Category Archives: worms

Friday Fellow: Brown-gutted Mud Roundworm

by Piter Kehoma Boll

If you have your face buried in the mud at the bottom of a European lake, you may end up finding some of those tiny little roundworms known as Monhystera stagnalis. As usual, there is no common name for this species, but I decided to call it brown-gutted mud roundworm. Why? Because it lives in the mud and has a reddish-brown gut.

monhystera_stagnalis

An individual of Monhystera stagnalis. Photo by Marco Spiller.*

The brown-gutted mud roundworm is a widely distributed roundworm species, being common especially throughout Europe. It inhabits the fine sediments at the bottom of freshwater bodies, both stagnant and flowing, where it feeds on the organic material deposit in this medium, having a special taste for bacteria. It is able to survive in moderate organic pollution, but is sensitive to low oxygen levels.

It is one of the most common nematode species in its environment and it is very small, measuring around 1 mm in length, females being slightly longer than males. They are found in all depths of the sediment and seem to have a preference for staying closer to the surface during winter and deeper in the mud during summer.

Females are ovoviviparous, meaning that they retain the egg inside their bodies until they hatch, so they are pregnant with eggs. Although we are used to think that invertebrates produce hundreds or thousands of eggs at once, this is not the case with the brown-gutted mud roundworm. Females are usually pregnant of a single egg, sometimes with two or three. They are modest worms.

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ResearchBlogging.orgReferences:

Pehofer, H. (1989). Spatial Distribution of the Nematode Fauna and Production of Three Nematodes (Tobrilus gracilis, Monhystera stagnalis, Ethmolaimus pratensis) in the Profundal of Piburger See (Austria, 913 m a.s.l) Internationale Revue der gesamten Hydrobiologie und Hydrographie, 74 (2), 135-168 DOI: 10.1002/iroh.19890740203

Traunspurger, W. (1996). Autecology of Monhystera paludicola De Man, 1880 – Seasonal, Bathymetric and Vertical Distribution of a Free-living Nematode in an Oligotrophic Lake Internationale Revue der gesamten Hydrobiologie und Hydrographie, 81 (2), 199-211 DOI: 10.1002/iroh.19960810205

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Friday Fellow: Persian Carpet Flatworm

ResearchBlogging.orgby Piter Kehoma Boll

A flatworm again, at last! Not a land planarian, but a flatworm nonetheless.

If there is a group of flatworms that may put land planarians in second plan regarding beauty, those are the polyclads. Living in the sea, especially in coral reefs, polyclads are colorful and curly and may be mistaken by sea slugs.

The species I’m introducing here today is Pseudobiceros bedfordi, commonly known as the Persian carpet flatworm or Bedford’s flatworm. It is about 8 cm long and lives in coral reefs along Australia, Indonesia, Philippines and adjacent areas. See how beautiful it is:

A flatworm (Pseudobiceros bedfordi). Raging Horn, Osprey Reef, Coral Sea

The Persian carpet flatworm with its beautiful colors. Photo by Richard Ling.*

The colorful pattern of this and many other polyclad species is likely a warning about their toxicity, although there are few studies regarding toxicity in these animals. Being active predators, polyclads may use their toxins as a way to subdue prey as well.

But the most interesting thing regarding the Persian carpet flatworm is its sexual behavior. As with most flatworms, they are hermaphrodites, so when two individuals meet and decide to have sex, they have to choose whether they want to play the male or the female role (or both). Unfortunately, most individuals prefer to be males, so those encounters usually end up in a violent fight in which both animals attack the partner with a double penis, a behavior known as penis fencing.

mating_pseudobiceros_bedfordi

Two Persian carpet flatworms about to engage in penis fencing. Photo from Whitfield (2004), courtesy of Nico Michiels.**

At the end, the winner spurts its sperm onto the partner and leaves. The horrible part is yet to come, though. The sperm appears to be able to burn like acid through the receiver’s skin tissue in order to reach the inner tissues and thus swim towards the eggs. In some extreme cases the sperm load may be high enough to tore the receiver into pieces! If that’s not a good definition of wild sex, I don’t know what is.

