September 7, 2001

Dear Cecil:

This is in reference to your column "Can the candirú fish swim upstream into your urethra?" (May 19, 2000). I recently heard a talk by a visiting scholar who was researching the candirú. The speaker was collaborating with a South American medical doctor who completed a candirú removal operation in 1997. The fish had entered the (male) patient's urethra, had been stopped by the urethral sphincter (if that's the right term), and had turned at a right angle and burrowed into the scrotum. The fish had died, and the subsequent relaxation of its spines facilitated removal. A photograph of the removed fish and part of the affected area (!) was presented. According to the speaker, the patient claimed the fish had swum out of the water up his urine stream. I thought this might be of interest.

— zut, via the Straight Dope Message Board

I'll say it's of interest. In my original column I expressed skepticism about Willy-in-the-willy, noting an absence of firsthand or even secondhand accounts. And now here's a guy with eight-by-ten glossy photographs! I've been in contact with Paulo Petry, the scientist you heard, who related the following astonishing tale. Warning — gross-out quotient: high.

Petry is an expert in neotropical ichthyology and vice president of Bio-Amazonia Conservation International, a not-for-profit conservation group. While working in the Amazon city of Manaus, Brazil, he noticed a hubbub in the press about Anoar Samad, a urogenital surgeon who'd performed the world's first confirmed removal of a candirú from a human penis. What's more, Samad had a live patient and a dead fish to prove it. Petry decided the world needed to know about this. Here's an except from an article the two are coauthoring with fish physiologist Stephen Spotte:

On 28 October 1997, one of us (Samad) attended a 23-year-old man from the town of Itacoatiara on the Amazon River who sought medical attention with obstruction of the urethra, having been attacked by a candirú. Prior to being attended, the patient remained untreated for three days and was only administered medication for pain. By the fourth day the patient presented with fever, intense pain, scrotal edema [swelling of the scrotum], and extreme abdomen distention from urine retention. Surgical removal of the fish was considered, but rejected in favor of endoscopy [insertion of a TV-equipped tube into the urethra]. The patient was anesthetized with 5% lidocain and the procedure was performed. The fish was grasped using an alligator-clip attachment on the endoscope and removed in one piece. Fortunately the fish was dead, and decay was beginning to soften its tissues. Tension on the spines had relaxed in death, and they no longer gripped. Had the candirú been alive, its removal would have been more difficult and resulted in greater trauma to the patient. The fish penetrated the victim's urethra while he was standing in the river urinating, actually emerging from the water and entering his penis, filling the entire anterior urethra [emphasis added]. He reported trying to grab hold of the fish, but it was very slippery, and it forced its way inside with alarming speed. The candirú's forward progress was blocked by the sphincter separating the penile urethra from the bulbar urethra. With the passage blocked, the fish had made a lateral turn and bitten through the tissue into the corpus spongiosum, creating an opening into the scrotum. Perfusion [flushing] of the urethra with sterile distilled water prior to endoscopy induced further immediate and pronounced scrotal edema, making it evident that the opening had allowed the perfusate to enter the scrotum. Although the patient had remembered the fish as being small, after extraction it measured 134 mm (5½ in) [long], with a head width of 11.5 mm (7/16 in) … Some coagulated material was removed, revealing a wound on the bulbar urethra of 1 cm in diameter and associated with a small amount of local bleeding. Although the patient suffered immediate trauma, no long term effects of the attack were noticed 1 year after the incident.

Petry insists this is no joke. The operation is well documented, with photos, a videotape of the procedure, medical reports, and of course the fish, which was donated to an Amazon research institute. (The species couldn't be identified precisely due to decay. I can't decide what's worse: having a live fish inside your penis or a rotting dead one.)

"The description of the case follows exactly what the patient said," Petry tells me. "According to him, he was standing in the water thigh deep, urinating with his penis out of the water yet close to it. The fish jumped and entered his urethra. He repeated the same version more than once when asked to describe the incident to Dr. Samad."

