Well... it's probably an animal. Weird hard blob.

[Tired]

Came in on some Gulf rock. About an inch and a half across, hasn't changed visibly since I got the rock in November. It seems to be pretty resistant to algae growth, and it doesn't respond to light, touch, food, or anything else. It looks to have some sort of internal structure, a short distance under the surface. Very firm to the touch, like extremely dense rubber. 

 

Any guesses? I'd say maybe some sort of tunicate, except that I don't see anything that looks like a breathing intake. It's all completely smooth. I found an article about "sea pork" (tunicates) washing up on beaches, and some of the photos look similar, but they don't mention the texture of the things. I'm sure this whatever-it-is is harmless, considering it seems to be doing nothing, I'm just curious about it. 

 

[mcarroll]

I was thinking "spicules" when looking at that structure.   Some kinda of baby leather coral?

[Tired]

Wouldn't a leather coral have somehow unfolded itself to the light, though? It also seems to be a lot firmer and more smooth than a leather coral, which, if I remember right, is at least a reasonably squishy entity. This doesn't give at all if I poke it.

[WV Reefer]

3 hours ago, Tired said:

Came in on some Gulf rock. About an inch and a half across, hasn't changed visibly since I got the rock in November. It seems to be pretty resistant to algae growth, and it doesn't respond to light, touch, food, or anything else. It looks to have some sort of internal structure, a short distance under the surface. Very firm to the touch, like extremely dense rubber. 

 

Any guesses? I'd say maybe some sort of tunicate, except that I don't see anything that looks like a breathing intake. It's all completely smooth. I found an article about "sea pork" (tunicates) washing up on beaches, and some of the photos look similar, but they don't mention the texture of the things. I'm sure this whatever-it-is is harmless, considering it seems to be doing nothing, I'm just curious about it. 

 

Hmm.  Very cool. 
 

……..the insides look like mesenterial filaments 

[PJPS]

Pretty funky as far as weird blobs go 👍🏻. I’ll join the ID search as I have no clue.  Pitty Veron’s reference books are useless for trying to ID something in front of you.  It’s great if you can memorize it all though 🙄.  I’m going to see if my kung fu can beat a weird hard blob’s anonymity.  My 💰 is on the blob, I suck at weird stuff 🙁

[ml86743]

Wonder if it could be some sort of egg casing? 

[PJPS]

It’s not the same, but NOAA is stumped by something similar https://divernet.com/scuba-news/blue-goos-urchins-with-hats-but-why/

 

a less accurate visual AI match https://www.health.harvard.edu/blog/erectile-dysfunction-drugs-skin-cancer-worry-201406057197

 

Also, I’m 99% that whatever it is, it’s on what they seem to call “rock”.

 

e: kidding aside, perhaps a freaky sponge? https://universe-review.ca/R10-33-anatomy01.htm

 

Internal structure, density works… worthy of a bit of investigation.  I’ll keep looking unless you can rule out weird sponge?

[PJPS]

OK, after reading that detailed sponge anatomy write-up, I’m reasonably confident it’s some sort of sponge.  If your tank is keeping it alive without trying, it speaks well of your general husbandry.  Relatively dense sponges can bail in fragile tanks (I didn’t buy a bright red sponge and lose it one time)

 

particularly

 

• Musculo-skeletal - The wall of a sponge contains 3 types of cells. The outer cells are flattened epidermal cells. The inner cells are collar cells with flagella, whose constant movement produces water currents that flow through the pores into the central cavity and out through the upper opening of the body, called the osculum. The mesohyl is a gelatinous layer between the outer body of the sponge and the spongocoel (the inner cavity). The "skeleton" of the sponge is composed of tiny needle-like splinters called spicules (composed of glass or calcium carbonate), a mesh of protein called spongin, or a combination of both.

[Tired]

Yeah, I'm leaning towards it being some sort of odd sponge. It's too unreactive and free of holes to be a tunicate, though I do have plenty of those in here, in a variety of tiny species. 

 

I really can't claim any credit- all I've done is fill the tank with water. If it is actually doing well, and not just dying very slowly, that's courtesy of the ~40lbs of live rock in there with it. It seems to be doing okay so far. 

[LazyFish]

I would also guess something to do with sponge keep an eye on it and let us know how it develops. I love all the weird hard to I'd critters that show up in peoples tanks.

[Tired]

I've been directed to the Chicken Liver Sponge, which definitely has plenty of similarities. I'm deciding that this is probably something in the general vicinity of one of those.