as far as I could determine in the first 30 pounds or so of LR that I purchased.  You now have three or four choices.

1) Panic.  Worry about what it might do terrible some time down the road.  Take your piece of live rock out, Kill crab.

2) Panic less - Do as in #1 above but instead of killing him (or her - I got crabs of both sexes in my LR) put it in your sump if you have one or give it to someone else who has a sump and would like a crab in their sump.

3) Panic even less - Leave it alone.  Observe it constantly when you can find it (sit at night in your chair with your flashlight in your hand waiting for it to show itself).  Try to decide if it is hairy or not hairy (some threads say hairy ones might eat coral).  Get frustrated by it later in life when it is about an inch or so across and knocks your carefully placed coral bits off their rocks as it travels around at night.  Larger hermits and larger snails also rearrange things, by the way, but the hitchhiker crab normally gets the blame.

4) Don't do anything.  Just be happy.  IMO,  the presence of crabs and early appearance of other such hitchhiker wildlife (brittle stars, bristleworms) is a good indication that the rock was carefuly cured and not subjected to severe spikes in ammonia, and mis-treatment, etc during the handling and curing process.

Good rule of thumb IMO is that if it doesn't do anything bad in your marine environment, then it must be good or at the worst neutral. Crabs in general are good scavengers.  They will scrape away at your coraline algae a bit and chomp on any green algae tha strats to grow but once the tank is established, the impact is minimal.

I have encountered at least 15 or so hitchhiker crabs in my aquariums in the past year and so far the only 'problem" that I have encountered with them is that they knock over loose coral and rearrange smaller rocks from time to time. Some are hairy, some aren't, at least one is red and one is pure white.  In fact I jsut rearranges a 25 gallon tank lst week that has been up and running for about 5 months.  There was a hitchhiker crab in that tank all than time and I had never seen it. Lots of such surprises from time to time in the marine aquarium.

Ron

[Julie]

 not panicking - was thinking mini crab legs.
Say are you in tower c?

Julie

[rockgarden]

Looks like you might have got yourself a very nice piece of rock BTW.

Ron

[Julie]

Here's another piece:

[rockgarden]

Nope, not in Tower C.  

Decided to take early retirement in July.  Now have more time to look after 15 or so aquariums and post responses to lots of questions on various bulletin boards re FW and SW fish, photography, gardening, and all sorts of other areas that I am interested in.

When it snows, I might start thinking about my next career and start sending out resumes (almost sent one out this weekend but I restrained myself) or consulting or, heaven forbid, looking for part-time work in a fish store but at the moment the weather is too nice to think about working again. I'm looking forward to diving on a real coral reef in January. After that, who knows.

In the meantime, I'll content myself with counting hitchhiker crabs , raking leaves and cutting grass.

Ron

[rockgarden]

It looks like the second piece has mushroom corals growing on it already.  If that is the case, then you have done really well.  Did you buy it from LFS or did you get it from someone's established tank?  In either case it looks like a great piece to start a tank with. Nice coralline colouration is a good starting point.

[Julie]

Ray's established tanks - numero uno.

Julie

[Julie]

Sounds nice - which reef?

My gf is a chem. eng. in pq.

Julie

[rockgarden]

Back to the other part of your crab question.

When crabs and shrimp molt they leave behind their exoskeleton (outer shell).  For a short period after the exoskeleton has been shed, that exoskeleton can look almost as real as the crab or shrimp itself.  No need to remove it from the tank.  Other creatures in the tank will consume it.

After shedding their exoskeleton, the creatures start to regrow a new, slightly larger one.  Until that new exoskeleton is hardened up, the creature is very vulnerable to attack and will tend to hide out in a safer location within the rockwork.

A bit frightening when you wake up in the morning, find a cleaner shrimp exoskeleton floating around near the front of the tank and then don't see your shrimp for a couple of days.  You think.  Oh, no I've lost my $$$ shrimp.  That darn ### crab must have eaten it! A day or so later you breathe a sigh of relief when the $$$ shrimp reappears. Everyone blames the hitchhike crab for everything!  

Ron

[mseguin]

That first one looked like an emerald crab, did  it not?

[Julie]

It was brown though, but it just shed its skin.

Julie

[gvv]

A bit frightening when you wake up in the morning, find a cleaner shrimp exoskeleton floating around near the front of the tank and then don't see your shrimp for a couple of days.

:lol:  :lol:
I once got "ghost shrimp": shrimp changed exoskeleton while sitting on the rock and it was left there untouched! So I was really surpised to see 3 shrimps while I only have 2. But than I noticed that the back cover is slightly opened and there are nodoby inside.

As for crab you have: should agree with Ron, as you should worry only if something wrong is happening. It is very difficult to classify most of invertebrates and some of them were found not in wild but in reef tanks! My favourite time is at night when all of the wierd creatures start crawling/floating around.  :shock:  

Regards

[gvv]

Don't want to hijack the thread, but...
Concerning the creatures I managed to take a shot of two but others do not like when I appear with lights

[Julie]

test