Arrow crab

[Ddalton]

My arrowcrabs name is butthead.  He was suggested to me by my local fish store for a cleaner.  I had gone in for a emarld crab having had kept them in the past with success. But going on there advice I purchased Butthead a cleaner and so much more.  Notably my two fish avoid him since he wildly kicks anything that approaches (including hands).  But he's eaten all the algea of my star polyps and live rock. So far so good great cleaners.

[WV Reefer]

2 minutes ago, Ddalton said:

My arrowcrabs name is butthead.  He was suggested to me by my local fish store for a cleaner.  I had gone in for a emarld crab having had kept them in the past with success. But going on there advice I purchased Butthead a cleaner and so much more.  Notably my two fish avoid him since he wildly kicks anything that approaches (including hands).  But he's eaten all the algea of my star polyps and live rock. So far so good great cleaners.

 

Never trust a crab.  

[BustytheSnowMaam]

Hmmm....arrow crabs aren't algae eaters.  They are a useful member of the CUC because they do eat leftover food.   They eat bristle worms- they'll hold one in a claw for days and slowly pull it apart over time.  They'll also eat feather duster worms.  If you look at the size and style of their claw, you can see that it's designed to extract food from crevices.  They leave fish alone and I've never had one damage corals.  

 

Here's a pic of mine from way back when eating a bristle worm.  

[WV Reefer]

59 minutes ago, tashayar said:

Hmmm....arrow crabs aren't algae eaters.  They are a useful member of the CUC because they do eat leftover food.   They eat bristle worms- they'll hold one in a claw for days and slowly pull it apart over time.  They'll also eat feather duster worms.  If you look at the size and style of their claw, you can see that it's designed to extract food from crevices.  They leave fish alone and I've never had one damage corals.  

 

Here's a pic of mine from way back when eating a bristle worm.  

I’ve never heard them called “cleaner” before either...... unless they mean cleaning out anything they can pull out of the rocks!

[BustytheSnowMaam]

6 minutes ago, WV Reefer said:

I’ve never heard them called “cleaner” before either...... unless they mean cleaning out anything they can pull out of the rocks!

Yep!  And they are pretty neat.

[RayWhisperer]

I'm gonna hafta agree with Tasha and WVR. Never heard of an arrow crab eating algae. Though I can't really agree with the statement of them being a useful member of the CUC. Bristle worms are beneficial, arrow crabs eating them isn't.

[BustytheSnowMaam]

I think when the crab breaks off pieces of the worm, those pieces can regenerate into new worms.  

[RayWhisperer]

Well, I have no knowledge of bristleworm physiology as it pertains to regeneration. However, if they are anything like earthworms, the whole regeneration myth is complete crap. 

 

With earthworms, if you cut one in half, you'll most likely get two halves of a dead worm. Both parts CAN regenerate if you cut very near to the head, and have ideal conditions for both parts to live. They won't, however, both regrow into full size worms. Both will be severely stunted. Now you know more about earthworms than you've ever wanted to.

[BustytheSnowMaam]

I noticed when my arrow crab would rip up bristle worms that the pieces seemed to still be living.  In some polychaete worms (earthworms are oligochaetes) a single segment can regenerate into an entire worm.  The only thing I could find online is this paper https://academic.oup.com/icb/article/46/4/508/635658/Distribution-of-segment-regeneration-ability-in .  I think if I knew the genus and species name of the bristle worms most commonly found in tanks I could get a better idea of its regenerative abilities (or lack thereof).  All in all, I don't think an arrow crab with extra fish food to eat will wipe out a healthy population of bristle worms.  I always had plenty despite the crab.  

[Ddalton]

Well two days ago I noticed what thought to be a perfect she'll of the arrow crab.  Later  that day i saw him pull one of his claws off and throw it.  My cleaner very quickly came and grabbed it and retreated with claw into his corner, like a dog with a bone. The cleaner shrimp had molted the previous night. Haven't been able to find second claw, he's eating still directly from dropper I feed with.