Category Archives: Zoology

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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The hammerhead flatworms: once a mess, now even messier

by Piter Kehoma Boll

Few people know that land planarians exist, but when they do, they most likely know the hammerhead flatworms, which comprise the subfamily Bipaliinae.

The hammerhead flatworms, or simply hammerhead worms, have this name because their head has lateral expansions that make them resemble a hammer, a shovel or a pickaxe. Take a look:

Bipalium_vagum

The “wandering hammerhead worm”, Bipalium vagum. Notice the peculiar head. Photo by flickr user budak.*

The Chinese knew the hammerhead worms at least since the 10th century, which is understandable, since they are distributed from Japan to Madagascar, including all southern and southeast Asia, as well as Indonesia, the Philippines and other archipelagos. The western world, however, first heard of them in 1857, when William Stimpson described the first species and put them in a genus called Bipalium, from Latin bi- (two) + pala (shovel), due to the head shape. One of them was the species Bipalium fuscatum, a Japanese species that is currently considered the type species of the genus.

800px-bipalium_fuscatum_by_head

Anterior region of Bipalium fuscatum, the “brownish hammerhead worm”. Photo by Wikimedia user 根川大橋.**

Two years later, in 1859, Ludwig K. Schmarda described one more species, this one from Sri Lanka, and, unaware of Stimpson’s paper, called the species Sphyrocephalus dendrophilus, erecting the new genus for it from Greek sphȳra (hammer) + kephalē (head).

Sphyrocephalus_dendrophilus

Drawings by Schmarda of Sphyrocephalus dendrophilus.

In the next year, 1860, Edward P. Wright did something similar and described some hammerhead worms from India and China, creating a new genus, Dunlopea, for them. The name was a homage to his friend A. Dunlop (whoever he was).

Dunlopea_grayia

Wright’s Drawing of Dunlopea grayia (now Diversibipalium grayi) from China.

Eventually those errors were perceived and all species were put in the genus Bipalium, along with several others described in the following years. All hammerhead worms were part of the genus Bipalium until 1896, when Ludwig von Graff decided to improve the classification and divided them into three genera:

1. Bipalium: With a head having long “ears”, a well developed head.
2. Placocephalus (“plate head”): With a more semicircular head.
3. Perocephalus (“mutilated head”): With a shorter, rudimentary head, almost as if it had been cut off.

Bipaliids

Compare the heads of typical species of Bipalium (left), Placocephalus (center) and Perocephalus (right), according to Graff.

This system, however, was soon abandoned and everything went back to be simply Bipalium and continued that way for almost a century, changing again only in 1998, when Kawakatsu and his friends started to mess with the penises of the hammerhead worms.

First, in 1998, they erected the genus Novibipalium (“new Bipalium“) for species with a reduced or absent penis papilla, and retained in Bipalium those with a “well”-developed penis papilla. It is worth noticing though that this well-developed papilla is not much bigger than a reduced papilla in Novibipalium. In both genera the actual, functional penis is formed by a set of folds in the male atrium and not by the penis papilla itself as in other land planarians that have a penis papilla.

Later, in 2001, Ogren & Sluys separated some more species of Bipalium in a new genus called Humbertium (after Aloïs Humbert, who described most species of this new genus). They were separated from Bipalium because the ovovitelloducts (the ducts that conduct the eggs and vitellocites) enter the female atrium from ahead, and not from behind as in the typical Bipalium. This separation is, in my opinion, more reasonable than the previous one.

Now we had three genera of hammerhead worms based on their internal anatomy, but several species were described without any knowledge of their sexual organs. Thus, in 2002, Kawakatsu and his friends created one more genus, Diversibipalium (the “diverse Bipalium“) to include all species whose anatomy of the sexual organs was unknown. In other words, it is a “wastebasket” genus to place them until they are better studied.

Are these three genera, Bipalium, Novibipalium and Humbertium, as now defined, natural? We still don’t know, but I bet they are not. A good way to check it would be by using molecular phylogeny, but we don’t have people working with these animals in their natural habitats, so we do not have available material for that. Another thing that can give us a hint is to look at their geographical distribution. We can assume that genetically similar species, especially of organisms with such a low dispersal ability as land planarians, all occur in the same geographical region, right? So where do we find species of each genus? Let’s see:

Bipalium: Indonesia, Japan, China, Korea, India.

