Tag Archives: worms

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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Land snails on islands: fascinating diversity, worrying vulnerability

by Piter Kehoma Boll

The class Gastropoda, which includes snails and slugs, is only beaten by the insects in number of species worldwide, having currently about 80 thousand described species. Among those, about 24 thousand live on land, where they are a very successful group, especially on oceanic islands.

The Hawaiian Islands alone, for example, have more than 750 snail species and there are more than 100 endemic species in the small island of Rapa in the South Pacific. This diversity is much higher than that in any continental place, but the reason for that is not completely understood.

Mandarina

A land snail of the genus Mandarina, endemic to the Ogasawara Islands, Japan. Photo by flickr user kmkmks (Kumiko).*

One of the most likely explanations for this huge diversity on islands is related to the lack of predators. The most common predators of snails include birds, mammals, snakes, beetles, flatworms and other snails. Most of those are not present in small and isolated islands, which allows an increase in land snail populations in such places. Without too much dangers to worry about, the community of land snails n islands can explore a greater range of niches, eventually leading to speciation.

Unfortunately, as always, the lack of danger leads to recklessness. Without predators to worry about, insular land snails tend to lay fewer eggs than their mainland relatives. If there is no danger of having most of your children eaten, why would you have that many? It is better to lay larger eggs, putting more resources on fewer babies, and so assure that they will be strong enough to fight against other snail species. Afterall, the large number of species in such a small place as an island likely leads to an increased amount of competition between species.

But why is this recklessness? Well, because you never known when a predator will arrive. And they already arrived… due to our fault.

The diversity of insular land nails was certainly affected by habitat loss promoted by humans, but also by predators that we carried with us to the islands, whether intentionally or not. These predators include rats, the predatory snail Euglandina rosea and the land flatworm Platydemus manokwari, the latter being most likely the worst of all.

800px-platydemus_manokwari

The flatworm Platydemus manokwari in the Ogasawara Islands. Photo by Shinji Sugiura.

This flatworm arrived at the Chichijima Island, part of the Ogasawara Islands in the Pacific Ocean, in the early 1990s and in about two decades it led most land snail species on the island to extinction and many more are about to face the same fate on this island and on others. Not being prepared for predators, these poor snails cannot reproduce fast enough to replace all individuals eaten by the flatworm.

We have to act quickly if we want to save those that are still left.

See also: The New Guinea flatworm visits France – a menace.

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ResearchBlogging.orgReferences and further reading:

Chiba, S., & Cowie, R. (2016). Evolution and Extinction of Land Snails on Oceanic Islands. Annual Review of Ecology, Evolution, and Systematics, 47 (1), 123-141 DOI: 10.1146/annurev-ecolsys-112414-054331

Sugiura, S., Okochi, I., & Tamada, H. (2006). High Predation Pressure by an Introduced Flatworm on Land Snails on the Oceanic Ogasawara Islands. Biotropica, 38 (5), 700-703 DOI: 10.1111/j.1744-7429.2006.00196.x

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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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The history of Systematics: Animals in Systema Naturae, 1758 (part 4)

by Piter Kehoma Boll

This is the fourth and last part of this series of posts. See here part 1, part 2 and part 3.

I’m presenting here the 6 th and last class of animals: Vermes. It included basically anything that was neither a vertebrate nor an arthropod.

6. Vermes (worms)

Heart with one ventricle and one auricle; cold pus.
Spiracles absent?
Jaws multiple, various.
Penises several in hermaphrodites, androgynous.
Senses: tentacles, head absent (rarely with eyes, no ears and nostrils).
Covering: sometimes calcareous or absent, if not spines.
Support: neither feet nor fins.

Vermes were classified according the form of the body in 5 orders: Intestina, Mollusca, Testacea, Lithophyta and Zoophyta.

6.1 Intestina (internal ones or intestines), simple, naked and without appendages: Gordius (horsehair worms), Furia (the legendary worm), Lumbricus (earthworms and lugworms), Ascaris (roundworms and pinworms), Fasciola (liver flukes), Hirudo (leeches), Myxine (hagfishes) and Teredo (shipworms).

