That Fish Blog – Aquarium Advice and Information

Welcome back Brandon Moyer for Wednesday’s post.

Many aquarists are familiar with varying forms of symbiosis.  The most popular example I can give is that of the clownfish hosting in an anemone, providing the anemone with food and in return receiving protection from predators.  There are several different types of symbiosis, but both parties do not always benefit from these close relationships.

You may not be familiar with one creature that forms a symbiotic relationship with humans.  This relationship is considered parasitism, and we receive the poor end of the deal.  The species is called Vandellia cirrhosa, or candiru.  These fish live in the Amazon River basin, grow to about three inches in length, and prey on other species of fish.  They can detect the waste excreted by other fishes gills and follow the trail to find their prey.  Rather than eating the fish, they use barbs on their gill covers, or opercula, to wedge themselves under the opercula of their victim.  They then bite into an artery in the gills and drink the fishes blood.  They can completely gorge themselves with blood in as little as thirty seconds!

What makes the candiru even more horrifying is that their ability to detect waste from other fish also allows them to detect human waste, more specifically urine.  They have been known to follow the trail of urine of those who relieve themselves in the water and actually swim up the victims urethra!  If that doesn’t make you cringe, once in the urethra they are unable to turn around, and because of their spines they cannot back themselves out.  They eventually die in the urethra while the victim experiences swelling and obviously extreme pain.  The only way to remove the fish is through surgery. 

I hope you have enjoyed my first article on symbiosis.  Make sure to wear a bathing suit if you are ever swimming in South America.  Look for another blog on pistol shrimp and goby mutualism and pearlfish and sea cucumber parasitism.