As I’ve said before, UCA can mean Universalist Church of America. That said, I think I’ve found the Universalists (generally) a much-needed mascot.
My friend here is a male example of Uca pugnax, the mud fiddler, which, as it happens, is also native to the salt marshes of this region. Fiddler crabs are in the genus Uca, and so any would be appropriate, but pugnacious fiddler crab seems particularly apt. 
I got this image from a U.S. government website, so I trust it isn’t under copyright, but fair-is-fair, and so I’ve made a link to the site so you can learn more about this lovely beastie.
Link: NOAA Coastal Services Center page on fiddler crabs