Tag Archives: systematics

New Species: September 11 to 20

by Piter Kehoma Boll

Here is a list of species described from September 11 to September 20. It certainly does not include all described species. Most information comes from the journals Mycokeys, Phytokeys, Zookeys, Phytotaxa, Zootaxa, International Journal of Systematic and Evolutionary Microbiology, and Systematic and Applied Microbiology, as well as journals restricted to certain taxa.

petrolisthes-paulayi

Petrolisthes paulayi is a new crab described in the past 10 days.

SARs

Plants

Amoebozoans

Fungi

Sponges

Cnidaria

Flatworms

Annelids

Nematodes

Arachnids

Myriapods

Crustaceans

Hexapods

Cartilaginous fishes

Ray-finned fishes

Lissamphibians

Reptiles

Mammals

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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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Filed under Algae, Systematics, Zoology

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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Filed under Cryptids, Zoology

What on Earth is Leimacopsis terricola? A flatworm mystery.

by Piter Kehoma Boll

ResearchBlogging.orgOh, ye olde times…

The 18th and 19th centuries were well marked by great worldwide expeditions by naturalists aboard ships travelling all around the world. Charles Darwin is certainly the most famous of them, but he was not the only one.

One of those naturalists was Karl Ludwig Schmarda, born in 1819. He studied in Vienna and was later a professor at the University of Graz, Austria. From 1853 to 1857, he travelled around the world investigating several locations and collecting primarily invertebrates. After his return, he published a work entitled Neue wirbellose Thiere beobachtet und gesammelt auf einer Reise um die Erde 1853 bis 1857 (New invertebrate animals observed and sampled on a travel around the Earth, 1853 to 1857).

Among the countless animals that he described, there was a worm which he called Prostheceraeus terricola. The description is as it follows:

Prostheceraeus terricola. Schmarda.
Taf. VI. Fig. 69.

Char. : Corpus oblongo-lanceolatum. Dorsum convexum viride. Fascia mediana et margo purpureus. Tentacula subuliformia.

Der Körper ist weniger flach als in andern Planarien, länglich, hinten lanzettförmig zugespitzt, vorne beinahe quer abgeschnitten. Die Fühler sind kurz und pfriemenförmig zugespitzt. Der Rücken ist stark convex, fast grasgrün, mit einer purpurrothen Längslinie nach seinem ganzen Verlaufe. Der Rand nicht wellenförmig, purpurroth gesäumt. Die Hauchfläche ist grünlichgrau. Die Länge 20mm, grösste Breite 5mm. Die Augen sind am innern Rande und der Basis der Fühler. Die Gruppe im Nacken, habe ich nicht beobachtet. Die Mundöffnung ist im vordern Drittel. Die Geschlechtsöffnungen habe ich nicht aufgefunden.
Der Grund meiner unvollständigen Kenntniss dieser Thierform ist der Umstand, dass ich nur ein Exemplar in dem obern Theile des Quindiu-Passes ober der Region der Bergpalmen gefunden hatte, welches ich in Gallego skizzirte, das aber schon zu Grunde gegangen war, als ich es in meiner Abendstation in Tocho einer wiederholten nähern Prüfung unterziehen wollte.

In English:

Oblong-lanceolate body. Green convex dorsum. Median and marginal purple stripes. Awl-like tentacles.

The body is less flat than in other planarians, elongated, behind pointed and lanceolate, front almost transversally cut. The feelers are short and awl-like pointed. The back is strongly convex, almost grass green with a purple line running fully along it. Margin not wave-like and purple-colored. The ventral surface is greenish gray. Length 20mm, largest width 5mm. The eyes are at the inner border and the base of the feelers. The group at the neck I didn’t observed. The mouth opening is in the front third. The sexual opening I did not found.
The reason of my incomplete knowledge of this animal form is due to the circumstance of finding only one specimen in the top part of the Quindiu passage above the region of the mountain palms, which I sketched it in Gallego, since it was already deteriorating, to undergo a revision back at the station in Tocho.

Here you can see the drawing of the animal:

Drawing of Prostheceraeus terricola by Schmarda, 1859

Drawing of Prostheceraeus terricola by Schmarda, 1859

Schmarda put other worms in the same genus, all of them marine. The genus is valid until today for marine species and they are classified as belonging to the Polycladida, those beautiful sea flatworms.

In fact, this animal actually looks kind of similar to a polyclad, but Schmarda found it on the top of the mountains! Quite unusual, and unfortunately he found only one single specimen.

