Tag Archives: invasive species

Friday Fellow: Giant Salvinia

by Piter Kehoma Boll

We are moving out of the sea this week, but will still remain in the water to bring you a peculiar fern. Commonly known as giant salvinia, kariba weed or giant watermoss, its scientific name is Salvinia molesta and it comes from southeastern Brazil.

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Fronds of Salvinia molesta growing in Hawaii. Photo by Forrest & Kim Starr.*

The water salvinia is an aquatic fern that floats on the surface of the water and has a peculiar anatomy. It lacks roots, and it produces leaves in sets of three. Two of them remain at the surface of the water, side by side, and the third one is submerged, acting like a modified root. The upper side of the surface leaves (which are anatomically their underside) have many small hairs that turn them into a waterproof surface and the underside have very long hairs that look like roots.

Preferring slow-moving waters, the giant salvinia grows very quickly in ideal conditions and has become an invasive species in several parts of the world. It was exported from Brazil to be used in aquaria and garden ponds and ended up in natural environments. While spreading, the giant salvinia can cover the entire surface of water bodies, blocking light for other plants and algae, which decreases photosynthesis and reduces the amount of oxygen in the water. Additionally, it can clog waterways, blocking natural or artificial water flows.

The problem caused by the giant salvinia in areas where it has become invasive led to the development of control methods. One of the simplest methods is simply removing the plants mechanically, but it is difficult in areas with large infestations, as even small remaining populations may quickly recover. Another alternative is the use of biological control using Cyrtobagous salviniae, a tiny weevil that feeds on the giant salvinia in its natural environment.

Not everything about the giant salvinia is bad, actually. Its peculiar leaf anatomy led to the discovery of what was properly called “the salvinia effect”, a phenomen by which an air layer becomes stable over a submerged surface, as in the leaves of species of Salvinia. By developing artificial structures that make use of this phenomenon, it is possible to produce devices that move smoothly in water, such as ships with reduced friction.

A considerably recent study also found out that some compounds extracted from the giant salvinia are effective in the control of human tumor cells.

Our relationship with this peculiar plant is therefore one of love and hate.

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References:

Coetzee, J. A.; Hill, M. P.; Byrne, M. J.; Bownes, A. (2011) A Review of the Biological Control Programmes on Eichhornia crassipes (C.Mart.) Solms (Pontederiaceae), Salvinia molesta D.S.Mitch. (Salviniaceae), Pistia stratiotes L. (Araceae), Myriophyllum aquaticum (Vell.) Verdc. (Haloragaceae) and Azolla filiculoides Lam. (Azollaceae) in South Africa. African Entomology 19: 451-468.

Li, S.; Wang, P.; Deng, G.;  Yuan, W.; Su, Z. (2013)  Cytotoxic compounds from invasive giant salvinia (Salvinia molesta) against human tumor cells. Bioorganic & Medicinal Chemistry Letters 23(24): 6682-6687.

Wikipedia. Salvinia molesta. Available at < https://en.wikipedia.org/wiki/Salvinia_molesta >. Access on February 21, 2018.

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Hundreds of lionfish were released in the Atlantic out of pity

by Piter Kehoma Boll

The red lionfish, Pterois volitans, is a beautiful and venomou coral fish native from the Indo-Pacific region. Due to its great beauty, it is a very popular in fish tanks all around the world.

799px-red_lionfish_near_gilli_banta_island

A red lionfish in its natural and native habitat in Indonesia. Photo by Alexander Vasenin.*

Since the 1980s, the lionfish started to be found in the waters of the Atlantic ocean around Florida. How did they get there? Certainly humans had something to do with it, but the exact way is yet unknow. Originally a small population, the species spread quickly by the beginning of the 21th century and in 2010 had colonized the Caribbean and the Gulf of Mexico.

Some original studies on the genetic diversity of the Atlantic population estimated that the minimum number of introduced specimens was around 10. If that was true, the established population may have been the result of an accident, like, for example, the fish of a single aquarium accidentally ending up in the sea.

