The Island of Guernsey, known for being a tax haven in the English Channel, became the adoptive home of an illegal immigrant eight years ago. The stealthy visitor from Brazil settled into gardens and nurseries in that British Crown dependency in the early months of 2008. Sometime later, probably in the midst of a European tour, it was also seen in similar locales in Great Britain, Spain, Italy and France. The mysterious refugee was at first mistaken for a close relative with similar features, known as Obama marmorata.
In April 2016, the traveler’s true identity was revealed, based on the available information, through genetic analysis and X-ray computed microtomography. Named Obama nungara, this is a species of land planarian measuring 10 centimeters long, a type of flatworm found in green areas in Guernsey, which is situated between England and France. “It is the first species of planarian found in Europe that is neotropical—native to the area encompassing southern Mexico and Central and South America,” explains biologist Fernando Carbayo of the School of Arts Sciences and Humanities at the University of São Paulo (EACH-USP). Carbayo is primarily responsible for the taxonomic classification assigned to the worm found in Guernsey. The official description of the new species appears in a paper published in the Zoological Journal of the Linnean Society in May 2016.
The paper lists 10 anatomical features that differentiate the two Obama species, which usually share the same environment. “You can find both species side by side under a rock in the Atlantic Forest biome in Santa Catarina State,” the researcher says. O. nungara is generally smaller than O. marmorata. Its body is 72% of the size of the other species on average, and it has a darker color. O. nungara displays shades of golden yellow or a honey color, with tiny black streaks. O. marmorata is light brown, with brownish-green streaks. Planarians have sightless eyes, but they move around using light-and-dark sensors that are distributed distinctly all over their bodies.
In addition to listing these more obvious features, the paper mentions other, more specific differences between the two planarian species, some of which are linked to the male and female reproductive apparatus. These features can be studied only by making histological sections of the animal’s tissue, or through X-ray computed microtomography. It is interesting to note that most planarians are hermaphrodites, and in that regard, those of the genus Obama are no exception. Scientists have also found that their DNA exhibits particular features that support classification of the two forms of planarians as separate species.
Scientists’ efforts to identify this species of Brazilian planarian native to the Atlantic Forest and now found in Europe have not been driven solely by academic curiosity on the part of those who specialize in the study of these worms. Global movement of people and goods has promoted the worldwide dispersal of plants and animals that were once restricted to certain parts of the planet. “To introduce an exotic species into a new environment, all you need is a potted plant containing one planarian,” Carbayo notes. The arrival of species in places where they have never been before introduces both ecological and economic concerns. The list of the 100 most dangerous invasive organisms drawn up by the International Union for Conservation of Nature (IUCN) includes Platydemus manokwari, a type of land planarian native to New Guinea. In early 2014, it was found in a greenhouse in the northern French city of Caen, causing apprehension among environmentalists and escargot farmers. The reason for their concern was the fact that P. manokwari’s basic diet consists of land slugs and snails, and it decimates their populations wherever it turns up. The species has been recorded in 22 countries, including the United States, where it has been found in Florida. It has not yet been seen in Brazil.
A worm diet
The fear is that O. nungara could follow in the steps of the planarian species from New Guinea, and that is a possibility. “O. nungara appears to be a generalist planarian, meaning that it eats different plant types, explains biologist Ana Maria Leal-Zanchet of Vale do Rio dos Sinos University (UNISINOS), in São Leopoldo, state of Rio Grande do Sul. In a study published in the scientific journal Zoology in June 2016, Piter Boll, a doctoral researcher advised by Leal-Zanchet, compared the feeding habits of six species of planarians, four from the genus Obama. O. nungara ate more food types: snails, slugs, earthworms, and even other planarians. Theoretically, this worm has the potential to become established in different environments, given the fact that it does not rely on just one kind of food to survive. It inhabits human-modified environments, such as parks, nurseries and gardens.
The fact that there exists a worm genus that bears the name of a president of the United States seems like some sort of joke or insult. USP’s Fernando Carbayo was the person responsible for this bit of drollery, which he himself admits is a spirited artifice intended to call attention to a group of animals that don’t exactly stir up excitement in the general public. But there is a scientific justification for using that designation, which came into being in 2013. That year, Carbayo and other researchers analyzed three regions of nuclear DNA and one mitochondrial DNA marker and subdivided the old genus Geoplana, which included more than 100 neotropical species, into six new genera. One of these was Obama, which currently encompasses 36 species.