See also: Gender Conflict: Who’s the man in the relationship?

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References:

Whitfield, J. (2004). Everything You Always Wanted to Know about Sexes PLoS Biology, 2 (6) DOI: 10.1371/journal.pbio.0020183

Wikipedia. Pseudoceros bedfordi. Available at: <https://en.wikipedia.org/wiki/Pseudobiceros_bedfordi&gt;. Access on November 24, 2016.

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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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Gender Conflict: Who’s the man in the relationship?

ResearchBlogging.orgby Piter Kehoma Boll

Everyone with some sort of knowledge on evolution have heard of sexual conflict, how males and females have different interests during reproduction, and sexual selection, i.e., how one sex can influence the evolution of the other.

Sexual organisms are almost always defined by the presence of two sexes: male and female. The male sex is the one that produces the smaller gamete (sexual cell) and the female sex is the one that produces the larger gamete. The male gamete is usually produced in large quantities, because as it is small, it is cheaper to produce. On the other hand, the female gamete is produced in small quantities, because its large size makes it an expensive gamete.

A classical image of a male gamete (sperm) reaching a female gamete (egg) during fertilization. See the astonishing difference in size.

A classical image of a male gamete (sperm) reaching a female gamete (egg) during fertilization. See the astonishing difference in size.

As one can clearly see, the female puts a lot more resources in the production of a single descendant than a male does. As a result, females are usually very choosy regarding who will have the honor to fertilize her eggs. Males need to prove that they are worth the paternity, and female choice, through generations, increase male features that they judge attractive. A classical example is the peacock.

The peacock is one of the most famous examples of how sexual selection can drive the evolution of dioecious species. Photo by Oliver Pohlmann.

The peacock is one of the most famous examples of how sexual selection can drive the evolution of dioecious species. Photo by Oliver Pohlmann.

There are a lot of exceptions, of course, most of them driven by the social environment of the species or due to a unusual natural environment which may increase male investment. But all of this stuff refers to dioeicious species, i.e., species in which male and females are separate organisms. But what happens if you are part of a hermaphroditic species, therefore being male and female at the same time? Do you simply mate with anyone? Is everyone versatile everytime they get laid?

Well, there is a lot of diversity in these organism, but all the principles of sexual conflict are still valid. Even if you are male and female at the same time, you still has the desire to fertilize as many eggs as possible with your cheap sperm while choosing carefully who is worth fertilizing your own eggs. The main problem is that anyone else wants the same.

- Come on, darling. Let me fertilize you. - Will you let me fertilize you too? Photo by Jangle1969, Wikimedia user.*

“Come on, darling. Let me fertilize you.”
“Will you let me fertilize you too?”
Photo by Jangle1969, Wikimedia user.*

Imagine that you are a hermaphrodite with a handful of expensive eggs and lots of cheap sperm. You are willing to mate and you go on a hunt. Eventually you find another individual with the same intentions. You look each other in the eyes, get closer and start a conversation. Let’s assume that you didn’t find the other one very attractive to be the father of your children, but you whan to be the father of their children.

“So, what are your preferences?” you ask.
“Right now, I wanna be the male” the other one answers.

“Damn!”, you think. Both of you want the same thing. You guys want to play the same sexual role, so there’s a conflict of interests, or, as it is called, a “gender conflict”. In this case, regarding sexual behavior in biology, the word gender refers to the role you play during sex. Who will be the man in the relationship?

In face of this conflict, this hermaphrodite’s dilemma, you both have to find a solution. There are four possible outcomes:

1. You insist on being the male and your partner agrees to play the female against their will. You win, the other one loses.
2. Your partner insists on being the male and you agree to play the female against your will. The other one wins, you lose.
3. Both of you insist on being the male. Sex doesn’t happen and both of you go home without having got laid.
4. Both of you agree to play both roles. Sex happens and you successully deliver your sperm, but is forced to accept the other guy’s sperm too.

