Atlantic Marsh Fiddler Crab (Uca pugnax) burrow at low tide and fecal pellets
2014-8-15 Bombay Hook NWR, DE
they scoop mud into their mouths with their small claws (the big ones can't reach) - then strain out the nutrients and deposit the left-overs as fecal pellets
info
http://bugguide.net/node/view/361847
and
http://bugguide.net/node/view/1007878/bgimage