Novibipalium: Japan.

Humbertium: Madagascar, Sri Lanka, Southern India, Indonesia.

Weird, right? They are completely mixed and covering a huge area of the planet, especially when we consider Humbertium. We can see a tendency, but nothing very clear.

Fortunately, some molecular analyses were published (see Mazza et al. (2016) in the references). One, which included the species Bipalium kewense, B. nobile, B. adventitium, Novibipalium venosum and Diversibipalium multilineatum placed Diversibipalium multilineatum very close to Bipalium nobile, and they are in fact very similar, so I guess that we can transfer it from Diversibipalium to Bipalium, right? Similary, Novibipalium venosum appears mixed with the species of Bipalium. I guess this is kind of messing things up one more time.

681px-bipalia_invasive

Head of some species of Bipalium, including the ones used in the study cited above. Unfortunately, I couldn’t find a photo or drawing of Novibipalium venosum. Image by myself, Piter Kehoma Boll.**

Interestingly, among the analyzed species, the most divergent was Bipalium adventitium, whose head is “blunter” than that of the other ones. Could the head be the answer, afterall? Let’s hope that someone with the necessary resources is willing to solve this mess soon.

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See also:

Once found and then forgotten: the not-so-bright side of taxonomy.

The lack of taxonomists and its consequences on ecology.

They only care if you are cute. How charisma harms biodiversity.

The faboulous taxonomic adventure of the genus Geoplana.

Darwin’s Planaria elegans: hidden, extinct or misidentified?

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References:

Graff, L. v. (1896) Über das System und die geographische Verbreitung der Landplanarien. Verhandlungen der Deutschen Zoologischen Gesellschaft6: 61–75.

Graff, L. v. (1899) Monographie der Turbellarien. II. Tricladida Terricola (Landplanarien). Engelmann, Leipzig.

Kawakatsu, M.; Ogren, R. E.; Froehlich, E. M. (1998) The taxonomic revision of several homonyms in the genus Bipalium, family Bipaliidae (Turbellaria, Seriata, Tricladida, Terricola). The Bulletin of Fuji Women’s College Series 236: 83–93.

Kawakatsu, M.; Ogren, R. E.; Froehlich, E. M., Sasaki, G.-Y. (2002) Additions and corrections of the previous land planarians indices of the world (Turbellaria, Seriata, Tricladida, Terricola). The bulletin of Fuji Women’s University. Ser. II40: 162–177.

Mazza, G.; Menchetti, M.; Sluys, R.; Solà, E.; Riutort, M.; Tricarico, E.; Justine, J.-L.; Cavigioli, L.; Mori, E. (2016) First report of the land planarian Diversibipalium multilineatum (Makino & Shirasawa, 1983) (Platyhelminthes, Tricladida, Continenticola) in Europe. Zootaxa4067(5): 577–580.

Ogren, R. E.; Sluys, R. (2001) The genus Humbertium gen. nov., a new taxon of the land planarian family Bipaliidae (Tricladida, Terricola). Belgian Journal of Zoology131: 201–204.

Schmarda, L. K. (1859) Neue Wirbellose Thiere beobachtet und gesammelt auf einer Reise um die Erde 1853 bis 1857 1. Turbellarien, Rotatorien und Anneliden. Erste Hälfte. Wilhelm Engelmann, Leipzig.

Stimpson, W. (1857) Prodromus descriptionis animalium evertebratorum quæ in Expeditione ad Oceanum, Pacificum Septentrionalem a Republica Federata missa, Johanne Rodgers Duce, observavit er descripsit. Pars I. Turbellaria Dendrocœla. Proceedings of the Academy of Natural Sciences of Philadelphia9: 19–31.

Wright, E. P. (1860) Notes on Dunlopea. Annals and Magazine of Natural History, 3rd ser.6: 54–56.

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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.