Research by Petry and Spotte found no indication that the fish is particularly attracted to urine. Petry adds, "The only way that the fish could enter the urethra is while it is expanded during urination, otherwise I don't think it could move in." One shudders, but I thought you'd want to know.

— Cecil Adams

Cats seem pretty apathetic about a lot of things. You might think music is one of them. But according to a new study, it's not that cats don't care about music – it's that they don't care about YOUR music. So what kind of music do cats appreciate? We're so glad you asked.

House cats often appear aloof and indifferent toward their human companions. But it's not just … Read more Read more

A recently published study in the journal Applied Animal Behavioral Science concludes that cats prefer "species-appropriate" music.

"We have developed a theoretical framework that hypothesizes that in order for music to be effective with other species, it must be in the frequency range and with similar tempos to those used in natural communication by each species," write study authors Charles Snowdon and Megan Savage, both psychologists at the University of Wisconsin, and David Teie, a musician who has collaborated with Snowdon on the study of species-specific music for the better part of a decade. For instance, Snowden and his colleagues propose feline-appropriate music might mimic the rhythmic and tonal qualities of a purr, or a kitten suckling at its mother's teat.

It's probably one of the most comforting sounds in the world if you like cats. A purr feels… Read more Read more

Here's an example. The following clip is from a song titled "Cosmo's Air." It was composed by Teie. The tune, the researchers write, "has a pulse related to purring of 1380 beats per min... with melodic sliding frequencies covering 44% of the sample" (sliding frequencies are found in a variety of cat vocalizations, but aren't commonly found in human speech):

To test their hypothesis that cats prefer music specially designed for their listening pleasure, the researchers played "Cozmo's Air" and one other example of Teie's feline-specific music in counterbalanced order with two examples of human music (viz. Johann Sebastian Bach's "Air on a G String" and Gabriel Fauré's "Elegie") for 47 different domestic cats, and evaluated feline behavior in response to each piece.

"Cats showed a significant preference for and interest in species-appropriate music compared with human music," the researchers write. Expressions of approval included purring, and orienting the head toward, moving toward, rubbing against, or sniffing the speaker from which the music was emanating. "The results suggest novel and more appropriate ways for using music as auditory enrichment for nonhuman animals," the researchers conclude.

That co-author David Teie sells feline-specific music on his website, musicforcats.com, is sure to raise flags for some of you. I know it did for me. That said, the authors note that Teie was not involved in the design of the study. Neither was he involved in the research or data analysis portions of the investigation. Cat behaviors were scored during music-exposure sessions by one observer, while video footage was independently scored later, by a second person – though the study makes no mention of who, specifically, did this scoring, or whether they were blinded to the species specificity of the music being played.

It's also worth mentioning that Teie's interest in species-specific music predates the cat-study by a number of years. He's also interested in species besides cats. His first major contribution to the scientific literature came in 2009, with a study, published in Biology Letters, that showed small monkeys called cotton-topped tamarins "were generally indifferent to playbacks of human music, but responded with increased arousal to tamarin threat vocalization based music, and with decreased activity and increased calm behaviour to tamarin affective vocalization based music." According to Teie, "it marked the first controlled study that showed a consistent and appropriate response to music from any species other than human. I'll be the first to admit I didn't exactly do a deep dive looking into this, but, best I can tell, his claim holds up.

Anyway, at the very least, Teie and Snowdon's most recent study gives you a chance to experiment with your pets at home. Teie has samples of the music used in the study on his website, along with music that incorporates other feline-specific sounds not directly associated with communication, including "stylizations of some of... animal calls that are of great interest to cats." Consider, for example, this clip from a cat-song called "Spook's Ditty," which incorporates noises resembling birdcalls. "A little like sonic catnip," Teie writes on his website, "ditties are meant to arouse interest and curiosity":

I don't own any cats, but when I played this song for my dog (a pointer-breed with a known affinity for birds and their noises), her ears perked right up at the sounds resembling bird calls. Data point of one and all that, but feel free to try it on your own household animals with this and other samples available on Teie's website.

Read the full study in Applied Animal Behavioral Science.