Prostheceraeus giesbrechtii, another species described by Schmarda (1859). Photo by Parent Géry taken from commons.wikimedia.org

Prostheceraeus giesbrechtii, another species described by Schmarda (1859). Photo by Parent Géry taken from commons.wikimedia.org

Later, in 1862, K. M. Diesing made a revision of turbellarians and defined that, as the creature lived on land, it was certainly something other than a polyclad and changed it to a new genus which he called Leimacopsis (slug-like):

XVIII. LEIMACOPSIS DIESING.
Prostheceraei spec. Schmarda.

Corpus elongato-lanceolatum, supra convexum. Caput corpore continuum antice truncatum, tentaculis duobus genuinis frontalibus. Ocelli numerosi tentaculorum. Os ventrale antrorsum situm, oesophago… Apertura genitalis. . . Terrestres, Americae tropicae.

1. Leimacopsis terricola DIESING.
Corpus elongato-lanceolatum, supra convexum, viride, vitta mediana corpori aequilonga et marginibus haud undulatis purpureis, subtus viridi-cinereum. Tentacula subuliformia, brevia. Ocelli ad marginem internum et ad basim tentaculorum. Os in anteriore corporis tertia parte. Longit. 10′”, latit. 2 1/3 “.
Prostheceraeus terricola Schmarda: Neue wirbell. Th. I. 1. 30. Tab. VI. 69.
Habitaculum. In parte superiore transitus Andium Quindiu, supra regionem Palmarum montanarum (Bergpalmen), specimen unicum (Schmarda).

It’s basically a repetition of Schmarda’s description and based only on it. It looks that no other specimens were found until this time.

Years later, in 1877, H. N. Moseley published a catalogue of all land planarians known at the time. He included Leimacopsis terricola with the following description:

Family. — Leimacopsidæ, Diesing.

Genus Leimacopsis. — Diesing, Revision der Turbellarien, Abtheilung Dendrocoelen, Sitzbt. Akad. Wiss., Wien, 1861, p. 488.
Leimacopsis terricola.—Diesing, 1. c.
Prostheraceus terricola. — Schmarda, ‘Neue Wirbellose Thiere,’ Th. 1, 1—30, Tab. VI, fig. 69.
With a pair of true frontal tentacles beset with numerous eyes. Occurs high up in the Andes at the pass of Quindiu, above the region of mountain palms.

As you can see, it’s again simply a repetition of Schmarda’s description based on that single specimen from 20 years earlier, but from Diesing on, the animal started to be considered a land planarian rather than a polyclad.

Now in 1899, Ludwig von Graff published his great monography about turbellarians and I’m certain that I saw something about Leimacopsis there. Unfortunately I never found a digital copy of it and I don’t have a physical copy easily accessible either, but according to Ogren (1992), it has only a repetition of Schmarda’s account. Graff, however, changed the spelling to Limacopsis, but this is not valid according to the International Code of Zoological Nomenclature.

In 1914, finally a new article, by O. Fuhrmann, was published with information about land planarians from Colombia. He begins commenting that there were only three species known for the country by that time, one of them being Limacopsis [sic] terricola. However, the species was not found again this time…

The years passed and nothing changed. In 1991, Ogren and Kawakatsu, in part of their index to the species of land planarians, comment that several researchers, like E. M. Froehlich and L. H. Hyman, considered Leimacopsis terricola as possibly being a slug.

In 1992, Robert Ogren wrote an excellent revision of this species, which presents all information I have given here and much more. He concluded that the organism is a species inquerenda (needing further investigation) and nomen dubium (doubtful name). It is not possible to assign the animal as either a flatworm or a mollusk, or anything else due to the lack of information. Ogren considered it as “clearly part of the lore of Cryptozoology”.

As we can see, cryptids don’t need to be big animals like dinosaurs or big feet. Even a small slug-like worm from the Andes may fit.

Leimacopsis terricola is certainly an interesting organism. What was it really? Was it real? Maybe an extensive research in the area would reveal something… or not. Let’s wait and hope… Or perhaps… what about going to an adventure in Colombia’s Andean region in search of the mysterious creature?