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A red lionfish photographed in Curaçao, Caribbean. Photo by Laszlo Ilyes.**

A recently published study (see reference), however, reestimated this number using new models and additional data. The conclusions are that the number of fish that colonized the Atlantic was much bigger, around 272 individuals. Such a large introduction would unlikely occur by accident. Introductions by fish being transported from the Indo-Pacific region in the ballast water of ships is unlikely, as they would hardly survive the transport. The most likely answer is that these fish were introduced through several small releases that happened in Miami. How and why? Well, many people like to have fish in beautiful fish tanks at home, and when they get tired of managing the animals or cannot afford continuing to have them, they decide to simply release them in the ocean out of pity, because the alternative would be to kill them.

Now can you see what are the consequences of thinking this way? You care too much for a single specimen, has no ecological knowledge, and simply decide to release them in the wild. Years later, they have depleted whole ecosystems and caused a large-scale disaster. That’s what humans do. As they say, the road to hell is paved with good intentions.

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References:

Selwyn JD, Johnson JE, Downey-Wall AM, Bynum AM, Hamner RM, Hogan JD, Bird CE. (2017Simulations indicate that scores of lionfish (Pterois volitans) colonized the Atlantic OceanPeerJ 5:e3996 https://doi.org/10.7717/peerj.3996

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Friday Fellow: Brown Mussel

by Piter Kehoma Boll

Until now, the mollusks featured here included a chiton, a cephalopod and two gastropods. So it is time to bring a bivalve. And what would be better than showing you a common mollusk from the South Atlantic Ocean?

Living on rocky shores around South America and Africa, our fellow is called Perna perna, or populary brown mussel. In places where it lives, it can be found in great concentrations, sometimes covering large areas of rocks. It usually measures about 90 mm in length, but some larger specimens may reach up to 120 mm. The increased surface area on the rocks they occupy attract other rock-living marine species, such as barnacles, limpets, snails and algae.

Perna_perna

Some specimens of Perna perna growing on an oyster in South Africa. Photo by Bernadette Hubbart.*

The brown mussel is a filter feeder, as most bivalves, feeding on suspended organic matter, as well as on small microrganisms, such as phytoplankton and zooplankton. As a prey, it is eaten by a variety of animals, such as sea birds, crustaceans and mollusks. Humans also consume it in both South America and Africa. Its ingestion, however, must be cautious, as it may contain toxins from dinoflagellates that it ingested, as well as heavy metals from water pollutants.

Spread through the world by humans after attaching itself on ships, the brown mussel has become invasive in other parts, especially in the Gulf of Mexico, and it continues to increase its occupied area. This can have deleterious effects both ecologically and economically, as it may displace native species and also cause damage to human equipments. It is, therefore, one more species that became a problem due to us, humans. And the damage will not be easy to be repared.

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References:

Ferreira, A. G.; Machado, A. L. S.; Zalmon, I. R. (2004) Temporal and spatial variation on heavy metal concentrations in the bivalve Perna perna (LINNAEUS, 1758) on the northern coast of Rio de Janeiro State, Brazil. Brazilian Archives of Biology and Technology 47(2): 319–327. http://dx.doi.org/10.1590/S1516-89132004000200020

Holland, B. S. (2001) Invasion without a bottleneck: microsatellite variation in natural and invasive populations of the brown mussel Perna perna (L). Marine Biotechnology 3, 407–415. https://dx.doi.org/10.1007/s1012601-0060-Z

Wikipedia. Perna perna. Available at: < https://en.wikipedia.org/wiki/Perna_perna >. Access on October 21, 2017.

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Going a long way with your mouth open to new tastes

by Piter Kehoma Boll

Everybody knows that human activities have driven our environment toward an unfortunate situation. The most popular forms of human impact include pollution, deforestation and overexploitation of natural resources, but certainly an important factor in remodeling ecosystems is the invasion of species.

While humans move around the world, they carry many species with them, either intentionally or not, an some of them establish successfully in the new environment, while others do not. But what makes some species become successful invaders while other are unable to do so?

It is clear for some time that having a broad niche, i.e., a broad tolerance in environmental conditions and a broad use of resources is very important to succeed in invading a new habitat. Food niche breadth, i.e., the amount of different food types one can ingest, is among the most important dimensions of the niche influencing the spread of a species.