Linnaeus’ heterogeneous order Intestina included (from left to right, top to bottom) the water horsehair worm (Gordius aquaticus), the legendary hell’s fury (Furia infernalis), the common earthworm (Lumbricus terrestris), the giant roundworm (Ascaris lumbricoides), the sheep liver fluke (Fasciola hepatica), the European medicinal leech (Hirudo medicinalis), the Atlantic hagfish (Myxine glutinosa), and the naval shipworm (Teredo navalis). Credits to Jiří Duchoň (horsehair worm), Michael Linnenbach (earthworm), Wikimedia user GlebK (leech), Arnstein Rønning (hagfish), Poi Australia [poi-australia.com.au] (shipworm).

Linnaeus’ heterogeneous order Intestina included (from left to right, top to bottom) the water horsehair worm (Gordius aquaticus), the legendary hell’s fury (Furia infernalis), the common earthworm (Lumbricus terrestris), the giant roundworm (Ascaris lumbricoides), the sheep liver fluke (Fasciola hepatica), the European medicinal leech (Hirudo medicinalis), the Atlantic hagfish (Myxine glutinosa), and the naval shipworm (Teredo navalis). Credits to Jiří Duchoň (horsehair worm), Michael Linnenbach (earthworm), Wikimedia user GlebK (leech), Arnstein Rønning (hagfish), Poi Australia [poi-australia.com.au] (shipworm).

 6.2 Mollusca (soft ones), simple, naked and with appendages: Limax (land slugs), Doris (doriid sea slugs), Tethys (tethydid sea slugs), Nereis (polychaetes), Aphrodita (sea mice), Lernaea (anchor worms), Priapus (priapulid worms and anemones), Scyllaea (scyllaeid sea slugs), Holothuria (salps and man o’ wars), Triton (possibly some sort of sea slug), Sepia (octopuses, squids and cuttlefishes), Medusa (jellyfishes), Asterias (starfishes), Echinus (sea urchins and sand dollars).

Among the animals that Linnaeus put under Mollusca are (from left to right, top to bottom) the leopard slug (Limax maximus), the warty dorid (Doris verrucosa), the fringed tethydid (Tethys leporina, now Tethys fimbria), the slender ragworm (Nereis pelagica), the sea mouse (Aphrodita aculeata), the common anchor worm (Lernaea cyprinacea), the cactus worm (Priapus humanus, now Priapulus caudatus), the sargassum nudibranch (Scyllaea pelagica), the Portuguese man o’ war (Holothuria physalis, now Physalia physalis), the common cuttlefish (Sepia officinalis), the moon jellyfish (Medusa aurita, now Aurelia aurita), and the European edible sea urchin (Echinus esculentus).Credits to Marina Jacob (slug), Wikimedia user Seascapeza (dorid), Pino Bucca (tethydid), Alexander Semenov (ragworms), Michael Maggs (sea mouse), glsc.usgs.gov (anchor worm), Shunkina Ksenia (cactus worm), Universidad de Olviedo (sargassum nudibranch), Hans Hillewaert (cuttlefish, jellyfish and starfish), and Bengt Littorin (sea urchin).

Among the animals that Linnaeus put under Mollusca are (from left to right, top to bottom) the leopard slug (Limax maximus), the warty dorid (Doris verrucosa), the fringed tethydid (Tethys leporina, now Tethys fimbria), the slender ragworm (Nereis pelagica), the sea mouse (Aphrodita aculeata), the common anchor worm (Lernaea cyprinacea), the cactus worm (Priapus humanus, now Priapulus caudatus), the sargassum nudibranch (Scyllaea pelagica), the Portuguese man o’ war (Holothuria physalis, now Physalia physalis), the common cuttlefish (Sepia officinalis), the moon jellyfish (Medusa aurita, now Aurelia aurita), the common starfish (Asterias rubens), and the European edible sea urchin (Echinus esculentus). Credits to Marina Jacob (slug), Wikimedia user Seascapeza (dorid), Pino Bucca (tethydid), Alexander Semenov (ragworm), Michael Maggs (sea mouse), glsc.usgs.gov (anchor worm), Shunkina Ksenia (cactus worm), Universidad de Olviedo (sargassum nudibranch), Hans Hillewaert (cuttlefish, jellyfish and starfish), and Bengt Littorin (sea urchin).

