I think this might be a foram shell, but I am not sure. Diameter = 91 microns across at shortest point, 126 microns at longest point. Found while looking at sponge spicules in a bleach-digested sample. The numerous things in the background are spicules.
I think these are chiggers, but not 100% sure.
Tons of these on my hammock stand. Biggest ones are about 1 mm long.