Dark Banquet - Bill Schutt [91]
Physically, candirus are nowhere near as nasty looking as a decent-sized piranha. They are eel-like in appearance with their dorsal, anal, and pelvic fins set far back on their translucent bodies, close to the tail. Their small eyes are located near the top of their dorsoventrally flattened skulls. Candirus have tiny sensory barbells (unlike the prominent whiskerlike structures found in many catfishes), and they lack the stout and often dangerous dorsal and pectoral spines that have punctured countless anglers.
Although most people would consider this a good thing, the chances of ever seeing a candiru in the wild are quite low—that is, of course, unless you regularly fish the Amazon River and its tributaries with a cow lung tied to a piece of rope (a technique detailed in an article published by Kenneth Vinton and W. H. Strickler in 1941). The tiny fish usually remain hidden in the sand, mud, or leaf litter. They’re also found in shallow, fast-moving water. This secretive lifestyle (which we’ve seen in other vampires) appears to be one of the reasons why studies on topics like the candiru’s reproductive biology as well as many other aspects of its behavior remain sketchy or nonexistent.
Vendellia cirrhossa is probably the best-known species of candiru, although Vendellia wieneri has the coolest name. Candiru (which typically range from one to six inches in length) prey on larger fish and they feed by wiggling under their hosts’ gill covers (opercula), the flaplike structures that shield the gill chambers. These opercula open and close as the fish breathes, and once inside, the tiny vampires secure themselves to the delicate gill lamellae (which are arranged like pages in a book) by a series of tiny, backward-facing hooks. These integumentary teeth or odontodes (sometimes called denticles) are found in patches around the candiru’s head (including their own gill-covering opercular and interopercular bones). Once secured, the candiru utilize two or more rows of needlelike teeth to bite through one of the blood vessels that function in gas exchange between the feathery, high surface area gills and the fish’s body.*145 Apparently, muscles in the candiru’s mouth and pharynx pump the blood into the digestive tract.†146
The candiru feeds for somewhere between thirty seconds and nearly three minutes, the blood clearly visible through its engorged, nearly transparent body. Since they sometimes feed in groups, the blood loss and damage to the host’s gills can be considerable as pieces of shredded gill lamellae are sliced off by the teeth and rasped off by the odontodes.
Do candirus ever swim up the human urethra? Apparently, it does happen, although thankfully, occurrences are extremely rare. There have been numerous anecdotal descriptions, reviewed in depth by Spotte, but the first confirmed attack was reported by Drs. Spotte, Paulo Petry, and Anoar Samad at the 2001 meeting of the American Society of Herpetologists and Ichthyologists. Dr. Samad, a urologist, had treated a young man who showed up several days after a swim in the Amazon during which he had decided to remove his swim trunks before urinating.
On 28 October 1997, one of us (Samad) attended a 23-year-old man who sought medical attention with extreme swelling and bleeding, having been attacked by a candiru. After extraction by endoscopy, the candiru measured 134 mm SL and 11.5 mm width across the head. Perfusion of the urethra with sterile distilled water prior to endoscopy induced immediate and pronounced scrotal edema. The candiru’s penetration had been blocked by the sphincter separating the penile and bulbar urethras. Subsequently, the fish had bitten through the tissue into the corpus spongiosum, and the opening had allowed the perfusate to enter the scrotum. Some coagulated