Cryptocaryon irritans

A description of Cryptocaryon can be found here ( scroll down to find Crypto)

Note that unlike amyloodinium, cryptocaryon can be seen with the naked eye, particularly on the gills where the crypto looks like white pin heads on the bright red gills

Click here to see a 40 X photo of crypto in a gill filament of barra. Often the crypto will be rotating inside the sac, and it is no wonder that this parasite is so irritating to the fish.

Here is a 40 X photo of a barra gill filament where the parasite has already abandoned the gill, leaving an empty sac where it had matured over a few days.