6.3 Testacea (covered with a shell), simple, covered by a calcareous shelter: Chiton (chitons), Lepas (barnacles), Pholas (piddocks and angelwings), Myes (soft-shell clams), Solen (razor clams), Tellina (tellins), Cardium (cockles), Donax (wedge shells), Venus (venus clams), Spondylus (thorny oysters), Chama (jewel box shells), Arca (ark clams), Ostrea (true oysters), Anomia (saddle oysters), Mytilus (mussels), Pinna (pen shells), Argonauta (paper nautiluses), Nautilus (nautiluses), Conus (cone snails), Cypraea (cowries), Bulla (bubble shells), Voluta (volutes), Buccinum (true whelks), Strombus (true conchs), Murex (murex snails), Trochus (top snails), Turbo (turban snails), Helix (land snails), Nerita (nerites), Haliotis (abalones), Patella (limpets and brachiopods), Dentalium (tusk shells) and Serpula (serpulid worms and worm snails).

Linnaeus’ diverse order Testacea included (from left to right, top to bottom): the West Indian green chiton (Chiton tuberculatus), the smooth gooseneck barnacle (Lepas anatifera), the common piddock (Pholas dactylus), the sand gaper (Myes arenaria, now Mya arenaria), the sheath razor (Solen vagina), the sunrise tellin (Tellina radiata), the great ribbed cockle (Cardium costatum), the abrupt wedge shell (Donax trunculus), the wary venus (Venus verrucosa), the spiny scallop (Spondylus gaederopus), the lazarus jewel box (Chama lazarus), the Noah’s Ark shell (Arca noae), the European flat oyster (Ostrea edulis), the European jingle shell (Anomia ephippium), the blue mussle (Mytilus edulis), the rough penshell (Pinna rudis), the greater argonaut (Argonauta argo), the chambered nautilus (Nautilus pompilius), the marbled cone (Conus marmoreus), the tiger cowry (Cypraea tigris), the Pacific bubble (Bulla ampulla), the music volute (Voluta musica), the common whelk (Buccinum undatum), the West Indian fighting conch (Strombus pugilis), the caltrop murex (Murex tribulus), maculated top snail (Trochus maculatus), the tapestry turban (Turbo petholatus), the Roman snail (Helix pomatia), the bleeding tooth nerite (Nerita peloronta), Midas ear abalone (Haliotis midae), the Mediterranean limpet (Patella caerulea), the elephant tusk shell (Dentalium elephantinum), the sand worm snail (Serpula arenaria, now Thylacodes arenarius). Credits to James St. John (chiton), Ruben Vera (barnacle), Valter Jacinto (piddock), Oscar Bos [ecomare.nl] (sand gaper), Guido & Philippe Poppe [conchology.be] (razor), femorale.com (tellin, cockle, scallop, ark shell, jingle shell, bubble, fighting conch, nerite, abalone, tusk shell), Hans Hillewaert (wedge shell, venus, nautilus, whelk), Richard Parker (jewel box, marbled cone), Jan Johan ter Poorten (oyster), Wikimedia user Hectonichus (penshell, volute), Bernd Hoffmann (argonaut), Samuel Chow (cowry), Frédéric Ducarme (turban), H. Krisp (Roman snail), Wikimedia user Esculapio (limpet), Matthieu Sontag (worm snail).

