Glochidium

These larvae are tiny and are typically between 100 and 200 micrometers, or approximately a third of the size of a grain of salt.

They can be round or have hooks, attaching to the gills, fins and scales of fish (for example to the gills of a fish host species) for a period before they detach, fall to the substrate and take on the typical form of a juvenile mussel.

Since a fish is active and free-swimming, this process helps distribute the mussel species to potential areas of habitat that it could not reach any other way.

[citation needed] Overexposure or heavy infections of glochidia may however greatly decrease the host's ability to respire.

Some mussels in the Unionidae, such as Ptychobranchus fasciolaris and P. greenii,[1] release their glochidia in mucilaginous packets called conglutinates.