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References:

Diesing, K. M. 1862. Revision der Turbellarien. Abtheilung: Dendrocoelen. Keiserlich-Königlichen Hof- und Staatsdruckerei DOI: 10.5962/bhl.title.2108

Fuhrmann, O. 1914. Planaires terrestres de Colombie. In: Fuhrmann & Mayor (eds.) Voyage d’Exploration Scientifique en Colombie. Mémoires de la Société des sciences naturelles de Neuchâtel, 5 (2), 748-792

Moseley, H. 1874. On the Anatomy and Histology of the Land-Planarians of Ceylon, with Some Account of Their Habits, and a Description of Two New Species, and with Notes on the Anatomy of Some European Aquatic Species. Philosophical Transactions of the Royal Society of London, 164, 105-171 DOI: 10.1098/rstl.1874.0005

Ogren, R. E. 1992. The systematic position of the cryptic land organism, Leimacopsis terricola (Schmarda, 1859)(olim Prostheceraeus)(Platyhelminthes). Journal of The Pennsylvania Academy of Science, 66 (3), 128-134

Ogren, R. E. & Kawakatsu, M. 1991. Index to the species of the family Geoplanidae (Turbellaria, Tricladida, Terricola) Part II: Caenoplaninae and Pelmatoplaninae. Bulletin of Fuji Women’s College, 29, 35-58

Schmarda, L. K. 1859. Thiere beobachtet und gesammelt auf einer Reise um die Erde 1853 bis 1857. Lepizig: W. Engelmann. DOI: 10.5962/bhl.title.14426

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Filed under Cryptids, Systematics, Zoology

Friday Fellow: Giant Tube Worm

by Piter Kehoma Boll

Giant tube worms Riftia pachyptila. Photo extrected from planeterde.de

Giant tube worms Riftia pachyptila. Photo extracted from planeterde.de

ResearchBlogging.org Let’s dive deep into the ocean and talk about this awesome animal, the giant tube worm Riftia pachyptila. Initially classified in a separate phylum, Vestimentifera, today it is included in a family of Annelids called Sibloginidae. Its common name comes from the fact that it can reach a length of 2.4 meters, quite big for a worm.

Endemic to deep-sea hydrothermal areas in the Pacific ocean, these worms are adapted to tolerate the high temperatures, pressure and levels of hydrogen sulfide in their environments. With their body protected by a chitin tube which can reach 3 meters in length, the only part exposed is a red structure, the branchial plume, highly vascularized ad rich in a hemoglobin complex of high molecular mass.

Below the plume lies the vestimentum, a muscular region which hosts the brain and the heart and is responsible for the extension and withdrawal of the plume. The name of the old phylum comprising this species, Vestimentifera, refers to this structure.

Follwing the vestimentum is the trunk and after it the opisthosome, which anchors the animal to the tube.

The plume is used to carry oxygen, carbon dioxide and sulfides into the animal’s body, which, however, lacks a mouth and gut.

A worm out of its tube. Photo extracted from spineless.ucsd.edu

A worm out of its tube. Photo extracted from spineless.ucsd.edu

To achieve nutrients, the giant tube worms host an endosymbiotic chemolithoautotrophic γ-Proteobacterium inside the trophosome, a richly vascularized organ in the trunk that constitutes a specific morphological adaptation to house the symbiotic bacteria. The sulfides are transported by the worm from the environment to the symbionts, which possess a sulfur oxidizing respiratory system and so can produce metabolic energy for themselves and for the worm.

The association between the giant tube worm and its chemoautrophic bacteria was the first of this kind to be described more than 30 years ago by Cavanaugh et al. and is currently the best studied one, but many questions about the details of this relationship, including the achievement of the bacteria by young worms, are yet to be fully answered.

Since the worm lacks a digestive system, its nutrition is entirely dependent on its symbiotic bacteria and all the anatomic adaptations designed to allow this association makes this a very good example of coevolution and make us think that there are no limits for life to adapt itself.

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References:

Lopez-Garcia, P., Gaill, F., & Moreira, D. (2002). Wide bacterial diversity associated with tubes of the vent worm Riftia pachyptila. Environmental Microbiology, 4 (4), 204-215 DOI: 10.1046/j.1462-2920.2002.00286.x

Minic, Z., & Hervé, G. 2004. Biochemical and enzymological aspects of the symbiosis between the deep-sea tubeworm Riftia pachyptila and its bacterial endosymbiont. European Journal of Biochemistry, 271 (15), 3093-3102 DOI: 10.1111/j.1432-1033.2004.04248.x

Stewart FJ, & Cavanaugh CM 2006. Symbiosis of thioautotrophic bacteria with Riftia pachyptila. Progress in molecular and subcellular biology, 41, 197-225 PMID: 16623395

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Friday Fellow: Bleeding Tooth Fungus

by Piter Kehoma Boll

Leia em português

 Our species today is a beautiful fungus, Hydnellum peckii, the bleeding tooth fungus. It was described in 1913 by Howard J. Banker and named after the botanist C. H. Peck who collected it at North Elba, New York.

