Is this a sponge?

[plapczynski]

This was on a piece of LR with some shrooms. At first is was a small a my little fingernail. Here is a shot from May 31st. I have it circled in red.

 

Now here it is today about 4 times in size. It's translucent and is about 4 times in size.

 

 

Any ideas on what it is an if I should do anything about it?

 

Thanks,

 

Paul

[plapczynski]

Here's a clearer pic:

 

 

An a link to the full 1.7 mb image.

Full Image

 

Thanks.