I myself studied the food niche breadth of six Neotropical land planarians in my master’s thesis (see references below) and it was clear that the species with the broader niche are more likely to become invasive. Actually, the one with the broadest food niche, Obama nungara, is already an invader in Europe, as I already discussed here.

obama_marmorata_7

A specimen of Obama nungara from Southern Brazil that I used in my research. Photo by myself, Piter Kehoma Boll.*

But O. nungara has a broad food niche in its native range, which includes southern Brazil, and likely reflected this breadth in Europe. But could a species that has a narrow food niche in its native range broaden it in a new environment?

A recent study by Courant et al. (see references) investigated the diet of the African clawed frog, Xenopus laevis, that is an invasive species in many parts of the world. They compared its diet in its native range in South Africa whith that in several populations in other countries (United States, Wales, Chile, Portugal and France).

Xenopus_laevis

The African clawed frog Xenopus laevis. Photo by Brian Gratwicke.**

The results indicated that X. laevis has a considerable broad niche in both its native and non-native ranges, but the diet in Portugal showed a greater shift compared to that in other areas, which indicates a great ability to adapt to new situations. In fact, the population from Portugal lives in running water, while in all other places this species prefers still water.

We can conclude that part of the success of the African clawed frog when invading new habitats is linked to its ability to try new tastes, broadening its food niche beyond that from its original populations. The situation in Portugal, including a different environment and a different diet, may also be the result of an increased selective pressure and perhaps the chances are that this population will change into a new species sooner than the others.

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References:
Boll PK & Leal-Zanchet AM (2016). Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest. Zoology 119: 162–168.

Courant J, Vogt S, Marques R, Measey J, Secondi J, Rebelo R, Villiers AD, Ihlow F, Busschere CD, Backeljau T, Rödder D, & Herrel A (2017). Are invasive populations characterized by a broader diet than native populations? PeerJ 5: e3250.

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Obama invades Europe: “Yes, we can!”

ResearchBlogging.orgby Piter Kehoma Boll

This information was known by me and some other people for quite a while, but only recently has caught attention of the general public. Obama is the newest threat in Europe.

No, I’m not talking about the president of the United States. I’m talking about a land flatworm whose name is  Obama nungara.

obama_marmorata_7

This is the magnificent Obama nungara. This specimen is from Brazil and looks particulary yellowish due to the strong light of the camera flash. Photo by Piter Kehoma Boll.*

It has been a while since a new invasive land flatworm started to appear in gardens of Europe, especially in Spain and France and eventually elsewhere, such as in the United Kingdom. It was quickly identified as being a Neotropical land planarian and posteriorly as belonging to the genus Obama, whose name has nothing to do with Barack Obama, but is rather a combination of the Tupi words oba (leaf) and ma (animal) as a reference to the worm’s shape.

obama_nungara

When you find Obama nungara in your garden, it will look much darker, like this one found in the UK. Photo by buglife.org.uk

At first it was thought that the planarian belonged to the species Obama marmorata, a species that is native from southern Brazil, but molecular and morphological analyses revealed it to be a new species. Actually, much of what was called Obama marmorata in Brazil was this new species. Thus, it was named nungara, which means “similar” in Tupi, due to its similarity with Obama marmorata.

obama_marmorata

This is Obama marmorata, the species that O. nungara was originally mistaken for. Photo by Fernando Carbayo.**

Measuring about 5 cm in length, sometimes a little more or a little less, O. nungara is currently known to feed on earthworms, snails, slugs and even other land planarians. Its impact on the European fauna is, however, still unknown, but the British charitable organization Buglife decided to spread an alert and many news websites seem to have loved the flatworm’s name and suddenly a flatworm is becoming famous.

Who said flatworms cannot be under the spotlight? Yes, they can!

See also: The Ladislau’s flatworm, a cousin of Obama nungara.