The worst for you is not being able to deliver your sperm, as you wished. So 2 and 3 are the worst outcomes. 1 is the better outcome for you, but how will you convince your partner to be the loser? So, the best solution for everyone is 4. Both are neither fully happy nor fully frustrated.

Eartworms use the 69 position to exchange sperm. Photo by Beentree, Wikimedia user.*

Eartworms use the 69 position to exchange sperm. Photo by Beentree, Wikimedia user.*

But is this the end? Not necessarily. The most stable mating behavior in a population is indeed to agree to play both roles, but things can go on after you kiss your mate goodbye. Now you have to deal with post-copulatory selection.

You have had sex, you delivered your sperm, but received sperm in return. A low-quality sperm in your opinion. You won’t let that fertilize your eggs, will you? Of course not! So, as soon as your partner is out of sight, you simply spit the sperm out before it reaches your eggs! He will never know.

A pair of flatworms, Macrostomum sp., mating. See how the white one, at the end, bends over itself and sucks the other guy's sperm in order to get rid of them. Image extracted from Schärer et al. (2004) [see references].

A pair of flatworms, Macrostomum sp., mating. See how the white one, at the end, bends over itself and sucks the other guy’s sperm out of the female pore in order to get rid of it. Image extracted from Schärer et al. (2004) [see references].

So you cheated your partner! You agreed to receive their sperm in exchange of your own, but then you discarded it as soon as your partner went away. You rule! Right? But… wait! What if they did the same? What if your sperm was discarded too?

You cannot risk that. That would be worse than not having get laid at the first place, because you would have wasted energy and sperm for nothing! But how can you assure that the sperm remains where it is supposed to be?

One strategy is to include some stiff bristles on your sperm cells so that they stick  on the inner wall of the female cavity and cannot be removed. The sperm cells function like thorns or spines that go in easily but are very hard to be pulled back. That’s what some flatworms do.

Two strategies used by species of Macrostomum to force the partner to have your sperm. (A) A species in which two individuals share sperm but later may try to get rid of the partners sperm have evoled sperm cells with bristles that hold the sperm in the female cavity. (B) Other species have evolved a more aggressive behavior, in which they inject sperm in the partner using a sytlet (penis) with a sharp end able to pierce the body. In this case there is no need to have bristled sperm cells. Image extracted from Shärer et al. (2011) [see references].

Two strategies used by species of Macrostomum to force the partner to have your sperm. (A) A species in which two individuals share sperm, but later may try to get rid of the partner’s sperm, have evoled sperm cells with bristles that hold the sperm in the female cavity. (B) Other species have evolved a more aggressive behavior, in which they inject sperm in the partner using a stylet (penis) with a sharp end able to pierce the body. In this case there is no need to have bristled sperm cells.
Image extracted from Shärer et al. (2011) [see references].

Other species evolved a more aggressive approach. They armed their penises with a sharp point that pierces the partners body, forcing it to take the sperm. The sperm is injected in the partner’s tissues and swims towards the eggs.

Both strategies may look like wonderful solutions for the male, but remember that they are hermaphrodites, so that everything can be used against themselves! And that’s the big hermaphrodite’s dilemma, or the ultimate hermaphrodite’s paradox. They are constantly trying to outrun themselves.

Isn’t evolution amazing?

See also: Endosperm: the pivot of the sexual conflict in flowering plants.

