Some things are easy to write about. For example, the world’s largest catfish was an effortless topic—what a great fish! There is plenty of information about the animal and its giant size makes it instantly fun and interesting (although the specie’s widespread decline does bring a sense of mounting unease). For a wide variety of reasons, other subjects are considerably more difficult to address. Sometimes the information is unavailable or the data is lurid and upsetting. In a poignant incongruity, one of these troubling topics happens to be the world’s smallest catfish, the candiru, which hails from the Amazon basin of Brazil.
The term itself “candiru” can mean either the species Vandellia cirrhosa, or it can refer to several genera of similar small catfishes. There is apparently even a genus “Candiru”. To put it bluntly the candiru is a vampire catfish. It enters the gills of larger fishes and sucks their blood–well actually, it doesn’t suck the blood as such. To quote “fishbase” an online fish resource, “[The candiru] bites mostly at the ventral or dorsal aorta arteries, and the blood is pumped into its gut by the host’s blood pressure. It does not need any special sucking or pumping mechanism to quickly engorge itself with blood, but simply uses its needle-like teeth to make an incision in an artery.” The candiru is small. Vandellia cirrhosa rarely exceeds lengths of 1-2.5 in (2.5-6 cm) with a width of 3.5 mm (although much larger specimens are known).
The junction of the Amazon River and the Rio Negro, (near Manaus, Brazil) is the principal haunting ground of the candiru. The catfish hides in the sand or mud. When prey swims by—either in the day or at night—the candiru uses its tremendous sense of smell and powerful eyesight to hone in on the other fish’s gills for a blood meal. The Candiru has backwards pointing spines behind its gill covers. It can lock itself into a victim’s flesh with these razor sharp rays.
The candiru is not picky about its blood source and this has made it one of the most feared fish in the Amazon. It has been known to enter swimming humans through various orifices or through open wounds. Lurid ethnological reports from as far back as the 19th century detail this fish’s intimate depredations of human hosts.
It is entirely whimsical—even childish—to speculate about whether the catfish is averse to garlic, possesses immortality, has become a hero to preteen girls, speaks with a strong Baltic accent, etc.