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References:

Álvarez-Presas, M., Mateos, E., Tudó, À., Jones, H., & Riutort, M. (2014). Diversity of introduced terrestrial flatworms in the Iberian Peninsula: a cautionary tale PeerJ, 2 DOI: 10.7717/peerj.430

Boll, P., & Leal-Zanchet, A. (2016). Preference for different prey allows the coexistence of several land planarians in areas of the Atlantic Forest Zoology, 119 (3), 162-168 DOI: 10.1016/j.zool.2016.04.002

Carbayo, F., Álvarez-Presas, M., Jones, H., & Riutort, M. (2016). The true identity of Obama (Platyhelminthes: Geoplanidae) flatworm spreading across Europe Zoological Journal of the Linnean Society, 177 (1), 5-28 DOI: 10.1111/zoj.12358

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Biological fight: Should we bring mammoths back?

by Piter Kehoma Boll

Everybody knows the amazing large animals that are found in Africa and Southeast Asia. Elephants, giraffes, rhinos, hippos, horses, lions, tigers… such large creatures, mostly mammals, are usually called megafauna, the “large fauna”.

Mammals as big as the African bush elephant once roamed the Americas. Photo by flickr user nickmandel2006*.

Mammals as big as the African bush elephant once roamed the Americas. Photo by flickr user nickmandel2006*.

The Americas once had an astonishing megafauna too, full of mastodons, mammoths, giant sloths, giant armadillos and sabertooth tigers. Nowadays it is restricted to some bears and jaguars. What happened to the rest of them? Well, most went extinct at the end of the Pleistocene, around 11,ooo years ago.

South America once had mammals as big as an African bush elephant. Picture by Dmitry Bogdanov** (dibgd.deviantart.com)

South America once had mammals as big as an African bush elephant, such as the giant sloth. Picture by Dmitry Bogdanov** (dibgd.deviantart.com)

As humans already inhabited the Americas by this time, it was always speculated if humans had something to do with their extinction. It is true that nowadays hundreds, thousands of species are endangered due to human activities, so it is easy to think that humans are the best explanation for their extinction, but 10 thousands years ago the number of humans on the planet was thousands of times smaller than today and our technology was still very primitive, so it is unlikely that we could hunt a species to extinction by that period… if we were working alone.

No, I’m not talking about humans cooperating with aliens! Our sidekick was the famous climate change. Periods of extreme warming during the pleistocene seem to have had a strong impact on the populations of many large mammals and, with the aid of humans hunting them down and spreading like an invasive species, the poor giants perished.

Le Mammouth by Paul Jamin

Le Mammouth by Paul Jamin

This happened more than 10 thousand years ago, TEN THOUSAND YEARS.

In Africa, elephants and large carnivores are well known for their importance in structuring communities, especially due to their trophic interactions that shape other populations. The extinct American megafauna most likely had the same impact on the ecosystem. As a result, suggestions to restore this extinct megafauna has been proposed, either by cloning some of the extinct species or, more plausibly, by introduced extant species with a similar ecological role.

Svenning et al. (2015) review the subject and argue in favor of the reintroduction of megafauna to restore ecological roles lost in the Pleistocene, an idea called “Pleistocene rewilding” or “trophic rewilding”, as they prefer. They present some maps showing the current distribution of large mammals and their historical distribution in the Pleistocene, which they call “natural”. They also propose some species to be introduced to substitute the ones extinct, including replacements for species extinct as long as 30 thousand years ago. Now is this a good idea? They think it is and one of the examples used is the reintroduction of wolves in the Yellowstone National Park. But wolves were not extinct for millenia there, neither are they a different species that would replace the role of an extinct one.

A wolf pack in Yellowstone National Park

A wolf pack in Yellowstone National Park

Rubenstein & Rubenstein (2016) criticized the idea, arguing that we should focus on protecting the remaining ecosystems and not trying to restore those that were corrupted thousands of years ago. They also argue that using similar species may have unintended consequences. Svenning et al. answered that this is mere opinion and that a systematic research program on trophic rewilding should be developed. The reintroduction of horses in the New World and its non-catastrophic consequences is another point used to respond to the critiques.

So what’s your opinion? Should we bring mammoths, mastodonts, giant sloths and sabertooth tigers back? Should we introduce elephants and lions in the Americas to play the role that mastodonts and smilodonts had?

