Friday Fellow: Flat-Leaved Scalewort

by Piter Kehoma Boll

Time and again, if we want to understand all the nuances of life on Earth, we have to look to the small things that live close to the ground or on the bark of the trees. And one of this small creatures is the flat-leaved scalewort, Radula complanata.

Growing on rocks or trees, the flat-leaved scalewort is quite common in the northern hemisphere, especially in North America and Eurasia, and belongs to the diverse but hidden group of the liverworts.

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Radula complanata growing on the trunk of an ash tree (Fraxinus excelsior) in England. Credits to BioImages – the Virtual Fieldguide (UK).*

In Europe, the flat-leaved scalewort occurs in dense forests, where it finds shelter to the direct exposure to the sun. In this forests, it shows a clear preference for growing on broad-leaved trees and shrubs, such as the goat willow Salix caprea and its hybrids. It usually grows friendly with other epiphytic liverworts on the same tree, although not much clustered.

Although usually harmless, the flat-leaved scalewort can cause skin irritation (more precisely, allergenic contact dermatitis) when handled, which seems to be related to the presence of certain alcaloids, such as bibenzyls, in its tissues.

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References:

Asakawa, Y.; Kusube, E.; Takemoto, T.; Suire, C. (1978) New Bibenzyls from Radula complanataPhytochemistry, 17: 2115–2117. https://dx.doi.org/10.1016/S0031-9422(00)89292-4

Heylen, O.; Hermy, M. (2008) Age structure and Ecological Characteristics of Some Epiphytic Liverworts (Frullania Dilatata, Metzgeria Furcata and Radula Complanata). The Bryologist, 111(1): 84-97. https://doi.org/10.1639/0007-2745(2008)111[84:ASAECO]2.0.CO;2

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Friday Fellow: Scaly Lepidodermella

by Piter Kehoma Boll

From the longest animal seen last week, today we will see one of the shortest. Measuring only 190 µm in length, our fellow is called Lepidodermella squamata, which I turned into a “common” name as scaly lepidodermella.

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A specimen of Lepidodermella squamata. Photo by Giuseppe Vago.*

The scaly lepidodermella belongs to the phylum Gastrotricha, commonly known as hairybacks, which are all microscopic and distributed worldwide in aquatic environments. Found in freshwater environments worlwide, the scaly lepidodermella has the trunk covered in scales, hence its name. It feeds on other small organisms, such as algae, bacteria and yeast, as well as on detritus.

One of the most interesting aspects of the biology of the scaly lepidodermella is its reproduction. Although being hermaphrodite, this species usually produces only four eggs during its lifetime and those develop without fertilization. This means that the reproduction is parthenogenetic. However, strangely enough, the individuals become sexually mature after laying those four eggs, producing sperm and sometimes laying additional eggs, but most of those never hatch or, when they do, they produce offspring that rarely manage to become adults. Sexual reproduction, therefore, would be theoretically possible, but it has never been observed and there is no known means by which sperm could be transferred from one individual to the other.

This late sexual development may therefore be nothing but a vestige of its sexual past. Perhaps in future generations these traits will disappear and nothing but the perthenogenetic reproduction will last.

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References:

Hummon, M. R. (1984) Reproduction and sexual development in a freshwater gastrotrich 1. Oogenesis of parthenogenetic eggs (Gastrotricha). Zoomorphology 104(1): 33–41. https://dx.doi.org/10.1007/BF00312169

Hummon, M. R. (1986) Reproduction and sexual development in a freshwater gastrotrich 4. Life history traits and the possibility of sexual reproduction. Transactions of the American Microscopical Society 105(1): 97–109. https://dx.doi.org/10.2307/3226382

Wikipedia. Lepidodermella squamata. Available at <https://en.wikipedia.org/wiki/Lepidodermella_squamata&gt; Access on September 3, 2017.

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An extinct frog that is still living

by Piter Kehoma Boll

Hybrids, as you probably know, are organisms that arise from the mating of two individuals of different species. A mule, for example, is a well known hybrid between a horse and a donkey. Hybrids are usually sterile, although not all of them are, and some of them have a very peculiar way to continue to exist by using a process called hybridogenesis.