Being a mushroom, its visible part is composed by its fruit bodies which can grow up to a height of 10.5 cm. When moist, these fruit bodies exude a red juice, giving the mushroom its beautiful aspect and its common name. Found through most of North America, as well as in Eurasia, it grows from the soil and it’s usually associated with conifers of the family Pinaceae, like the genera Pinus, Picea, Tsuga, Pseudotsuga and Abies.

Young specimen of Hydnellum peckii. Photo by Wikipedia user Bernypisa. Extracted from Wikipedia.

Even though it’s not poisonous, it has such a bitter taste that it turns out to be inedible. It wouldn’t be a good idea to eat it anyway, since it bioaccumulates the heavy element Cesium-137 in its mycelium.

H. peckii was revealed to have atromentin, an effective anticoagulant similar to the heparin which has also antibacterial activity against the bacteria Streptococcus pneumoniae, inhibiting an enzyme essential to their biosynthesis of fatty acids. Other uses of atromentin include an stimulant of smooth muscles and an inductor of apoptosis in leukemia U937 cells.

Not only beautiful, it is also very useful for medical and ecological purposes.

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References:

Banker, H. J. 1913. Type Studies in the Hydnaceae: V. The Genus Hydnellum. Mycologia, 5 (4), 194-205 DOI: 10.2307/3753385

Shiryaev, A. 2008. Diversity and distribution of thelephoroid fungi (Basidiomycota, Thelephorales) in the Sverdlovsk region, Russia. Folia Cryptogamica Estonica, 44, 131-141

Vinichuk, M. M.; Johanson, K. J. & Taylor, A. F. S. 2004. 137Cs in the fungal compartment of Swedish forest soils Science of The Total Environment, 323, 243-251 DOI: 10.1016/j.scitotenv.2003.10.009

Wikipedia. Hydnellum peckii. Available online at <http://en.wikipedia.org/wiki/Hydnellum_peckii>. Access on August 10, 2012.

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How are little flatworms colored? A Geoplana vaginuloides analysis

by Piter Kehoma Boll

ResearchBlogging.org As you already know, I work with land planarians, so there’s nothing more natural than seeing me talking about them. Today I’ll make a brief comment about the type species of the genus Geoplana which gives name to the family Geoplanidae (the land planarians themselves).

Geoplana vaginuloides was originally described by Charles Darwin in 1844 under the name Planaria vaginuloides. His description was based only on external morphology, which today is considered insufficient to describe correctly a land planarian. Later Stimpson (1857) moved it to his new genus Geoplana, but still only external features were used. By that time, no type species had been assigned to the genus and E. M. Froehlich (1955) decided to choose Geoplana vaginuloides (Darwin, 1844) as the type species for being the first one found by Darwin and one of the species put in the genus Geoplana by Stimpson when he described it.

It was only in 1990 that a good revision of land planarians was made by Ogren and Kawakatsu and the internal morphology, especially that of the copulatory apparatus, started to have a greater importance in describing a species correctly. Based on Geoplana vaginuloides, they defined the genus Geoplana as follows:

“Geoplanidae of elongate body form; creeping sole broader than a third of the body width; strong cutaneous longitudinal muscles; mc:h value from 4%-8%; parenchymal longitudinal musculature weak or absent, not in a ring zone; testes are dorsal; penis papilla present; female canal enters genital antrum dorsally; cephalic glandulo-muscular organs, sensory papillae and adenodactyls absent.” (Ogren & Kawakatsu, 1990).

As noticed by Riester (1938), G. vaginuloides possesses a very long penis papilla invading the female antrum, as well as other peculiar features. These aspects were important to consider a land planarian found by Marcus in 1951 as belonging to this species, even though it had external colors almost inverted when compared to the specimen described by Darwin.

Using the internal morphology to assure that all the following descriptions of land planarians belong to a single species, Geoplana vaginuloides, we can find at least 4 different external color patterns to this species:

