Baby Urchins

[davelin315]

My kids picked up some common rock boring urchins or something along those lines when we were in South Carolina last November and we stuck them into a tank at the house.  They have since spawned (haven't seen it) as evidenced by the baby urchins on the glass... This is a cropped picture but the bubbles at the bottom of the shot are pretty much large microbubbles...

 

[pizzaguy]

Awesome

[YHSublime]

very awesome!

[dread240]

I'm not 100%, but I'm fairly certain they're hydroids

[Squishie89]

I'm not 100%, but I'm fairly certain they're hydroids

Agreed

 

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[lutz123]

Yeah, looks like hydroids. They will probably disappear on their own. For what it's worth, I have a baby urchin in my tank (probably hitchhiker on macroalgae) and it's perfectly formed and the body is probably half the size of a bb, carrying a tiny little shell on it's back. Super cute.

Edited March 7, 2014 by lutz123

[davelin315]

Was also my initial thought but based on movement and comparison to larval/juvenile shots of urchins I concluded urchin. Will watch them as I have had hydroid jellies before and these do not act like them at all in terms of movement. The cluster you see was spread out about 1" away from each other until I touched the glass and they all moved towards each other. Took a few minutes for them to clump together like in the photo.

[AlanM]

when I had tiny hydroids all over the glass in my new tank they seemed very stationary and didn't react to anything, so you could be right that these are different even though they look exactly like what I had. Mine were maybe 1/16 to 1/8 inch wide and looked kind of like mostly transparent tiny starfish or something.

[lutz123]

when I had tiny hydroids all over the glass in my new tank they seemed very stationary and didn't react to anything, so you could be right that these are different even though they look exactly like what I had. Mine were maybe 1/16 to 1/8 inch wide and looked kind of like mostly transparent tiny starfish or something.

My hydroids looked the same - especially the dots along the tenacles. While I don't know how old this baby urchin I have is, it is definitely to a stage where it looks like a very miniature adult. I haven't seen pictures of when they transition between free-swimming and fully formed, but the photo above isn't exactly what I would expect.

 

Go to this link and scroll to hydroids. See if it looks like what you are seeing. http://www.chucksaddiction.com/hitchodds.html

[davelin315]

Interesting, have seen that site before. May have to throw one under the microscope to look for tube feet. Still leaning towards urchins at this point based on behavior. When I have had hydroid jellies they have either not reacted to stimuli or they have swum away when disturbed.

[Origami]

Don't urchins go through a planktonic larval stage before settling, Dave? What's the probability that they would have been shredded in your return pump before settlement? Do you have a way of catching microphotographs of them while still on the glass?

[davelin315]

They do go through a plankton stage before settling - if you ever want to look at some interesting sites, check out the echinoblog by Chris Mahn (DC local @ Smithsonian Natural History).  He has some photos from other people - pretty neat!  This tank has a lot of flow but much of what goes through the pump doesn't get shredded - no "filtration" on this system, either, just rock and sand for biological filtration.

 

http://echinoblog.blogspot.com/2012/09/fantastic-pics-of-larvae-and-baby.html