Linnaeus’ diverse order Testacea included (from left to right, top to bottom): the West Indian green chiton (Chiton tuberculatus), the smooth gooseneck barnacle (Lepas anatifera), the common piddock (Pholas dactylus), the sand gaper (Myes arenaria, now Mya arenaria), the sheath razor (Solen vagina), the sunrise tellin (Tellina radiata), the great ribbed cockle (Cardium costatum), the abrupt wedge shell (Donax trunculus), the warty venus (Venus verrucosa), the spiny scallop (Spondylus gaederopus), the lazarus jewel box (Chama lazarus), the Noah’s Ark shell (Arca noae), the European flat oyster (Ostrea edulis), the European jingle shell (Anomia ephippium), the blue mussle (Mytilus edulis), the rough penshell (Pinna rudis), the greater argonaut (Argonauta argo), the chambered nautilus (Nautilus pompilius), the marbled cone (Conus marmoreus), the tiger cowry (Cypraea tigris), the Pacific bubble (Bulla ampulla), the music volute (Voluta musica), the common whelk (Buccinum undatum), the West Indian fighting conch (Strombus pugilis), the caltrop murex (Murex tribulus), the maculated top snail (Trochus maculatus), the tapestry turban (Turbo petholatus), the Roman snail (Helix pomatia), the bleeding tooth nerite (Nerita peloronta), Midas ear abalone (Haliotis midae), the Mediterranean limpet (Patella caerulea), the elephant tusk shell (Dentalium elephantinum), the sand worm snail (Serpula arenaria, now Thylacodes arenarius). Credits to James St. John (chiton), Ruben Vera (barnacle), Valter Jacinto (piddock), Oscar Bos [ecomare.nl] (sand gaper), Guido & Philippe Poppe [conchology.be] (razor), femorale.com (tellin, cockle, scallop, ark shell, jingle shell, bubble, fighting conch, nerite, abalone, tusk shell), Hans Hillewaert (wedge shell, venus, nautilus, whelk), Richard Parker (jewel box, marbled cone), Jan Johan ter Poorten (oyster), Wikimedia user Hectonichus (penshell, volute), Bernd Hoffmann (argonaut), Samuel Chow (cowry), Frédéric Ducarme (turban), H. Krisp (Roman snail), Wikimedia user Esculapio (limpet), Matthieu Sontag (worm snail).

6.4 Lithophyta (stone plants), composite, growing on a solid base: Tubipora (organ pipe corals), Millepora (fire corals), Madrepora (stone corals and Acetabularia algae).

Three species listed by Linnaeus under Lithophyta (from left to right): organ pipe coral (Tubipora musica), sea ginger (Millepora alcicornis), zigzag coral (Madrepora oculata). Credits to Aaron Gustafson (pipe coral), Nick Hobgood (sea ginger), NOAA, U.S.’ National Oceanic and Atmospheric Administration (zigzag coral).

Three species listed by Linnaeus under Lithophyta (from left to right): organ pipe coral (Tubipora musica), sea ginger (Millepora alcicornis), zigzag coral (Madrepora oculata). Credits to Aaron Gustafson (pipe coral), Nick Hobgood (sea ginger), NOAA, U.S.’ National Oceanic and Atmospheric Administration (zigzag coral).

6.5 Zoophyta (animal plants), growing like plants, with animated flowers: Isis (bamboo corals), Gorgonia (sea fans), Alcyonum (soft corals), Tubularia (pipe corals), Eschara (bryozoans and red algae), Corallina (coralline algae), Sertularia (bryozoans and hydrozoans), Hydra (hydras, cilliates and rotifers), Pennatula (sea pens), Taenia (tapeworms), Volvox (volvox algae and amLinebae).

Some species in Linnaeus’ order Zoophyta were (from left to right, top to bottom): the Venus sea fan (Gorgonia flabellum), the dead man’s fingers (Alcyonium digitatum), the oaten pipe hydroid (Tubullaria indivisa), the leafy bryozoan (Eschara foliacea, now Flustra foliacea), the coral weed (Corallina officinalis), the squirrel’s tail (Sertularia argentea), the grooved vorticella (Hydra convallaria, now Vorticella convallaria), the phosphorescent sea pen (Pennatula phosphorea), the pork tapeworm (Taenia solium), and the globe volvox (Volvox globator). Credits to Greg Grimes (sea fan), Bengt Littorin (dead man’s fingers), Bernard Picton (pipe hydroid, sea pen), biopix.com (bryozoan), Lovell and Libby Langstroth (coral weed), National Museums Northern Ireland (squirrel’s tail), D. J. Patterson (vorticella and volvox), Pulich Health Image Library (tapeworm).