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References and futher reading:

Anthes, N., Putz, A., & Michiels, N. (2006). Hermaphrodite sex role preferences: the role of partner body size, mating history and female fitness in the sea slug Chelidonura sandrana Behavioral Ecology and Sociobiology, 60 (3), 359-367 DOI: 10.1007/s00265-006-0173-5

Janicke, T., Marie-Orleach, L., De Mulder, K., Berezikov, E., Ladurner, P., Vizoso, D., & Schärer, L. (2013). SEX ALLOCATION ADJUSTMENT TO MATING GROUP SIZE IN A SIMULTANEOUS HERMAPHRODITE Evolution, 67 (11), 3233-3242 DOI: 10.1111/evo.12189

Leonard, J. (1990). The Hermaphrodite’s Dilemma Journal of Theoretical Biology, 147 (3), 361-371 DOI: 10.1016/S0022-5193(05)80493-X

Leonard, J., & Lukowiak, K. (1991). Sex and the simultaneous hermaphrodite: testing models of male-female conflict in a sea slug, Navanax intermis (Opisthobranchia) Animal Behaviour, 41 (2), 255-266 DOI: 10.1016/S0003-3472(05)80477-4

Marie-Orleach, L., Janicke, T., & Schärer, L. (2013). Effects of mating status on copulatory and postcopulatory behaviour in a simultaneous hermaphrodite Animal Behaviour, 85 (2), 453-461 DOI: 10.1016/j.anbehav.2012.12.007

Schärer, L., Joss, G., & Sandner, P. (2004). Mating behaviour of the marine turbellarian Macrostomum sp.: these worms suck Marine Biology, 145 (2) DOI: 10.1007/s00227-004-1314-x

Schärer, L., Littlewood, D., Waeschenbach, A., Yoshida, W., & Vizoso, D. (2011). Mating behavior and the evolution of sperm design Proceedings of the National Academy of Sciences, 108 (4), 1490-1495 DOI: 10.1073/pnas.1013892108

Schärer, L., Janicke, T., & Ramm, S. (2015). Sexual Conflict in Hermaphrodites Cold Spring Harbor Perspectives in Biology, 7 (1) DOI: 10.1101/cshperspect.a017673

Wethington, A., & Dillon, JR, R. (1996). Gender choice and gender conflict in a non-reciprocally mating simultaneous hermaphrodite, the freshwater snail,Physa Animal Behaviour, 51 (5), 1107-1118 DOI: 10.1006/anbe.1996.0112

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The fabulous taxonomic adventure of the genus Geoplana

by Piter Kehoma Boll
ResearchBlogging.org

Freshwater planarians are relatively well-known as those cute arrow-shaped cockeyed animals. Land planarians are far away from having all the fame of their aquatic cousins and most people do not even know that they exist. Maybe in part it is because deeper studies of the natural world began in Europe, a continent were land planarians are almost non-existent. The first of those little animals to be known was described in 1774 by the Danish naturalist Otto Friedrich Müller. He named the small worm Fasciola terrestris, because he thought it was a terrestrial version of the parasitic worm. It was a small cyllindrical worm with a dark back and two small eyes at the anterior region.

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In 1788, the naturalist Johann Friedrich Gmelin transfered the species to the genus Planaria, described in 1776 by Müller. The worm was, therefore, now called Planaria terrestris. The genus, at this time, included everything that is currently known as planarian: worms with a ventrally located mouth, close to the middle part of the bod. The term most likely became popular by this time and so it continues until today as a general name for these animals.

planaria_terrestris

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Planarians with many eyes were transfered in 1831 by the naturalist Christian Gottfried Ehrenberg to a new genus, Polycelis. The term means “many dots” and refers to the dark dots that the eyes represent on the body.

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During Charles Darwin’s voyage around the world aboard the Beagle, he spent some time in the Brazilian Atlantic Forest and found several species of land planarians. He classified them in the genus Planaria, but highlighted that they formed a section within the genus because of their terrestrial habits, convex bodies and often colorful stripes. The first new species listed by him was called Planaria vaginuloides and was collected in the forests of Rio de Janeiro. The epithet vaginuloides was chosen because Darwin found them to be similar to slugs of the genus Vaginulus.