  •  Darwin 1844:  “Ocelli numerous, placed at regular intervals on the anterior extremity; irregularly, round the edges of the foot. […] Sides of the foot coloured dirty “orpiment orange”; above, with two stripes on each side of pale “primrose-yellow,” edged externally with black; on centre of the back a stripe of glossy black; these stripes become narrow towards both extremities.”
    Locality: Rio de Janeiro, Brazil
  •  Riester, 1938: “Unterseite und Körperänder weinrot, dann zwei schmale gelbe Streifen und in der Rückenmitte ein tief Schwarz glänzendes breites Band.” (Underside and body edges wine red, then two narrow yellow stripes and in the middle of the back a deep black shiny broad band.)
    Locality: Teresópolis/Guapimirim, Rio de Janeiro, Brazil
  • Marcus, 1951: “A faixa mediana é ocre, na maior parte da extensão. Anterior e posteriormente é preta. Flanqueiam-na faixas amarelas claras, cada uma tão larga quão a mediana. As zonas dorso-laterais são pretas com pontinhos claros, que não são olhos. O ventre é claro.” (The median band is ochre in most of its length. Anteriorly and posteriorly it’s black. Light yellow bands flank it, each one as broad as the median one. The dorsolateral zones are black with white spots, which aren’t eyes. The venter is light.)
    Locality: Eldorado, São Paulo, Brazil
  • C. G. Froehlich, 1958: “The colour pattern is similar to type C of Marcus (1952, pp. 76-77, pl. 23 fig. 136) but the median reddish stripe is broader (about 1 mm. across, just in front of the pharynx), and both the black and the white stripes that follow on each side are narrower (about 0.2 to 0.3 mm broad each, in the same region). The median stripe begins at 2.5 mm from the anterior tip. The creeping sole is greyish white.”
    Locality: Itanhaém, São Paulo, Brazil

Different color patterns in Geoplana vaginuloides according do Darwin, 1844 (1), Riester, 1938 (2), Marcus, 1951 (3) and C. G. Froehlich, 1958 (4)

Location of the 4 morphotypes seen in the picture above. Image made on Google Earth.

Along with those descriptions, Prudhoe (1949), found an animal in Trinidad with the same external description given by Darwin, but its internal structure was very different from Riester (1938). So it was probably a different species.

About photographs of this species, I found only the three seen below. They all belong to specimens with a color pattern close to those described by Marcus and Froehlich. It would be interesting to find an animal with the color pattern from the original description by Darwin!

Geoplana vaginuloides (Darwin, 1844). Photo by Fernando Carbayo. Extracted from each.uspnet.usp.br/planarias/

Geoplana vaginuloides (Darwin, 1844). Photo by Fernando Carbayo. Extracted from each.uspnet.usp.br/planarias/

Geoplana vaginuloides (Darwin, 1844). Notice that this one doesn’t have the black border flanking the median orange band. Photo by Instituto Rã-Bugio. Extracted from http://www.ra-bugio.org.br

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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, Annales des Sciences Naturelles, 14, 241-251

Froehlich, E. M. 1955. Sobre Espécies Brasileiras do Gênero Geoplana. Boletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Série Zoologia, 19, 289-339

Froehlich, C. G. 1958. On a Collection of Brazilian Land Planarians. Boletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Série Zoologia, 21, 93-121

Marcus, E. 1951. Turbellaria Brasileiros. Boletim da Faculdade de Filosofia, Ciências e Letras da Universidade de São Paulo, Série Zoologia, 16, 5-215

Ogren, R. E. & 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

Prudhoe, S. 1949. Some roundworms and flatworms from the West Indies and Surinam. – IV. Land Planarians. Journal of the Linnean Society of London, Zoology, 41 (281), 420-433 DOI: 10.1111/j.1096-3642.1940.tb02415.x

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

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 Philadelphia, 19-31

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What’s a species 2: Vertical species concepts

by Piter Kehoma Boll

Leia em português

Hello, guys!

I finally decided to go on and write the second part of my article about species concepts. You can see the first part here, where I talked about horizontal species concepts. Today I’m going to talk about the other perspective, the vertical species concepts, which are based on lineages, i.e., how species happen through time.

Vertical concepts are hardly used to actually define a species, since they do not represent the current situation of living beings and it’s hard to know the real history of a population to determine its status through all his existence. However these concepts are useful in phylogenetic reconstructions and to understand how new species arrive from others through time.

Well, let’s see the two main vertical species concepts.

1. Cladistic species concept

Proposed by Ridley in 1989, it defines a species as a set of organisms between two speciation events, or between one speciation event and one extinction event. According to this, a species comes to exist when a lineage of organisms is split in two. There are no paraphyletic species in this concept, since when a speciation event occur, the ancestral species becomes extinct, giving rise to two new species.

Cladistic concept: every time a speciation event occur, two new species are created and the ancestral species becomes extinct.