Planarians of this genus have a very flattened body, almost as flat as a leaf—a feature that is extremely evident in the species Obama fryi. In the ancient Tupi language, oba means “leaf” and ma means “animal,” hence the justification for the genus name Obama. The term nungara, the name of the planarian species now found also in Europe, comes from Tupi as well and means “similar, resembling.” Thus, Obama nungara was so named because of its resemblance to Obama marmorata, for which it was mistaken until recently, as the Guernsey story illustrates.
Concetrated in the atlantic forest
“That is the official explanation for using the name of a U.S. President for a genus of land planarians. I leave it to you to think whatever you will about the true motivation of those who chose the name. But I think we’re entitled to a little humor…,” was the comment from planarian expert Jean-Louis Justine of the Institute of Systematics, Evolution and Biodiversity of the French National Museum of Natural History, in his blog. It was Justine who discovered the planarian predator from New Guinea in Caen two years ago.
Brazil is considered an important diversity center for land planarians, which usually have nocturnal habits, move around slowly and live in moist environments due to their inability to retain liquids. Of the 900 known species, about 190 are native to Brazil, most of them from the Atlantic Forest. They are normally found in the soil in forests or under tree trunks, rocks or leaves, and hence they are seldom spotted by the untrained eye. At times, there may be dozens of species living in the same area. “I once found 40 different species in just one fragment of araucaria (Brazilian pine) forest in Rio Grande do Sul,” says Leal-Zanchet. “Some of these species were represented by a single specimen.” The few species in the most urbanized area can be mistaken for slugs.
Charles Darwin came across planarians on his famous trip to South America aboard the ship Beagle in the 1830s. In Rio de Janeiro State, he collected an extremely beautiful, colorful specimen in the Atlantic Forest whose body was mostly orange and had two narrow white stripes and one wide black stripe. In 1844, the English naturalist gave this specimen the scientific name Planaria vaginuloides (now changed to Geoplana vaginuloides), based on the animal’s outward appearance and its similarity to slugs of the genus Vaginulus. Since then, different types of planarians with a similar but not identical color pattern have been considered specimens of these species.
Darwin’s planarian subdivided
Carbayo’s team has just completed a taxonomic revision of the species described by Darwin, which exists today only in Pedra Branca State Park, on the west side of the city of Rio de Janeiro. They propose that G. vaginuloides be subdivided into several species. According to Ana Laura Almeida, who presented her master’s thesis on the subject in September 2016, the original species can be separated into more than five new species. “One of them shows a color pattern that is exactly the reverse of G. vaginuloides,” she says. It is black, with two narrow white stripes and one wider orange stripe. Other planarian specimens normally classified as G. vaginuloides also exhibit these colors, but with a different distribution of shades along the body—a peculiarity that Carbayo says is justification for classification as a different species. The USP team has not yet said how many species Darwin’s originally described land worm will be subdivided into, nor can they reveal their new scientific names, because the paper announcing the news has not yet been published.
Taxonomy holds importance for more than just planarian experts. Since global movement of these worms appears to be on the rise, it is also of interest for health surveillance purposes and to those who are tasked with protecting biodiversity to have a close familiarity with the existing types of planarians circulating the globe. According to a science communication article published in the September 2016 issue of the journal American Scientist by planarian expert Ronald Sluys of the University of Leiden in the Netherlands, at least 16 species of these worms can be considered invasive. The case of the snail-eating planarian from New Guinea is the most serious, along with the report of a species from New Zealand (Arthurdendyus triangulatus) that eats earthworms and has also been found in Europe.
The discovery of the Brazilian worm bearing a U.S. president’s name that has reached the Old World is one of the most recent episodes of planarian dispersal. Meanwhile, scientists whose research focuses on Platyhelminthes—the phylum that includes planarians and other worms—appear to be admirers of the White House occupant. In September 2016, a worm that infects Malaysian turtles was named Baracktrema obamai, a double homage to the most powerful man on the planet.
Taxonomic revision of the land planarians of Geoplana (Platyhelminthes, Tricladida) (nº 2014-13661-8); Grant Mechanism Regular Research Grant; Principal Investigator Fernando Carbayo (EACH-USP); Investment R$87,241.45.
CARBAYO, F. et al. The true identity of Obama (Platyhelminthes: Geoplanidae) flatworm spreading across Europe. Zoological Journal of the Linnean Society. V. 117, No. 1, p. 5-28. May 2016.
BOLL, P. K. and LEAL-ZANCHET, A. M. Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest. Zoology. V. 119, No. 3, p. 162-8. June 2016.