Hybrids that rely on hybridogenesis function in the following way: there are two original species, let’s call them A and B. When they copulate with each other, they produce a hybrid offspring, AB, which has half of the genes from one parent and half from the other. In “normal” hybrids, such creatures are completely sterile, unable to produce viable gametes, or can give rise to a new hybrid species by producing mixed gametes. However, in this peculiar kind of hybrids, called kleptons, things work differently.

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Pelophylax kl. hispanicus, the holder of a treasure. Photo by Andreas Thomsen.*

When kleptons are producing gametes, they never recombine the genomes of the two parents, but rather exclude the genome of one of them and produce gametes that contain the genome of the other parent. For example, the hybrid AB produces only A gametes, while the B genome is excluded. This means that if AB mates with a partner of the species A, the offspring will be formed by pure A individuals. If mating with B, the offspring will contain only new AB hybrids.

hybridogenesis_in_water_frogs

The edible frog Pelophylax kl. esculentus is a klepton formed by breeding P. lessonae and P. ridibundus. The klepton only produces gametes of P. ridibundus, eliminating the genome of P. lessonae during meiosis. (Photo by Wikimedia user Darekk2).**

This mode of reproduction is very common in frogs of the genus Pelophylax, as the example seen in the picture above. Another interesting point about kleptons is that they are usually unable to mate with another klepton. They rely one the parent species to reproduce, therefore “parasitizing” them.

A recently published paper on Pelophylax frogs reports a peculiar case in which one of the parent species is extinct. The klepton, known as Pelophylax kl. hispanicus, is the result of P. bergeri crossing with a now extinct species of Pelophylax. The case is that the gametes that P. kl. hispanicus produce are of the extinct species, but they can only fertilize gametes of P. bergeri. In other words, we could say that the extinct species is still alive inside the klepton, relying on P. bergeri to pass to the next generations.

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Pelophylax kl. hispanicus is a klepton that maintains the genome of an extinct species alive. Image extracted from Dubey & Dufresnes (2017).**

The authors suggest that perhaps we could find a way to bring the extinct species back, separated from P. bergeri. Although the result of crossing two P. kl. hispanicus is an sterile offspring, they think that continuous trials may end up revealing an eventual fertile offspring. Is it worth trying? Perhaps. But anyway, this is one more astonishing feature of nature, don’t you agree?

How many more extinct species may be living in a similar way, trapped in a hybrid?

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References:

Wikipedia. Hybridogenesis in water frogs. Available at <https://en.wikipedia.org/wiki/Hybridogenesis_in_water_frogs&gt;. Access on October 12, 2017.

Dubey, S.; Dufresnes, C. (2017) An extinct vertebrate preserved by its living hybridogenetic descendant. Scientific Reports 7: 12768. https://dx.doi.org/10.1038/s41598-017-12942-y

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Friday Fellow: Bootlace Worm

by Piter Kehoma Boll

Long ago I presented some of the extremes of the animal world, including the largest, the cutest and the leggiest. Now it’s time to introduce another extreme: the longest. And this animal is so long that it seems impossible. Its name: Lineus longissimus, commonly known as bootlace worm. Its length: up to 55 meters.

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An entangled bootlace worm. Photo by Bruno C. Vellutini.*

The bootlace worm is a member of the phylum Nemertea, commonly known as ribbon worms, and is found along the shores of the Atlantic Ocean in Europe. Most of the time, the worm is contracted, forming what looks like a heap of entagled wool threads that has no more than 30 cm from side to side. Although there are reports of specimens measuring more than 50 m, most of them are much shorter, with 30 m being already a very large size. Its width is of about 0.5 cm, so it is almost literally a long brown thread.

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Lineus longissimus photographed in Norway. Photo by Guido Schmitz.**

As all nemerteans, the bootlace worm is a predator and hunts its prey between the rocks on sandy shores, stunning them with its long poisonous proboscis and then swallowing them whole. Soft and fragile, the bootlace worm has no way to protect itself from predators using any physical defense, but it is known to have a series of different toxins on its epidermis, including some similar to the deadly pufferfish poison tetrodotoxin (TTX) that is produced by bacteria living in the mucus that surrounds the body of the worm.

