From: itannman@boris.ucdavis.edu (Ann Mansker)
Subject: Critter of the Week: Vandellia cirrhosa
Date: 28 Jul 1998 00:00:00 GMT
Newsgroups: ucd.life

The candiru (Vandellia cirrhosa) is one of the many catfish native to
the Amazon River.  It is a small, slender fish, ranging in size from 2.5
to 6 cm, with a thickness of about 3.5 mm.  The image at  
http://www.si.edu/organiza/museums/zoo/hilights/lectures/fish/e7.jpg is of
a fairly large speciman; probably too large to be of much concern.

Candiru, despite (or perhaps because of) their diminutive size, command
great respect among Amazon natives and visitors.  The fish typically
survives by parasitizing larger fish.  The candiru achieves this by
detecting the "taste" of the water stream passing through it's victim's
gills and following it upstream.  When it finds the source, the candiru
slips under the target's gill flap and extends spines from around its
head to hold itself in place.  The sharp spines also start a flow of
blood, upon which the parasite feeds.

Candiru are just as willing to feed off of other creatures.  Humans become
involuntary hosts by urinating while wading or swimming in
candiru-infested areas.  The fish follows the stream to its source and
enters the victim's body through the urethra.  When it is no longer able
to move forward, the fish extends its spines and lodges itself firmly in
place.  This is reported to be excruciatingly painful.  Treatment consists
of surgical removal; if not performed in time, the patient usually dies.

The candiru is the only known vertebrate parasite in humans.