Myxozoa. It means Slime Animals!
These creatures are actually members of the phylum cnidaria alongside jellyfish and coral.
They’re parasites who start out life as spores in the gut a of worm. When the spores enter a fish, they turn into a triactynomyxon spore which fires a kind of non-venomous stinging cell into the fish’s skin.
Sporoplasm enters and spreads into the tissue of their new host. They now grow into sacks of cytoplasm which give rise to a new generation of spores, ready to enter the bodies of scavenging worms when their fish dies.
Aren’t they the cutest little parasites you ever saw?
Images: Ivan Fiala