Daniel Machado said:The little catfish simply followed the ammonia from the urine (that guy was urinating in the river) and swam INTO the urethra. The "host" tried to hold the fish, but didn't worked. These fishes normally find their host fishes following the ammonia flow that comes from the gills, and seek the gill arteries, where they feed.
best regards.
Daniel.
So he was under water peeing and it swam in? Wouldn't you feel it? does it swim in small and grow or it swims in that size?