797px-lepidodermella_squamatum

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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Darwin’s Planaria elegans: hidden, extinct or misidentified?

by Piter Kehoma Boll

During his epic voyage on the Beagle, Charles Darwin visited Rio de Janeiro, Brazil, and collected some amazing land planarians, a group that until then was very little known. One of the species he found was Geoplana vaginuloides, the type-species of the genus Geoplana, at that time named Planaria vaginuloides.

f6387-vaginuloides-pedrabranca40

Geoplana vaginuloides (Darwin, 1844), the first Brazilian land planarian species to be described. Photo by Fernando Carbayo.*

The second species described by Darwin was named Planaria elegans. Darwin’s description is as it follows:

“Position of the orifices as in P. vaginuloides. Anterior part of the body little elongated. Ocelli absent on the anterior extremity, and only a few round the margin of the foot. Colours beautiful; back snow-white, with two approximate lines of reddish brown; near the sides with several very fine parallel lines of the same tint; foot white, exteriorly clouded, together with the margin of the body, with pale blackish purple: body crossed by three colourless rings, in the two posterior of which the orifices are situated. Length 1 inch; breadth more uniform, and greater in proportion to length of the body, than in last species.
Hab. Same as in P. vaginuloides. [Rio de Janeiro]”

And this is all we know about this species. Darwin did not provide any drawing and later researchers did not report this species again, except when mentioning Darwin’s publication. As you can see by the description, it is not very accurate. He does not say what is the breadth of each line or band, neither how many of the “several fine parallel lines of the same tint” there are. Here is a quick drawing I did of how I imagine the creature would be:

image description

My idea of what Darwin’s Planaria elegans may have looked like. Head to the left. Credits to myself, Piter Kehoma Boll.**

In 1938, Albert Riester described a land planarian from Barreira, a district in the city of Teresópolis, Rio de Janeiro, naming it Geoplana barreirana. He described it as it follows (translated from the original in German):

“Land planarian found on a leaf after a rain; greatest lenght ca. 20 mm. Middle of the back white with two fine purple-red (atropurpureus light) parallel stripes. Outside of the white also limitted by pale red, then follows (on both sides) a black band and laterally a black-brown marmorate pattern over brown background. The middle stripe ends at the rear [end]. Head spotted, marked with transversal spotted bands (regenerate?). Underside gray, bordered by black-brown. Anterior end is arched backwards.”

Fortunately, Riester provided a drawing, which you can see below:

Barreirana_barreirana_Riester

Geoplana barreirana drawn by Riester (1938).

They look a bit alike, right? Fortunately Geoplana barreirana (currently named Barreirana barreirana) was found by later researchers and we have photographs! See one specimen below:

f6284_barreiranatijuca3

A specimen of Barreirana barreirana found in the Tijuca National Park, Rio de Janeiro. Photo by Fernando Carbayo.*

Riester did not describe any transversal marks on his specimens, but he may have mistaken them for color loss in preserved specimens or something like that. Otherwise the specimen looks very similar to Riester’s drawing, and the internal anatomy, which Riester provided as well, is also compatible.

Now let’s try to fit Darwin’s description of Planaria elegans in this photograph. White background, two reddish brown stripes and several fine parallel stripes of the same tint. He likely described the animals from preserved specimens, even though he have seen them alive and collected them. Perhaps the colors had already faded a little and the black stripes, which internally touch two of the reddish stripes, may have been considered a single purple-red stripe? It is not clear, in his description, whether there is white between the “reddish brown” stripes and the “pale blackish-purple” sides, as I did in my drawing, or not, as in Barreirana barreiranabut certainly the dark gray sides of B. barreirana could be the same as the pale blackish purple sides of Planaria elegans, don’t you think? And B. barreirana HAS three white “rings” crossing the body. You can see the first and the second very clearly on the specimen above. The third one is not very well marked, but you can see a third white mark interrupting the gray sides. And the second and almost third marks seem to be quite where one would expect the two orifices (mouth and gonopore) of the planarian to be!

And what about the ventral side? Darwin described P. elegan‘s as being white with a pale blackish purple border as the sides of the dorsum. Riester described G. barreirana‘s as being gray bordered by black-brown. Here is Barreirana barreirana‘s ventral side:

Barreirana barreirana from below

Ventral side of Barreirana barreirana from the Tijuca National Park, Rio de Janeiro. Photo by Fernando Carbayo.*

It is white, or pale gray perhaps, and the borders are of the same color as the sides of the dorsum!

I think it is very, very likely that Darwin’s Planaria elegans and Riester’s Geoplana barreirana are the same species. The fact that no one but Darwin has ever seen a specimen of Planaria elegans makes it even more likely.