2. Evolutionary species concept

An evolutionary species is defined as a set of organisms from a single lineage that has its own evolutionary tendencies and historical fate. Differently from the cladistic species, the evolutionary species does not necessarily become extinct when another lineage split from it, so being able to be paraphyletic, i.e., if a population is divided in two, the one that continues to have the same general features and the same evolutionary path is considered the same species as the ancestral one.

Evolutionary concept: a species does not necessarily become extinct during a speciation event. Species 1 is paraphyletic after split from species 2.

Since there is no record of the evolutionary history of organisms, there is no way to determine it for any species. Some ideas may be proposed and highly supported by genetic analyses, but we can never know for sure how things really happened, so that vertical concepts cannot be applied practically and are more useful to infer genetic relationships between different populations and so guide their correct management in conservation efforts.

Another point is that by vertical concepts, two organisms are considered separate species as soon as they move on in different lineages, in different populations that will not come in touch again, so that even two cousins would be different species, even though genetically, morphologically and ecologically very similar.

So vertical concepts are more useful to determine phylogeny and help in population genetics, but not to actually define species in any ecosystem, since in this case the situation is characterized by the present status of organisms and so better supported by horizontal approaches.

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References:

Mayden, R. L. 1997. A hierarchy of species concepts: the denoument in the saga of the species problem, in M. F. Claridge, H. A. Dawah and M. R. Wilson (eds.), Species: The units of diversity, London: Chapman and Hall, 381-423

Ridley, M. 2004. Evolution. Blackwell Publishing. ISBN 1-4051-0345-0.

Stamos, D. N. 2002. Species, languages, and the horizontal/vertical distinction. Biology and Phylosophy, 17, 171-198.

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What’s a species 1: Horizontal species concepts

by Piter Kehoma Boll

Leia em português

What’s a species?

Maybe to you that may sound like something too obvious to think about, but actually the concept of species is one of the most intriguing and controversial topics in biology. Sometimes it’s not so easy to distinguish one species from another and that may lead to problems in several fields of biology, including not only systematics, but also ecology, conservation and evolution.

Many times, of course, two individuals can easily be recognized as different species. Nobody would doubt that a giraffe and a banana tree belong to different species, right?

A giraffe and a banana tree, surely not a couple. Pictures by Anna Cervova and Andrew Schmidt.

Now look at these two butterflies. Are they different species?

Two very similar butterflies, Danaus erippus (left) and D. plexippus (right). Photos by Gabriela ruellan* (flickr.com/people/56823778@N00) and David Wagner.

As you can see now, sometimes it’s not so easy to say if a group of individuals forms one or more species.

Trying to solve this problem, many concepts of what’s a species have arisen through the decades. As far as 22 concepts were elaborated, trying to cover all kind of situations related to species differentiation. Those concepts can be divided in two different approaches of the problem: horizontal and vertical. When analyzing species in a horizontal way, we look at them how they are in the present, comparing the populations in the way they look like, behave and are distributed. On the other hand, a vertical approach considers how species happen through time, putting priority on historical and evolutionary aspects.

Here I’ll make a quick review of the three main horizontal species concepts, which are the most practically used as we try to define what a species is.

1. Biological species concept

Probably the best known concept and the most highly applied. It defines a species as a set of organisms where individuals recognize one another and seek each other for mating, so maintaining the intercommunication of their genes. A biological species is isolated from other species by intrinsic or extrinsic features that prevent interbreeding.

In other words, a biological species is a set of organisms able to interbreed and have fertile offspring. A classic example of two biological species is the horse Equus ferus caballus and the donkey Equus africanus asinus which can breed to produce a mule, but that’s sterile.

A mare, Equus ferus caballus (left), a donkey, Equus africanus asinus (right) and a mule (center). Photos by ‘Little Miss Muffit’* (flickr.com/people/42562654@N00)(mare), Adrian Pingstone (donkey) and Dario Urruty (mule).

Even though this concept applies well to most plants and animals, it doesn’t fit to bacteria and other microorganisms that reproduce only asexually.  Despite that, some plant species can easily form fertile hybrids between distinct species. Orchids are champions on that, with lots of hybrids species arising from crossing species of the genus Cattleya.

Cattleya forbesii (left), C. guttata (right) and their hybrid, Cattleya x dayana (center). That’s a naturally occurring fertile hybrid. Photos by Dr. Volkmar Rudolf (C. forbesii), Wikimedia Commons’ User Orchi (commons.wikimedia.org/wiki/User:Orchi)(C. guttata) and Adilson A. Filho (www.flickr.com/people/adilsfilho/)(C. x dayana).