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One year later, in 1845, the naturalist Émil Blanchard found a species in Chile and named it Polycladus gayi. The name of the genus, Polycladus, refers to the highly branched gut of these animals, while the epithet gayi honors the naturalist Claudio Gay. But Blanchard made a terrible mistake: he mistook the anterior end for the posterior end and so thought that the genital opening was in front of the mouth!

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In 1850, the naturalist Karl Moriz Diesing transferred Darwin’s land planarians to the genus Polycelis because they have many eyes. Planaria vaginuloides was now Polycelis vaginuloides.

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In 18851, the zoologist Joseph Leidy found another land planarian species in Europe that was also small, cylindrical and with two eyes. He named it Rhynchodemus sylvaticus. The term Rhynchodemus means something like “bill-shaped body”. He also suggested the transference of Planaria terrestris to the new genus, so that it was now Rhynchodemus terrestris. Darwin and Blanchard’s species remained as Polycelis and Polycladus.

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Then in 1857 something funny happened. A new revision of land planarians was done by William Stimpson. He, for the first time, separated land planarians from freshwater ones and divided them in two families:

  1. Polycladidae: having a single genus, Polycladus, because it was still thought, at this time, that the genital opening was before the mouth.
  2. Geoplanidae: the rest of land planarians. Species in this family were divided into three genera:
  • Rhynchodemus: species with two eyes;
  • Bipalium: a genus for recently discovered species that have a hammer- or crescent-shaped head. The name comes from Latin bi-, two and pala, shovel.
  • Geoplana: species with many eyes. The name comes from geo, earth, and plana, flat, because of the flat body of those animals, as well as a direct reference to the genus Planaria, now restricted to aquatic species. The species Polycelis vaginuloides became Geoplana vaginuloides. So we arrive to the central genus of this story.
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By a huge coincidence, in this very same year of 1857, the naturalist Max Schultze, based on information from literature and new species collected in Brazil by the naturalist Fritz Müller, also decided to separate land planarians into another genus and also chose the name Geoplana! What are the chances? The papers of Stimpson and Schultze had only some weeks between them and everything seems to indicate that Schultze was unaware of Stimpson’s paper. The main difference between both papers is that Schultze ignored the discovery of the species classified as Bipalium. He also transfered all land planarians to Geoplana, so that Polycladus gayi, Rhynchodemus sylvaticus and Rhynchodemus terrestris were now Geoplana gayi, Geoplana sylvatica and Geoplana terrestris.

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Stimpson’s system, however, prevailed, and the four genera remained in use: Rhynchodemus, Bipalium, Geoplana and Polycladus. Among the species described by Schultze and Müller was Geoplana subterranea, an albine and eyeless species found underground and that feeds on earthworms. In 1861, Diesing decided to put this species into its own genus, Geobia. We had now 5 genera: Rhynchodemus, Bipalium, Geoplana, Geobia and Polycladus.

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In 1877, Henry Nottidge Moseley described a series of species from Australia, the Pacific and southeast Asia. A good amount of them were included in the genus Geoplana, but some of them were put in two new genera:

  1. Dolichoplana (“long flat”): very long and narrow species with two eyes as in Rhynchodemus;
  2. Caenoplana (“recent flat”): species considered by him to be intermediate between Geoplana and Dolichoplana because the body was longer and the eyes were restricted to the sides of the body.
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Ten years later, in 1887, J. J. Fletcher and A. G. Hamilton studied Australian land planarians and concluded that there was no need for the species named Caenoplana by MOseley to be in a separate genus and united them to Geoplana.