What do you think?

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See also:

How are little flatworms colored? A Geoplana vaginuloides analysis.

The fabulous taxonomic adventure of the genus Geoplana.

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References:

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 14, 241–251.

Riester, A. (1938) Beiträge zur Geoplaniden-Fauna Brasiliens. Abhandlungen der senkenbergischen naturforschenden Gesellschaft 441, 1–88.

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Friday Fellow: Common Water Bear

by Piter Kehoma Boll

Tiny and tough, our newest Friday Fellow can be found hidden among the moss throughout most of the planet, and perhaps even beyond it, for if there is a species to which space is a piece of cake, that species is the common water bear Milnesium tardigradum.

783px-sem_image_of_milnesium_tardigradum_in_active_state_-_journal-pone-0045682-g001-2

A Scaning Electron Microscope (SEM) image of a specimen of the common water bear in its active state. Photo extracted from Schokraie et al. (2012).*

You may have already heard of tardigrades or water bears, tiny chubby animals that are able to withstand the harsher conditions, such as intense desiccation, radiation and even the vacuum of outer space. Most of the data regarding the toughness of these organisms comes from the common water bear, the most widespread species of the phylum Tardigrada.

Measuring up to 0.7 mm in length, the common water bear has eight legs with claws on their end and is considered a predator, feeding on a variety of other small organisms, including algae, rotifers and nematodes. It has a worldwide distribution and is commonly found living on moss, such as the cosmopolitan silvergreen moss already presented here.

As members of the supergroup Ecdysozoa (which also includes arthropods and roundworms), tardigrades undergo ecdysis, also commonly known as molting, a process through which they shed their exoskeleton. In the common water bear, females always lay eggs around the time of molting. Before leaving the old exoskeleton, the females lay the clutch of eggs, which may vary from 1 to 12 eggs, between the old and the new exoskeleton and usually remain inside the old exoskeleton several hours after laying the eggs. When they finally leave, the eggs remain inside the shed skin, which perhaps helps them to be more protected from danger.

Milnesium_tardigradum

A clutch of seven eggs is left in the empty exoskeleton while the female leaves. Photo by Carolina Biological Supply Company.**

When the habitat of the common water bear gets dry, it enters in a state called cryptobiosis, in which the body shrinks and the metabolism stops. Under this state, known as tun, it can withstand high doses of radiation and both high and zero air pressure, surviving even in the environment of outer space. It is not invincible, however. Radiation in doses above 1000 Gy may not always kill them, but always let them sterile, which is, evolutionary, basically the same thing.

615px-sem_image_of_milnesium_tardigradum_in_tun_state_-_journal-pone-0045682-g001-3

SEM image of the common water bear in the tun state. Photo extracted from Schokraie et al. (2012).*

Nevertheless, the American cockroach is just an amateur regarding survival when compared to the common water bear.

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References:

Horikawa, D. D.; Sakashita, T.; Katagiri, C.; et al. (2009) Radiation tolerance in the tardigrade Milnesium tardigradumInternatonal Journal of Radiation Biology, 86(12): 843–848. http://dx.doi.org/10.1080/09553000600972956

Schokraie E, Warnken U, Hotz-Wagenblatt A, Grohme MA, Hengherr S, et al. (2012) Comparative proteome analysis of Milnesium tardigradum in early embryonic state versus adults in active and anhydrobiotic state. PLoS ONE 7(9): e45682. https://dx.doi.org/10.1371/journal.pone.0045682

Suzuki, A. C. (2003) Life history of Milnesium tardigradum Doyère (Tardigrada) under a rearing environment. Zoological Science 20(1): 49–57. https://doi.org/10.2108/zsj.20.49

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They only care if you are cute: how charisma harms biodiversity

by Piter Kehoma Boll

Which of the two species shown below is more charismatic?

Tangara_chilensis

Tangara chilensis (Paradise Tanager). Photo by flickr user ucumari.*

854px-apocrypta_guineensis2c_volw-wyfie_op_f_sur2c_manie_vd_schijff_bt2c_f

Apocrypta guineensis (a fig wasp). Photo by Wikimedia user JMK.**

You probably would pick the first one. And if I’d ask you which one deserves more attention and efforts to be preserved, you would likely choose the bird as well, or at least most people would. But what is the problem with that? That’s what I am going to show you now.

