Piranha and snakes and Candiru

- Oh My!

The Candiru fish is South America’s aquatic red-headed stepchild. It is notoriously feared by the locals, even more than piranha or snakes, for its capacity to swim up one’s orifice (be it gills, urethra, anus, or exhaust pipe) where it deploys hooks and begins to engorge upon the host’s blood.


Figure 1. A Candiru's Nasal Barbs. These can also be found on the chin of te Vandellia. This photo was contributed by Anoar Samad, and the subject wa collected from a small Peruvian Village near Suni Maranho.

Once the Candiru has positioned itself in a host fish’s gills or another species orifice it will deploy these hooks to cause blood flow. Although the Candiru cannot forcibly extract blood it will drink that which flows out from wounds it causes.

Behaviours in the spotlight

In this website we will be investigating the following behaviors among the subfamilies which comprise the entity commonly known as the "Candiru."

Hitch-hiking – Hitch-hiking is described as an organism using another organism in order to propel itself without itself expending a large amount of energy. This form of parasitism provides the behaving organism the added survival advantage of the host’s protection from predators, greater dispersal, and better adaptability to changing environmental conditions. The Candiru has been documented as attaching itself to giant catfish which could travel great distances upstream.

Hematophagy – This behavior is strictly defined as the consumption of blood. The Candiru have evolved one-way hooks in order to anchor itself in its host while this process takes place. While this behavior provides a good source of protein and iron for the parasite, but the loss of blood is not the only detrimental effect for the host. The host also runs the risk of contracting some contamination from the parasite, for example malaria from flies. Vandellia are exclusively hematophagous.


My grandson once complained that he never caught anything when he went fishing. I told him that anyone can be a really successful fisherman once anytime they want in Argentina, just take a tinkle in the water. You’ll soon be telling your new friends in the medical ward about how you almost got away. –Martin Aszterbaum