also known as: Glochidium, freshwater mussel, Margaritifera , Western Pearlshell, Oregon Floater, Western Floater, Winged Floater, Yukon Floater, California Floater, Western Ridged Mussel, Anodonta, Gonidea
Glochidia are larval stage of mussels and clams, and can be a temporary parasitic inhabitant of fish. Some molluscs can lure fish close by exposing a piece of their mantle in the water and dose the fish with spawn when it strikes. The glochidia then encyst in the gill epithelium and grow, before dropping off within 10-30 days. In this manner the mussel can extend it's range using the fish for transportation, but can cause disease if present in high numbers on the fish.
When looking at a fish's gills, glochidia are visible as white spots that resemble trematode metacercarial cysts. Under the microscope, the spots are resolved to be larval bivalve shells.
West of the continental divide, there are 7 species of mussel that produce parasitic glochidia, and 6 of these are fgound in Oregon's fishes.
Fun fact: Mussels are a good indicator of ecosystem health and are one of the longest lived animals.