As we all know, the protection of biological diversity is an important subject in the current world. Fortunately, there is an increase in campaigns promoting the preservation of biodiversity, but unfortunately they are almost always directed to a small subset of species. You may find organizations seeking to protect sea turtles, tigers, eagles or giant pandas, but can you think of anyone wanting to protect beetles? Most preservation programs target large and charismatic creatures, such as mammals, birds and flowering plants, while smaller and not-so-cute organisms remain neglected. And this is not only true in environments that included non-biologist people, but in all fields of research. And more than only leading to a bias in the protection of ecosystems, this preference leads to thousands of understudied species that could bring biotechnological revolutions to humandkind.

In an interesting study published this week in Nature’s Scientific Reports (see reference below), Troudet et al. analyzed the taxonomic bias in biodiversity data by comparing the occurrence of data on several taxonomic groups to those groups’ diversity. The conclusions are astonishing, although not that much surprising. The most charismatic groups, such as birds, are, one could say, overstudied, with an excess of records, while other, such as insects, are highly understudied. While birds have about 200 million occurences above the ideal record, insects have about 200 million below the ideal number. And the situation does not seem to have improved very much along the years.

41598_2017_9084_fig1_html

The bias in interest is clear. The vertical line indicates the “ideal” number of occurrences of each group. A green bar indicates an excess of occurrences, while a red bar indicates a lack of occurrences. Birds and Insects are on the opposite extremes, but certainly the insect bias is much worse. Figure extracted from Troudet et al. (2017).***

Aditionally, the study concluded that the main reason for such disparity is simply societal preference, i.e., the most studied groups are the most loved ones by people in general. The issue is really a simple matter of charisma and has little to do with scientific or viability reasons.

The only way to change this scenario is if we find a way to raise awareness and interest of the general public on the less charismatic groups. We must make them interesting to the lay audience in order to receive their support and increase the number of future biologists that will choose to work with these neglected but very important creatures.

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See also:

Once found and then forgotten: the not so bright side of taxonomy

The lack of taxonomists and its consequences on ecology

Unknown whereabouts: the lack of biogeographic references of species

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Reference:

Troudet, J.; Grandcolas, P.; Blin, A,; Vignes-Lebbe, R.; Legendre, F. (2017) Taxonomic bias in biodiversity data and societal preferences. Scientific Report 7: 9132. https://dx.doi.org/10.1038/s41598-017-09084-6

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Friday Fellow: Sea Swallow

by Piter Kehoma Boll

As the second species of today, I’m bringing a terrible but beautiful predator of the Portuguese man o’ war, the sea swallow Glaucus atlanticus, which is, in my opinion, one of the most beautiful sea creatures.

Glaucus_atlanticus

Isn’t it a magnificent creature? Photo by Sylke Rohrlach.*

Also known as blue dragon, blue glaucus and many other names, the sea swallow is a small sea slug that measures up to 3 cm in length as an adult. This species is pelagic, meaning that it lives in the open ocean, neither close to the bottom nor close to the shore.  Although it is found in all three oceans, genetic evidences indicate that the populations from the Atlantic, the Pacific and the Indian oceans have diverged more than 1 million years ago.

The sea swallow has a gas-filled sac in the stomach that makes it float upside down in the water, meaning that its ventral side is directed upward. The wide blue-bordered band running along the body, as seen in the picture above, is the slug’s foot. It’s dorsal side, which is directed downward, is completely white or light gray.

Being a carnivorous species, the sea swallows feeds on several cnidarian species, especially the Portuguese man o’ war. It usually collects the cnidocytes (the sting cells) of its prey and put them on its own body, so that it becomes as stingy as or even stingier than its prey. If you find one lying on the beach, be careful.

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References:

Churchull, C. K. C.; Valdés, Á.; Foighil, D. Ó (2014) Afro-Eurasia and the Americas present barriers to gene flow for the cosmopolitan neustonic nudibranch Glaucus atlanticus. Marine Biology, 161(4): 899-910.

Wikipedia. Glaucus atlanticus. Available at < https://en.wikipedia.org/wiki/Glaucus_atlanticus >. Access on June 18, 2017.

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