A few years ago, biologist Carlos A. Lasso did a double take when he examined what turned out to be a strange-looking worm with a magnifying glass. He thought the object could have been “the root of a plant, plant stem or other unknown organism”.
During the Covid-19 pandemic, he sent the sample to an expert. A few months later, specialist Mario Londoño, from the University of Antioquia in Medellín, confirms the discovery: it is a freshwater worm from the depths of the Orinoco, a 1,700 mile long river. which forms part of the border between Venezuela and Colombia.
“Freshwater species are usually found near the coast. What’s remarkable is that I found these worms in deep, fast-moving water, more than 600 miles from the ocean,” says Lasso.
Another thing that caught the biologist’s attention was that the worms “were attached to the molluscs.” According to Lasso’s hypothesis, this would imply a relationship between invertebrates.
For more than 12 years, Lasso – a native of Madrid who has worked in Latin America for nearly four decades – has been carrying out surveys to study the biodiversity of aquatic fauna and hydrobiological resources at the mouth of the Orinoco. It is based in the Colombian municipality of Puerto Carreño, capital of the department of Vichada.
“We take advantage of the dry season, from January to April – when the level of the river does not exceed 30 feet – to do the dives”, explains the researcher, affiliated with the Humboldt Institute in Bogotá.
Lasso and Londoño believe that the specimen – unknown to the scientific community until now – belongs to the genus Manayunkiaof the Sabellidae family. It is “a vector of parasites in fish, such as salmon, which could be important for the aquaculture industry”, explains the biologist. He also thinks that in addition to its parasite-trapping abilities, the worm could constitute evidence “of the marine transgressions and regressions suffered by the Amazon and Orinoco regions”.
Some hotly debated scientific theories suggest that a wide, shallow sea covered large parts of South America – including the Amazon and the Orinoco basin – for millions of years. According to a 2017 study published in the journal Scientists progress, the Caribbean Sea bathed the freshwater territories of present-day Venezuela and Colombia twice during the Miocene, the first geological epoch. This thesis would explain the evolution and distribution of fauna in the region.
“Like the Amazon, the Orinoco – which can reach over 300 feet in depth – has been subject to changes in its ecosystem, leading to the extinction of some species and the survival of others by adapting to the new conditions. This is already evident in jellyfish or freshwater stingrays, whose ancestors have been found in these rivers,” says Lasso.
With more than 1,650 fish recorded to date, one of the characteristics that characterizes the Orinoco ecosystem is its astonishing biodiversity. According to the Spanish biologist, “every time an exploration is carried out in this region, something new is discovered. Finding unknown organisms in tropical South American environments is relatively common.
To find new wildlife, which often remains hidden in unexpected places, Lasso goes beyond standard collecting methods. “I do nighttime sampling at great depth with zooplankton trawls, with light traps and underwater dives,” he explains. Lasso has a habit of patiently inspecting the strangest habitats, often planting his magnifying glass inside trunks and roots.
“At [Humboldt Institute], in collaboration with the University of Los Andes, we are conducting deep-sea studies of environmental DNA, known as metabarcoding,” he explains. This new technique – which studies free-living genetic material in ocean ecosystems and in many aquifer systems – is a non-invasive method to assess the composition and distribution of organisms in various habitats.
Lasso and several specialists from the University of Antioquia have formed a working group to continue gathering knowledge about the new worm. “I am in charge of collecting ecological information…the other group focuses more on the genetic aspects [of the worm]“, explains the biologist.