2. Ecological Species Concept

An ecological species is a set of organisms belonging to a single or closely related lineages that basically occupy the same niche in an ecosystem, i.e., have the same habitat and the same habits and needs for physical resources and conditions to survive.

Due to the fact that different species use ecological resources differently, they use to become divergent in aspect, behavior and location, so leading to isolating from one another. Maybe they would be able to interbreed, but it doesn’t use to happen because of their different locations or time of mating.

Two species of giant roundworms, Ascaris lumbricoides and A. suum, are very closely related and similar in shape, but the first is a parasite of humans and the latter a parasite of pigs, so that they are isolated from each other for using different habitats.

Pictures of Ascaris lumbricoides and A. suum. Almost identical, but living in different hosts. Pictures by the Centers for Disease Control and Prevention, U.S. federal government and by nematodes.org, respectively.

Another example are the grizzly bear Ursus arctos and the polar bear Ursus maritimus. Even though living in different habitats and having different behaviors, including the fact that the grizzly tends to mate on land while the polar mates in the water, several hybrids have been reported, including wild ones, and they are fertile, so that by the biological concept, they would belong to a single species, even though by ecological aspects they are quite different ones.

Taxidermied “prizzly bear”, a polar-grizzly bear hybrid, at Rothschild Museum, Tring, England. Picture by Sarah Hartwell*, extracted from wikipedia.

3. Phenetic species concept

This concept defines basically that a species is a set of organisms that look similar enough, i.e., similarity is the primary criterion for defining a species. Different from the two previous concepts, this one simply considers that species exists, but doesn’t justify how they came to be so.

Despite of its apparent inaccuracy to define natural species, it’s actually the primary method used to differentiate species. When a new species is described, it is usually so defined by comparing it to species already known, highlighting morphological and behavioral aspects.

Two beautiful species of macaw, the blue-and-yellow macaw Ara ararauna and the scarlet macaw Ara macao, are quite different in coloration, so considered different species. Their habitats overlap in nature, but they do not produce hybrids except in captivity, and those are not fertile.

Blue-and-yellow macaw, Ara ararauna (left), Scarlet macaw, Ara macao (right) and their sterile hybrid Catalina macaw (center). Photos by Wikimedia Commons’ user Fiorellino* (A. ararauna), Matthew Romack* (www.flickr.com/people/stoichiometry/) (A. macao) and Wikimedia Common’s user Arkansas Lad* (catalina macaw).

However, this concept doesn’t work many times. A typical example is when considering two fruit fly species, Drosophila persimilis and D. pseudoobscura. They look almost identical to each other, but when put together, they never breed, so indicating that they actually do not belong to the same species.

Two different species that look almost identical, Drosophila persimilis (left) and D. pseudoobscura (right). Photos by BIO Photography Group*, Biodiversity Institute of Ontario, extracted from boldsystems.org

I hope that now you are starting to see why is not so easy to tell where one species begins and the other ends. Perhaps there is no such thing as a species after all, at least not like we think about it.

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* These images are licensed under Creative Commons license, hold by their respective owners.

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References:

Mayden, R. L. 1997. A hierarchy of species concepts: the denoument in the saga of the species problem, in M. F. Claridge, H. A. Dawah and M. R. Wilson (eds.), Species: The units of diversity, London: Chapman and Hall, 381-423

Ridley, M. 2004. Evolution. Blackwell Publishing. ISBN 1-4051-0345-0.

Smith, D., Lushai, G., & Allen, J. 2005. A classification of Danaus butterflies (Lepidoptera: Nymphalidae) based upon data from morphology and DNA Zoological Journal of the Linnean Society, 144 (2), 191-212 DOI: 10.1111/j.1096-3642.2005.00169.x

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A Brief History of the Kingdoms of Life

by Piter Kehoma Boll

Since ancient times, living beings were classified as either plants or animals and Linnaeus retained this system in his great work Systema Naturae in the 18thcentury, where he divided nature into three kingdoms: Regnum Animale (animal kingdom), Regnum Vegetabile (plant kingdom) and Regnum Lapideum (mineral kingdom). This system was not intended to reflect natural relationships among living organisms since Linnaeus was a Christian and believed that all life forms were created separately by God himself just as they are today, but was created to make the study of living beings easier.

Linnaeus and the two kingdoms of life. Painting by Alexander Roslin, 1775.

When the first unicellular organisms were discovered by Antoine van Leeuwenhoek in 1674, they were placed in one of the two kingdoms of living beings, according to their characteristics. It remained so until 1866, when Ernst Haeckel proposed a third kingdom of life, which he called Protista, and included all unicellular organisms in it.