Some species in Linnaeus’ order Zoophyta were (from left to right, top to bottom): the Venus sea fan (Gorgonia flabellum), the dead man’s fingers (Alcyonium digitatum), the oaten pipe hydroid (Tubullaria indivisa), the leafy bryozoan (Eschara foliacea, now Flustra foliacea), the coral weed (Corallina officinalis), the squirrel’s tail (Sertularia argentea), the grooved vorticella (Hydra convallaria, now Vorticella convallaria), the phosphorescent sea pen (Pennatula phosphorea), the pork tapeworm (Taenia solium), and the globe volvox (Volvox globator). Credits to Greg Grimes (sea fan), Bengt Littorin (dead man’s fingers), Bernard Picton (pipe hydroid, sea pen), biopix.com (bryozoan), Lovell and Libby Langstroth (coral weed), National Museums Northern Ireland (squirrel’s tail), D. J. Patterson (vorticella and volvox), Pulich Health Image Library (tapeworm).

Linnaeus may have made some mistakes while classifying mammals, birds, amphibians, fishes and insects, but nothing compares to the mess that his class Vermes was. It included animals from many different phyla and even red and green algae! Sometimes the same genus included both animals and plants.

And this concludes our presentation of animals in Linnaeus’ 1758 edition of Systema Naturae.

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References:

Linnaeus. 1758. Systema Naturae per Regna Tria Naturae…

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Furia infernalis, a legendary parasite

by Piter Kehoma Boll

The year was 1728. The young naturalist Carl Linnaeus was exploring some marshes in the vicinities of Lund, Sweden, in search of botanical specimens. Suddenly he was wounded by something that felt like a sudden dart hitting the skin. Linnaeus deduced that the cause was a small slender worm that buried itself deeply and quickly in the flesh, so that it was impossible to try to extract it. The wound caused such a severe inflammation that his life became endangered. He recovered, of course, but was so deeply impressed by the experience that he gave a name to the supposed animal, Furia infernalis, the fury from Hell, and introduced it in his famous Systema Naturae.

Several naturalists continued to spread the idea of such an animal and several works regarding the creature were published by very respected cientists. The animal was described as being a greyish worm of the thickness of a hair and with black extremities that inhabits marshy places and darts itself upon the exposed parts of the bodies of humans and other animals that happen to be in its reach. The torments caused by the worm after quickly burying itself in the flesh were so excruciating that they throw the victim into a state of madness and wild rage.

The Furia infernalis was supposed to look somewhat like this.

The Furia infernalis was supposed to look somewhat like this.

The idea of the existence of the creature soon became settled in people’s minds. The animal was supposed to live only in eastern Scandinavia and perhaps Russia and the Baltic contries, but did not happen further to the south nor in Norway. Even some medical treatments to cure the infection were published.

An older, wiser and more experienced Linnaeus, many years later, altered his opinion on the creature. He admitted that he possibly was drawn into error regarding the creature’s nature or even existence and considered it to be entirely fictional. However, it was too late. New cases of attacks continued to appear and the worm seemed to be a special danger to reindeer. Accounts regarding entire herds of reindeer being killed by the creature were so frequent that the purchase of animals from Sweden was entirely forbidden during the periods in which the disease was frequently reported.

Despite all the alarm, no one ever was able to present a specimen of the creature in order to validate its existence. The problem with the deer were later discovered to be caused by cestode larvae in the brain, i.e., they were afflicted by neurocysticercosis.

Today Furia infernalis is considered to be an entirely fictional animal belonging to the realm of Cryptozoology. But I wonder what had stung Linnaeus in that marsh three centuries ago.

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References:

Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae…

Brooke, A. C. 1827. On the Furia infernalis. Edinburgh New Philosophical Journal3: 39-43.

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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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