Opportunist, or teeny-tiny predator? Mime crab.

[Tired]

Pardon the photo quality, but here is a mime crab, which is an animal roughly the size of a pea. A small pea. I just looked in my tank and saw this little guy eating an amphipod. Anyone wanna take a guess on whether he caught and killed that amphipod, or just found it dead? These little guys do grab pretty fast if something small whizzes by, so I wouldn't be too surprised if he actually killed it. Not really a problem, since I don't have any amphipod-sized fish, but interesting. It'd be a bit of a feat for something so tiny to manage to be any sort of predator. 

 

Bonus picture: 

My roughhead blenny being Menaced by a separate mime crab. Shortly after I took this picture, it walked over to her, poked her in the face until she moved out of its way, and strolled past to hide between some of the polyps. She was probably very confused as to why this rock was poking her in the face, and her nipping it in response did not bother it one bit. 

 

(Kindly ignore the cyano I have again. I think my carbon filter in my RODI unit needs swapping.)

[johnmaloney]

That is a good picture. I don't doubt they would eat one if they caught one, but that amphipod looks a little white and likely dead first. 

[Tired]

Yeah, that's probably not a fresh pod. Maybe it had a little tiny heart attack. 

 

Update on their opportunistic nature: the largest of the mime crabs went missing, and I found it in my filter compartment after probably a month. It's shed at least once (the loose carapace was in there), probably about doubled in mass, and looked well-fed and healthy. There are also notably fewer amphipods hiding in my filter compartments than there were before. I'm sure some of that is down to my fish snacking, but the only thing in that compartment for the crab to eat was pods. So, if you put a mime crab and amphipods in a small box, the crab will in fact grow in size. Seems they're capable of catching pods.

 

Hopefully it won't get much larger, I have some pretty tiny fish. It's still pretty tiny, and showing no interest in the fish, so I think we're good so far. It also seems to be leaving corals entirely alone, and I haven't seen any fanworms go missing, even the tiny ones. I'd imagine it just keeps having pods whizzing by its face and grabbing at them out of reflex, and apparently succeeding now and then.