Now, before leaving, take a look at this video of a bootlace worm swallowing a polychaete:

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References:

Cantell, C.-E. (1976) Complementary description of the morphology of Lineus longissimus (Gunnerus, 1770) with some remarks on the cutis layer in heteronemertines. Zoologica Scripta 5:117–120. https://dx.doi.org/10.1111/j.1463-6409.1976.tb00688.x

Carroll, S.; McEvoy, E. G.; Gibson, R. (2003) The production of tetrodotoxin-like substances by nemertean worms in conjunction with bacteria. Journal of Experimental Marine Biology and Ecology 288: 51–63. https://dx.doi.org/10.1016/S0022-0981(02)00595-6

Gittenberger, A.; Schipper, C. (2008) Long live Linnaeus, Lineus longissimus (Gunnerus, 1770) (Vermes: Nemertea: Anopla: Heteronemertea: Lineidae), the longest animal worldwide and its relatives occurring in The Netherlands. Zoologische Mededelingen. Leiden 82: 59–63.

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Friday Fellow: Lyre ship diatom

by Piter Kehoma Boll

It’s time for the next diatom, and just as with the radiolarian from the last week, it’s a hard task to find good pictures and good information of any species to present here.

Today I’m introducing a species of the most diverse (I guess, or at least one of the most diverse) genus of diatoms, Navicula, a name that means “little ship” in Latin due to the shape of the cells. There are more than 1200 species in this genus, and one of them is called Navicula lyra, which I decided to call the lyre ship diatom. I have also seen it with the name Lyrella lyra, being the type-species of a genus Lyrella (little lyre) that was split from Navicula. I don’t know which one is the official form today, but it seems that Lyrella is sometimes something like a subgenus of Navicula, although sometimes both genera are not even in the same family!

Navicula_lyra

Navicula lyra, a lyre little ship. Photo by Patrice Duros.*

Anyway, the lyre ship diatom is a planktonic species that is found in all the oceans of the world, being present in species lists everywhere. It measures about 100 µm or less, a typical size for a diatom.

As with other diatoms in the genera Navicula and Lyrella, the lyre ship diatom has different varieties, which may eventually be revealed to be separate species, I guess. See, for example, the variety constricta shown below. It looks considerably different from the picture above, which appears to be from the type variety.

Navicula_lyra

Lyrella lyra var. constricta. Extracted from Siqueiros-Beltrones et al. (2017)

Despite being a widespread species, little seems to be known about the natural history of the lyre ship diatom. Aren’t you interested in studying the ecology of these tiny little glass ships?

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References:

Nevrova, E.; Witkowski, A.; Kulikovskiy, M.; Lange-Bertalot, H.; Kociolek, J. P. (2013) A revision of the diatom genus Lyrella Karayeva (Bacillariophyta: Lyrellaceae) from the Black Sea, with descriptions of five new species. Phytotaxa 83(1): 1–38.

Siqueiros-Beltrones, D. A.; Argumedo-Hernández, U.; López-Fuerte, F. O. (2017) New records and combinations of Lyrella (Bacillariophyceae: Lyrellales) from a protected coastal lagoon of the northwestern Mexican Pacific. Revista Mexicana de Biodiversidad 88(1): 1–20.

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The natural-unnatural fallacy: let’s stop with this bullshit

by Piter Kehoma Boll

This post may upset some people, perhaps people from very different backgrounds and very different points of view regarding society or human practices, but I feel that I have to discuss this subject that has been used as a way to justify or condemn some behaviors.

Everybody has already heard, and perhaps even uses, the argument of “this is not natural” as a justification to oppose something. You can hear homophobes use it to condemn homosexuality, vegans to condemn the ingestion of meat, or even old people to lament the death of a child. It is sometimes called “argumentum ad naturam” or “appeal to nature”, a fallacy that considers that something natural is always better than something unnatural.

When a homophobe says that he or she is against homosexuality because it is not natural, their oppositors, people who defend the freedom of sexuality, quickly present them with evidences of homosexuality in other species. I myself, being a gay man, used, in the past, examples of other gay animals to explain that homosexuality is indeed natural.