My opinion is no. The idea may seem beautiful, but I think it is actually fantastic, too fabulous and sensational. Horses may have come back to the Americas without bringing destruction, but we cannot be sure with anything, even with several theoretical and small-scale studies. We all know how often introducing species goes wrong, very wrong. Look at poor Australia and Hawaii, for instance. Furthermore, those giant mammals went extinct TEN THOUSAND YEARS AGO. Certainly ecosystems have adapted to their extinction. Life always finds a way. There are worse threats to those ecosystems to be addressed, such as their eminent destruction to build more cities and raise more cattle and crops.

Get over it. Mammoths are gone. Let’s try to save the elephants instead, but without bringing them to the Brazilian cerrado. They don’t belong there. They belong in the African savannah.

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References:

Rubenstein, D. R.; Rubenstein, D. I. From Pleistocene to trophic rewilding: A wolf in sheep’s clothing. PNAS, 113(1): E1. DOI: 10.1073/pnas.1521757113

Svenning, J-C.; Pedersen, P. B. M.; Donlan, C. J.; Ejrnæs, R.; Faurby, S.; Galetti, M.; Hansen, D. M.; Sandel, B.; Sandom, C. J.; Terborgh, J. W.; Vera, F. W. M. 2016. Science for a wilder Anthropocene: Synthesis and future directions for trophic rewilding research. PNAS, 113(4): 898-906. DOI: 10.1073/pnas.150255611

Svenning, J-C.; Pedersen, P. B. M.; Donlan, C. J.; Ejrnæs, R.; Faurby, S.; Galetti, M.; Hansen, D. M.; Sandel, B.; Sandom, C. J.; Terborgh, J. W.; Vera, F. W. M. 2016. Time to move on from ideological debates on rewilding. PNAS, 113(1): E2-E3. DOI: 10.1073/pnas.1521891113

Wade, L. 2016. Giant jaguars, colossal bears done in by deadly combo of humans and heat. Science News. DOI: 10.1126/science.aag0623

Wade, L. 2016. Humans spread through South America like an invasive species. Science News. DOI: 10.1126/science.aaf9881

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Friday Fellow: ‘Orange Jaguar Snail’

by Piter Kehoma Boll

ResearchBlogging.orgLast week I introduced a land planarian that feeds on land snails, Obama ladislavii, or, as I called it, the Ladislau’s flatworm. Therefore, today, I thought it would be great to present a similar situation occurring backwards: a land snail that feeds on land planarians.

So let me introduce this little predator, the land snail Rectartemon depressus. Again, it is not a widely known species and thus it has no common names, but why not call it the ‘orange jaguar snail’? Species of the genus Euglandina, which are also predatory snails, are called ‘wolf snails’ by comparing them to a common predator in North America. As Rectartemon species are common in South America, we could perfectly call them ‘jaguar snails’, right?

Rectartemon depressus about to capture a land planarian Obama marmorata. Photo from Lemos et al., 2012

Rectartemon depressus about to capture a land planarian Obama marmorata. Photo extracted from Lemos et al., 2012

Found in areas of Atlantic Rainforest in Brazil, the orange jaguar snail has a yellow to orange body and a whitish shell. It is listed a vulnerable species in the Brazilian Red List, but it is not mentioned in the IUCN’s Red List.

Initially known as a predator of other land gastropods, the orange jaguar snail revealed a new item in its diet recently. During attempts to find the food items in the diet of some land planarians from southern Brazil, the orange jaguar snail was offered as a food option, but while the expectations were that the planarian would eat the snail, the opposite happened! After contacting the land planarian, the snail simply grasps it with its radula (the snail’s toothed tongue) and sucks it in very quickly, just as if it were eating a noodle!

The orange jaguar snail eagerly consumes several land planarians, both native and exotic species. It makes it one of the first known predators of land planarians. One of its prey is the Ladislau’s flatworm, so we have a snail that eats a flatworm that eats snails!

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References:

Lemos, V., Canello, R., & Leal-Zanchet, A. 2012. Carnivore mollusks as natural enemies of invasive land flatworms. Annals of Applied Biology, 161 (2), 127-131 DOI: 10.1111/j.1744-7348.2012.00556.x

Santos, S. B., Miyahira, I. C., Mansur, M. C. D. 2013. Freshwater and terrestrial molluscs in Brasil: current status of knowledge and conservation. Tentacle, 21, 40-42.

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