What Crab

[VR28man]

I think I got this crab from @reefcleaners as a spotted porcelain crab. But that crab ia up to 7-8mm wide, according to Wikipedia, and this one is easily 10 times the size. this one does appear to filter feed.



Sorry the picture is not very good. I may have to ask again when I can get a better pic.

 

[cloak]

Hmm, better picture without the blues on?

 

[ScottR]

I have two of these. They’re the size of a dime. One has been with me for over a year now and has grown quite a bit. Maybe nickel sized now. Sorry for poor picture but this is all I have.

 

[KJ]

Porcelain crab.

porcelain crab - - Image Search Results

 

[reefcleaners]

It is Petrolisthes galathinus, you may see different color variations with image searches. Scientists are still debating whether they should make them different species or just accept that there is variability within the species:

The Petrolisthes galathinus complex: species boundaries based on color pattern, morphology and molecules, and evolutionary interrelationships between this complex and other Porcellanidae (Crustacea: Decapoda: Anomura) - PubMed

While the amphi-American porcellanid crab Petrolistes galathinus has been traditionally viewed as a highly variable species containing several different color forms, we consider it to be a complex of at least 6 morphologically similar species with similar ecological requirements, but diagnosable...

www.ncbi.nlm.nih.gov

This ^ guy wants each different color to be its own species.

 

[VR28man]

John Maloney FTW- thanks! Well, at least it really was what you said it was, since I rechecked my order and it indeed was a blue porcelain crab not the other one.

The main author of that study is actually a girl, and in a quick google search for the species I found she'd done like half a dozen different articles on porcelain crabs. Some things I've found:

- there are of course many species
- galathinus as she says is a species complex
- galathinus can be found from like 1 m down to like 50m.
- porcelain crabs are not true crabs, but a kind of lobster that evolved into a crab. (which kind of makes sense when you look at them)

- they supposedly get up to 1" wide according to a lot of vendor sites, but mine is easily twice that. I'll try to catch him again and measure him.

 

[reefcleaners]

Oh I think I read it as Alexander at first. They usually measure the carapace in journals rather than the total width of the crab so you have to subtract the claws.

 

[VR28man]

Thanks again for the IDs. Unfortunately, the week after I posted this I had a massive tank crash and almost everything died.

I did recover their bodies. Interestingly, they had two different patterns (two different species?)

They were pretty cryptic; I saw them maybe once a month. But they survived well; they were at least six months in the tank, while I thought they had died long ago, they were still alive and had grown bigger since I got them. I did lose one of the three I originally ordered, and thought that I found enough empty carapaces, etc. to count all three dead but it seems those were just moltings. (I'm surprised that they look pretty lifelike. None of the other hermits, shrimp, crawfish I've previously had in this tank (or other tanks with the crawfish) molted like that.

The big one was big, but if measurement is only the carapace then he falls in the stated size range.

Anyway, cool critters regardless.

 

[Fresh_Water Reefer]

Thanks again for the IDs. Unfortunately, the week after I posted this I had a massive tank crash and almost everything died.

I did recover their bodies. Interestingly, they had two different patterns (two different species?)

They were pretty cryptic; I saw them maybe once a month. But they survived well; they were at least six months in the tank, while I thought they had died long ago, they were still alive and had grown bigger since I got them. I did lose one of the three I originally ordered, and thought that I found enough empty carapaces, etc. to count all three dead but it seems those were just moltings. (I'm surprised that they look pretty lifelike. None of the other hermits, shrimp, crawfish I've previously had in this tank (or other tanks with the crawfish) molted like that.

The big one was big, but if measurement is only the carapace then he falls in the stated size range.

Anyway, cool critters regardless.

what exactly happened to the tank?

 

[VR28man]

what exactly happened to the tank?

Tank Crash :(

So before my tank (29g/110L aqueon, no sump but with a was running OK, but loaded with algae and DOC, which I think I sort of had under control. Several SPS and the like were growing and had PE. Wednesday night I decided to do a massive clean out of algae on the tank walls and on rocks, to...

www.reef2reef.com

I need to do my final post-mortem, come to think of it........