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Oh, yeah, babe. Two male lions having sex. Photo by Wikimedia user Rufus46.*

Regarding human diet, we can find the same thing, including two opposite groups using this very same argument. You can see vegetarians advocating against the consumption of meat because of our dentition or intestine, which are not typical of a carnivorous species. On the other hand, people who defend the so-called “paleo” diet try to reconstruct a diet that was common to our pre-historical ancestors, which would be our “natural” diet, and thus they consume large amounts of meat and fruits and avoid consuming grains, large amounts of sugar or other food that need to be domesticated. In the same way, other people, such as vegans (and even paleo lovers) are against consuming milk because this is a baby food and should not be ingested by adult mammals, afterall “it is not natural” to take the milk of a female of another species and drink it.

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Several ant species “milk” aphids to drink the sweet secretions (honeydew) that they release. Photo by Friedrich Böhringer.**

Now let me tell you something: this all means shit. This is not how things work in the real world, which by the way is the same as nature. When we use the argument of something being natural or unnatural, we are implying that there is a pre-established way for things to work, that there is a purpose in life. Well, there is not! Do you know natural selection, right? Well, it basically states that the most successful variations of something are the ones that will survive, regardless of what they are or how they are used. The mouth evolved primarily as an opening through which animals ingest food, but we use our mouths to many different things, such as to speak, breathe, kiss, hold things, or give blowjobs. Are those things unnatural? Who cares? As long as the mouth is good at doing it, it will continue to be used to do it.

And more than that, using other species as a comparison to things that are natural or not for humans is ridiculous. Just because we are the only species that write, is writing unnatural? If we consider that to be true, then we can apply it to find unnatural behaviors in any other species. As long as a behavior is only found in a single species, it would be unnatural.

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The satin bowerbird is the only species that uses blue objects to decorate its bower in order to attract a female. Is its behavior unnatural because of that? Photo by Joseph C Boone.***

As a social and (supposedly) scientific species, we should consider a behavior as good or bad based on its consequences to society or to individuals, as well as to the world as a whole. Murdering is bad not because it is unnatural, but because it kills people! Pollution is not bad because it is unnatural, it is bad because it pollutes! So more than only being stupid because of its assumption that natural things are good and unnatural things are not, the appeal to nature is also stupid because there is no way to separate things in natural and unnatural. Let’s grow up intellectually and stop using this bullshit of an argument at all.

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Friday Fellow: Twisted-Spined Sponge Radiolarian

by Piter Kehoma Boll

Oh, it’s time for our next radiolarian. As as usual, it’s hard to find good information on any species. (If you work with radiolarians and have good available resources and nice species to suggest, please contact us!)

It’s hard to find pictures of live radiolarians, especially those identified to the species level, but one that I found is seen below and is called Spongosphaera streptacantha, or the twisted-spined sponge radiolarian, as I decided to call it.

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A nice photo of a liveSpongosphaera streptacantha. Extracted from Galerie de l’Observatoire Océanologique de Villefranche-sur-Mer.

The twisted-spined sponge radiolarian is found in warm waters in the Atlantic and Pacific oceans (perhaps the Indian too?) and, as one can notice, may have a diameter of more than 1 mm if we count the longest spines. As with most radiolarians, the cell of this species has two concentric shells and a set of spines, which are 6 to 15 in number.

The food of the twisted-spined sponge radiolarian consists of smaller organisms, such as bacteria and algae, which it captures with the long rod-like pseudopods called actinopodia.

As with most radiolarians, the twisted-spined sponge radiolarian is understudied regarding its ecology. Let’s hope more people get interested in studying this fascinating group of organisms.

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References:

Kurihara, T.; Matsuoka, A. (2004) Shell structure and morphological variation in Spongosphaera streptacantha Haeckel (Spumellaria, Radiolaria). Science Reports of Niigata University (Geology), 19: 35–48. http://hdl.handle.net/10191/2141

Matsuoka, A. (2007) Living radiolarian feeding mechanisms: new light on past marine ecosystems. Swiss Journal of Geosciences, 100: 273-279. https://dx.doi.org/10.1007/s00015-007-1228-y

Radiolaria.org: Spongosphaera streptacantha. Available at: < http://www.radiolaria.org/species.htm?sp_id=90 >. Access on August 8, 2017.

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