The Amazon River basin’s most infamous bloodsuckers might not be all drama and gore in any case. New findings recommend that some candiru—the vampire fish—might have a extra benign relationship with their host fishes, utilizing the hosts’ our bodies as transportation or safety from predators.
Candiru fish have a little bit of a fame. The tiny, wormy, practically clear catfish slide via murky Amazonian waters, wriggling their slender heads into the gills of a lot bigger fish. There, they latch on with robust enamel and guzzle blood like some form of tick/glass noodle hybrid. The fish are maybe most notorious for tales during which they’re drawn to the urine of individuals peeing within the river and swim up their urethras, turning into horrifically embedded. (Arduous proof for this nightmare is more than a little dubious, and candiru don’t actually yearn for our pee.)
However the 9 or so species of candiru (subfamily Vandelliinae) are definitely vampires, fantastically tailored to sipping off their neighbors’ circulatory techniques. So when researchers found candiru being decidedly extra Mr. Rogers than Depend Dracula, it got here as a shock.
In April 2019, Chiara Lubich—an ichthyologist on the Federal College of Amazonas in Manaus, Brazil—and colleagues have been surveying and gathering fish species within the Rio Negro, a serious tributary river of the Amazon. Because the group was eradicating and measuring fish caught of their nets, they noticed one thing peculiar clinging to the perimeters of a species of thorny catfish (Doras phlyzakion). A number of inch-long candiru—later recognized within the genus Paracanthopoma—studded the trout-sized catfish’s armored flanks, an odd location for a parasite that sometimes makes a beeline for the susceptible gills. The group discovered extra: 9 thorny catfish in whole, with a dozen candiru caught on.
The researchers introduced the candiru into the lab and checked out their abdomen contents with a microscope, questioning if the parasites have been feeding on the bigger catfish from the perimeters of their our bodies. However they discovered a complete lot of nothing. No blood, pores and skin, flesh, or mucus.
The findings—published in the journal Acta Ichthyologica et Piscatoria—recommend that the candiru might haven’t been feeding in any respect, simply hanging on like remoras on a shark.
“Apparently, [the candiru] hook up and journey with the host for causes aside from meals,” says Lubich.
Such a benign interplay between candiru and bigger fish might imply the wee vampires have a extra different and complicated relationship with hosts than beforehand appreciated, they usually are probably deriving some key profit past simply catfish-on-catfish cuddles.
The candiru could also be exploiting their hosts’ measurement and robust swimming skills, utilizing their our bodies as taxis to journey distances within the river that may be unattainable in the event that they tried to swim solo. Additionally, since candiru are a bit see-through, being pressed up towards a much bigger fish’s physique might make it tougher for predators to identify them.
Larry Web page, an ichthyologist on the Florida Museum of Pure Historical past in Gainesville not concerned with this analysis, is intrigued by the concept that the candiru are utilizing greater fish as transportation.
“It appears to me to be a believable clarification,” mentioned Web page, stating that Lubich’s group didn’t essentially rule out the chance that the candiru do typically feed on the host’s pores and skin. “But it surely appears probably that they’re utilizing the bigger fish to maneuver lengthy distances, or maybe they’re doing each: feeding and hitching a trip.”
There could also be “marked variation” within the consuming habits of the candiru subfamily, mentioned Lubich, of which Paracanthopoma is however one half. Some species have been discovered with their heads buried in a bunch’s stomach cavity. Others seem to additionally eat scales, mucus, and even a little bit of their host’s flesh. Paracanthopoma itself has the longest and strongest snout amongst candiru, mentioned Lubich, which—together with gripping enamel—might assist it grasp the perimeters of bigger fish.
Lubich factors out, nonetheless, that it’s doable the clinging could also be associated to how the thorny catfish have been caught. The fish have been caught within the web for hours earlier than the group might retrieve them. Candiru can sense when a bunch is injured or in any other case indisposed and reap the benefits of the scenario, defined Lubich.
Regardless of the case, it’s clear that there’s extra to the biology of those unusual little parasites than simply bloodthirsty deviousness.
“I consider that a lot stays to be answered and recognized about this relationship, not solely with thorny catfish, however the relationship between vampire fish and different species that we now have not but encountered and haven’t been reported on,” mentioned Lubich.