Haeckel and the three kingdoms. Photo by the Linnean Society, 1908.

Later, the development of optic and electronic microscopy showed important differences in cells, mainly according to the presence or absence of a distinct nucleus, leading Édouard Chatton to distinguish organisms in prokaryotes (without a distinct nucleus) and eukaryotes (with a distinct nucleus) in a paper from 1925. Based on it, Copeland proposed a four-kingdom system, moving prokaryotic organisms, bacteria and “blue-green algae”, into the kingdom Monera. The idea of a ranking above kingdom came from this time and so life was separated into two empires or superkingdoms, Prokaryota (Monera) and Eukaryota (Protista, Plantae, Animalia).

Two empires and four kingdoms

Since Haeckel, the position of fungi was not well established, oscillating between kingdoms Protista and Plantae. So, in 1969, Robert Whittaker proposed a fifth kingdom to include them, the called Kingdom Fungi. This five-kingdom system remained constant for some time; Monera were prokaryotes; Plantae were multicellular autotrophs (producers); Animalia multicellular consumers; and Fungi multicellular saprotrophs (decomposers). Protista was like the trash bag, where anything that doesn’t fit in the other 4 kingdoms was placed in.

Whittaker and the five kingdoms. Photography source: National Academy of Sciences: Robert H. Whittaker (1920—1980) – A Biographical Memoir by Walter E. Westman, Robert K. Peet and Gene E. Likens.

With the dawn of molecular studies around 1970, significant differences were found inside the Prokaryotes, regarded, for example, to the cell membrane structure. Based on those studies, Carl Woese divided Prokaryota in Eubacteria and Archaeobacteria, emphasizing that the differences between those two were as high as the ones between them and the eukaryotes. This later gave rise to a new higher classification of life in three domains, Bacteria, Archaea and Eukarya.

Woese and the three domains. Photo from Photo from News Bureau – University of Illinois, given by IGB (Institute for Genomic Biology).

By the end of the 20th century, Thomas Cavalier-Smith, after intense study of protists, created a new model with 6 kingdoms. Bacteria and Archaea were put together in the same kingdom, called Bacteria. Protists were divided in two kingdoms: (1) Chromista, including Alveolates (Apicomplexa, parasitic protozoa like Plasmodium; Ciliates and Dinoflagellates), Heterokonts or Stramenopiles (brown algae, golden algae, diatoms, water moulds, etc) and Rhizarians (like Radiolaria and Foraminifera), among others; and (2) Protozoa, including Amoebozoa (amoebas and slime moulds), Choanozoa (choanoflagellates) and a set of flagellated protozoa called Excavata. Glaucophytes, red and green algae were classified inside the kingdom Plantae.

Cavalier-Smith and his two new kingdoms. Photo from Department of Zoology – University of Oxford.

From the 21st century on, a phylogenetic approach to classify living beings has gained strength. After a lot of molecular analyses using different genes, the real evolutionary relationship among Eukaryotes is still not clear. However, the following groups are supported by most phylogenetic trees:

(1) Archaeoplastida (or Plantae): glaucophytes (Glaucophyta), red algae (Rhodophyta) and green plants and algae (Viridiplantae)

(2) Chromalveolata: Stramenopiles or Heterokonta, haptophytes (Haptophyta), cryptomonads (Cryptophyta) and Alveolata.

(3) Rhizaria: Foraminifera, Radiolaria and some amoeboid protozoa

(4) Amoebozoa: amoebas and slime molds

(5) Opisthokonta: animals, fungi, choanoflagellates

(6) Excavata: many flagellate protozoa. This group, however, isn’t as well supported as the other ones.

The current (maybe not so) well-established groups of organisms

So, as we can see, the Eukaryotes’ case is yet to be solved, but we hope that further molecular studies will help us understand better how the tree of life branches.

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References:

Baldauf, S. L. et al. 2000: A Kingdom-Level Phylogeny of Eukaryotes Based on Combined Protein Data. Science 290, 972-977.

Cavalier-Smith, T. 2004: Only six kingdoms of life. Proceedings of the Royal Society B 271, 1275-1262.

Rogozin, I. B. et al. 2009: Analysis of Rare Genomic Changes Does Not Support the Unikont–Bikont Phylogeny and Suggests Cyanobacterial Symbiosis as the Point of Primary Radiation of Eukaryotes. Genome, Biology and Evolution 1, 99-113.

Wikipedia. Kingdom (Biology). Available online at: <en.wikipedia.org/wiki/Kingdom_(biology)>. Access on December 5th, 2011.

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