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During the following decade, the naturalist Arthur Dendy described several new species from Australia and New Zealand, classifying all in the genus Geoplana. The genus was growing, having tenths of species. In the last years of the 19th century, several new genera were created, many of them in the works of the zoologist Ludwig von Graff. These new genera were erected to species with very peculiar anatomical features, such as a differentiated head, for example. Anyway, the genus Geoplana kept growing. Any flat and many-eyed land planarian without a distinct feature was thrown into this genus. This system continued throughout most of the 20th century. Tenths of new species were described by the zoologist Libbie Hyman and by two zoologist couples: the Marcuses – Ernst Marcus and Eveline du Bois-Reymond Marcus – and the Froehlichs — Claudio Gilberto Froehlich and Eudóxia Maria Froehlich. These new species were mostly put in Geoplana. At that time the genus was widely distributed in South America and Australia.

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During this time, E. M. Froehlich determined that Geoplana vaginuloides should be the type species of the genus Geoplana. Perhaps you are now asking yourself “what is a type species?”. Well, in taxonomy, when a new genus is created, one of its species has to be considered the type species, the species that serves as a “model” to the genus. It is the type species that defines what the genus is. Once a species becomes the type species of the genus, it can never pass to another genus, except if the entire genus ceases to exist. Afterall, it is the species in which the existence of the genus is based. The fact is that in the 18th and 19th centuries there was no policy of type species, which was only later introduced in the rules to give names to organisms. Therefore Stimpson, when he created the genus Geoplana, did not define a type speciees. E. M. Froehlich chose Geoplana vaginuloides as the type-species because it was the first species listed by Stimpson and the proposal was accepted by the scientific community.

Let’s go back to the main subject. As it was said, the genus Geoplana was gathering more and more species throughout the 20th century, becoming huge. Then in 1990 the zoologists Robert Ogren and Masaharu Kawakatsu decided to clean the mess. By examining the inner anatomy of land planarians, they excluded from Geoplana all species from Australia and nearby areas because they have testes placed in the ventral region of the body, diferently from South American species, that have them in the dorsal region. However, letting all the South American pack inside Geoplana would still be a mess. So, they broke the genus into several smaller genera. The four main genera were defined based on two features of the copulatory apparatus: 1) the presence or absence of a penis papilla, i.e., a penis. Some planarians have a penis and some don’t. 2) The position of the oviducts, i.e., the canals that carry the eggs from the ovaries to a cavity named female atrium. The oviducts may enter the female atrium at the dorsal side or the ventral side. The classification of this two features allows four combinations:

  1. Species with a penis papilla and with oviducts entering dorsally. These species continued in the genus Geoplana, because this is the combination that occurs in Geoplana vaginuloides.
  2. Species with a penis papilla and with oviducts entering ventrally. These species passed to the genus Gigantea.
  3. Species without a penis papilla and with oviducts entering dorsally. These species were named Notogynaphallia.
  4. Species without a penis panilla and with oviducts entering ventrally. This is the opposite of what is found in Geoplana. These species were transfered to a genus named Pasipha.
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Things were starting to get more organized. Despite still having more than a hundred species, the genus Geoplana was a little more homogeneous now. But by the beginning of the 21th century, more detailed studies on the internal anatomy of planarians demonstrated that other parts of the body also had taxonomic importance. Furthermore, molecular studies were now available and the genus was challenged by the molecular phylogeny. The already expected result was confirmed. A study of molecular phylogeny by Fernando Carbayo and colleagues in 2013 revealed that the genus Geoplana, as defined by Ogren and Kawakatsu, was still a mess. Species were separated in several groups that needed to received their own genera. These new genera created from Geoplana were: Barreirana, Cratera, Matuxia, Obama and Paraba.

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At the end the type species, Geoplana vaginuloides, remained almost alone. The only other species that grouped with it was Geoplana chita. The genus Geoplana, once with hundreds of species throughout the whole world, now has only two species restriced to the Atlantic Forest between the Brazilian states of Rio de Janeiro and Paraná. And guess which of the new genera received most of the species one in Geoplana?

 

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Yes, we can!

Yes, we can!

