The Amazon River basin is home to approximately 15% of all freshwater fish species known to science, with an estimated 40% still to be described. Among them are such rare fish as those known locally as candiru, members of the Vandelliinae catfish subfamily. These are parasitic species that stick to the bodies of other fish and suck their blood, hence they are also known as vampire fish. Now a team of scientists has just discovered a new species of candiru, of the genus Paracanthopoma , which appears to be using its host in a very different way.
During a wildlife survey in a lake in the Demeni River basin, a tributary of the Negro River, scientists found these curious fish attached to the body surface of others, the Doras phlyzakion species. In all, they counted twenty candirus, one or two per host. In addition, they found that they did not attach to them in the gill area, as vampire fish usually do, but rather attached close to the lateral bone plates.
Vampire fish have long, robust snouts, with strong dental teeth that help them stay attached to their host’s epidermis and feed on their blood. However, when the researchers performed a gross analysis of the stomach contents of the preserved Paracantopoma samples, they were surprised to find no clotted blood, meat, skin, or mucus. This could indicate an interaction between the parasite and the host that is more benign than is normally attributed to vampire fish.
What benefit do they get?
“We believe that the association between candiru and host in this case could be commensalistic, rather than parasitic, because the hosts were not seriously harmed and the candiru apparently did not obtain any nutritional benefit,” explains Chiara Lubich, a researcher at the Federal University of Amazonas. and main author of the work, which is published in the journal Acta Ichthyologica et Piscatoria .
But what else would they look for on the back of the Amazon spiny catfish? One explanation could be that since candirus are small and almost transparent, it could be a way of camouflaging themselves from other predators. Another hypothesis is that they could be using their older cousins to be transported to longer distances that they could not cover by themselves, and thus get to safe places or new sources of food.
Referencia: Lubich CCF, Martins AR, Freitas CEC, Hurd LE, Siqueira-Souza FK (2021) A candiru, Paracanthopoma sp. (Siluriformes: Trichomycteridae), associated with a thorny catfish, Doras phlyzakion (Siluriformes: Doradidae), in a tributary of the middle Rio Negro, Brazilian Amazon. Acta Ichthyologica et Piscatoria 51(3): 241-244. https://doi.org/10.3897/aiep.51.e64324
Text: Pensoft Publishers
