How Transparent, ‘Vampire’ Catfish May Travel Unseen Through the Amazon River

The Amazon River basin’s most infamous bloodsuckers will not be all drama and gore in spite of everything. New findings recommend that some candiru—the vampire fish—could 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 repute. The tiny, wormy, almost 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 interested in the urine of individuals peeing within the river and swim up their urethras, turning into horrifically embedded. (Hard proof for this nightmare is more than a little dubious, and candiru don’t actually yearn for our pee.)

But the 9 or so species of candiru (subfamily Vandelliinae) are definitely vampires, beautifully tailored to sipping off their neighbors’ circulatory techniques. So when researchers found candiru being decidedly extra Mr. Rogers than Count Dracula, it got here as a shock.

In April 2019, Chiara Lubich—an ichthyologist on the Federal University of Amazonas in Manaus, Brazil—and colleagues have been surveying and accumulating fish species within the Rio Negro, a serious tributary river of the Amazon. As the workforce was eradicating and measuring fish caught of their nets, they noticed one thing peculiar clinging to the edges of a species of thorny catfish (Doras phlyzakion). Several 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 workforce discovered extra: 9 thorny catfish in complete, 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 edges of their our bodies. But they discovered an entire 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 could haven’t been feeding in any respect, simply hanging on like remoras on a shark.

“Apparently, [the candiru] hook up and travel with the host for reasons other than food,” says Lubich.

Such a benign interplay between candiru and bigger fish could imply the wee vampires have a extra different and sophisticated 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 powerful swimming talents, 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. Also, since candiru are slightly see-through, being pressed up in opposition to a much bigger fish’s physique could make it tougher for predators to identify them.

Larry Page, an ichthyologist on the Florida Museum of Natural History in Gainesville not concerned with this analysis, is intrigued by the concept the candiru are utilizing larger fish as transportation.

“It seems to me to be a plausible explanation,” mentioned Page, declaring that Lubich’s workforce didn’t essentially rule out the chance that the candiru do typically feed on the host’s pores and skin. “But it seems likely that they are using the larger fish to move long distances, or perhaps they are doing both: feeding and hitching a ride.”

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—could assist it grasp the edges of bigger fish.

Lubich factors out, nonetheless, that it’s attainable 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 workforce might retrieve them. Candiru can sense when a bunch is injured or in any other case indisposed and benefit from the scenario, defined Lubich.

Whatever the case, it’s clear that there’s extra to the biology of those unusual little parasites than simply bloodthirsty deviousness.

“I believe that much remains to be answered and known about this relationship, not only with thorny catfish, but the relationship between vampire fish and other species that we have not yet encountered and have not been reported on,” mentioned Lubich.