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References:

Carbayo, F., Álvarez-Presas, M., Olivares, C., Marques, F., Froehlich, E., & Riutort, M. (2013). Molecular phylogeny of Geoplaninae (Platyhelminthes) challenges current classification: proposal of taxonomic actions Zoologica Scripta, 42 (5), 508-528 DOI: 10.1111/zsc.12019

Darwin, C. 1844. Brief description of several terrestrial planariae, and of some remarkable marine species, with an account of their habits. Annals and Magazine of Natural History, Annales de Sciences Naturelles, 14: 241-251.

Diesing. K. M. 1850. Systema helminthum. Academia Caesareae Scientiarium.

Fletcher, J. J.; Hamilton, A. G. 1887. Notes on Australian land-planarians, with descriptions of some new species. Part I. Proceedings of the Linnean Society of New South Wales, 2: 349-374.

Froehlich, E. M. 1955. Sôbre espécies brasileiras do gênero GeoplanaBoletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Série Zoologia, 19: 289-339.

Gay, Claudio. 1849. Historia fisica y politica de Chile. Vol. 3.

Gmelin, O. F. 1788. Systema Naturae. Moseley, H. N. 1877. Notes on the structure of several forms of land planarians with a description of two new genera and several new species, and a list of all species at present known. Quarterly Journal of Microscopical Sciences, 17: 274-292.

Ogren, R.; Kawakatsu, M. 1990. Index to the species of the family Geoplanidae (Turbellaria, Tricladida, Terricola) Part I: Geoplaninae. Bulletin of Fuji Women’s College, 28: 79-166.

Schultze, M.; Müller, F. 1857. Beiträge zur Kenntnis der Landplanarien. Abhandlungen der Naturforschenden Gesellschaft zu Halle, 4: 61-74.

Stimpson, W. 1857. Prodromus descriptionis animalium evertebratorum quae in expeditione ad Oceanum, Pacificum Septentrionalem a Republica Federata missa Johanne Rodgers Duce, observavit et descripsit. Pars I. Turbellaria Dendrocoela. Proceedings of the Academy of Natural Sciences of Philadelphia, 19-31.

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Friday Fellow: Heartworm

by Piter Kehoma Boll

Life is not composed only by beautiful and cute creatures. Parasites form a big part of life. In fact, it is likely that there are more parasitic species than non-parasitic ones.

The heartworm (Dirofilaria immitis) is one of these not-so-cute species. A species of roundworm, it infects small mammals, especially dogs, and is spread by mosquitoes.

The name heartworm comes from the fact that this worm lives in the heart and pulmonary arteries of dogs during its adult stage. The result of the infection may be heart failure and damage on the heart and the arteries, but some infections may pass completely unnoticed, especially in sedentary dogs.

Not a pleasant view. Heartworms in a dog's heart. Photo by Alan R Walker*.

Not a pleasant view. Heartworms in a dog’s heart. Photo by Alan R Walker*.

After males and females mate in the heart of the dog, females give birth to live larvae called microfilariae. These are released in the bloodstream and await for being transfered to a bloodsucking mosquito during a bite. Over 60 species of mosquitoes are known to serve as intermediate hosts of microfilariae.

Inside the mosquito, the microfilariae grow from the larval stage L1 to the larval stage L3 and then migrate to the mosquito’s salivary glands and, once it bites another dog, they are transferred to it and develop under the skin at the site of the bite to the stage L4. Now the L4 larve migrate to the dog’s muscles and develop into the stage L5. Finally, they start to migrate through the bloodstream until they reach the heart and the pulmonary artery, where they mold into adults and the cycle is complete.

We may find such worms disgusting, but we must admit that they have a complex and amazing life.

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References:

Wikimedia. Dirofilaria immitis. Available at: < https://en.wikipedia.org/wiki/Dirofilaria_immitis >. Access on June 7, 2012.

Ludlam, K. W.; Jachowski, L. A.; Otto, G. G. 1970. Potential vectors of Dirofilaria imiitis. Journal of the American Veterinary Medical Association, 157: 1354-1359.

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Filed under Friday Fellow, Parasites, worms