Las plantas que revivieron después de 400 años

ORIGINAL: BBC
BBC Mundo
28 de mayo de 2013

Foto: Catherine La Farge

Los glaciares en esta región se han estado desvaneciendo aceleradamente desde 2004, a un ritmo de unos tres o cuatro metros al año.

Un equipo científico observó cómo unas plantas que quedaron congeladas bajo un glaciar durante la llamada Pequeña Edad de Hielo, hace siglos, volvieron a germinar.

Muestras de plantas de 400 años de antigüedad brotaron de nuevo en condiciones de laboratorio.

Según los investigadores de la Universidad de Alberta, en Canadá, esta "resurrección" es significativa para entender cómo se recuperan los ecosistemas del planeta tras los ciclos periódicos de temperaturas heladas.

Los resultados del estudio fueron publicados en la revista científica Proceedings of the National Academy of Sciences. 

La Pequeña Edad de Hielo fue un período frío que abarcó aproximadamente de 1550 a 1850, y puso fin a una era calurosa llamada "óptimo climático medieval".

Musgos latentes bajo el glaciar

El equipo científico exploraba la zona en torno del glaciar Teardrop, en el Paso de Sverdrup, en lo alto del ártico canadiense, cuando notó un inusual manto de vegetación.

"Caminábamos por el borde del glaciar cuando vimos estas grandes colonias saliendo de debajo del glaciar, que tenían un tinte verdoso", describió Catherine La Farge, la investigadora líder del estudio.

"Los glaciares están desapareciendo realmente rápido y van a exponer toda esta vegetación terrestre, y eso va a tener un gran impacto"

Catherine La Farge, Universidad de Alberta

Los glaciares en esta región se han estado desvaneciendo aceleradamente desde 2004, a un ritmo de unos tres o cuatro metros al año.

Ese proceso está dejando a la vista terrenos que no han visto la luz del día desde la Pequeña Edad de Hielo.

Las plantas observadas, conocidas como briofitas, son plantas terrestres no vasculares, como los musgos. Carecen de tejidos vasculares que hacen bombear los fluidos por las distinatas partes del organismo.

Estas plantas pueden sobrevivir a los duros inviernos del Ártico completamente disecadas, volviendo a germinar cuando suben las temperaturas.

Pero lo que sorprendió a la doctora La Farge fue le garminación de briofitas que permanecieron bajo el hielo durante tanto tiempo.

Nuevas especies

El retroceso Glaciar Teardrop ha revelado la existencia de nuevas especies.

"Cuando las trajimos al laboratorio y las observamos en detalle pude ver que de algunos de los tallos habían brotado nuevas ramas laterales verdes y esto me dio a entender que estos especímenes se están regenerando sobre el terreno. Eso me dejó atónita", explicó La Farge.

"En un paisaje cubierto por capas de hielo, siempre hemos pensado que las plantas vienen de algún refugio en los márgenes del sistema de hielo, nunca consideramos que las plantas terrestres podrían venir de debajo de un glaciar", declaró.

El retroceso del glaciar Teardrop está poniendo al descubierto una gran variedad de biodiversidad, que incluye cianobacterias, bacterias capaces de realizar fotosíntesis oxigénica, y algas verdes terrestres. Muchas de las especies observadas son totalmente nuevas para la ciencia.

"Es todo un mundo nuevo que está emergiendo de debajo de los glaciares que realmente debe ser estudiado", dijo La Farge.

"Los glaciares están desapareciendo realmente rápido y van a exponer toda esta vegetación terrestre, y eso va a tener un gran impacto", añadió.

Killer Canadian coelacanth discovered

ORIGINAL: CosmosMagazine

The fast-swimming coelacanth Rebellatrix chasing smaller species of fishes in the Early Triassic ocean west of Pangaea. Credit: Artwork by Michael Skrepnick.

LONDON: Canadian scientists have discovered a fossilised ‘rebel’ coelacanth fish with an unusual body shape that suggests it was a fast-swimming predator.

The finding suggests that contrary to popular belief, coelacanths, the so-called ‘living fossils’, have undergone significant morphological change during their history.

“Rebellatrix divaricerca, most importantly, shatters the commonly held notion that coelacanths were an evolutionarily stagnant group,” said Andrew Wendruff from University of Alberta, in Edmonton, one of the researchers who discovered the fossil and lead author of the paper published in the Journal of Vertebrate Palaeontology.

Dramatically different to other coelacanth

The largest specimen of Rebellatrix, though partial, shows that it grew upwards of 1 meter in length. Credit: Photograph and drawing by A. Wendruff

“Rebellatrix is dramatically different from any coelacanth previously known, and thus had undergone significant evolutionary change in its ancestry,” he said.

Until the 1930s coelacanths were thought to have been extinct since the Late Cretaceous period, around 70 million years ago, when dinosaurs were still alive on Earth.

However, in 1938 a fisherman in Africa caught a living coelacanth. The most striking thing about the newly discovered fish was that their body plan differed very little from ancient fossil specimens resulting in the fish being referred to as ‘living fossils’.

Rebel without a cause

The modern coelacanth, Latimeria chalumnae, and most of the fossil specimens discovered to date have broad, flexible tails suitable for moving at slow speeds and lying in wait for prey.

In contrast, “the forked tail of Rebellatrix indicated that it was a fast-moving, aggressive predator,” said Wendruff.

“Rebellatrix was able to search actively for the fishes that it preyed upon and catch them at high speed,” added Mark Wilson, co-author of the study and fellow University of Alberta researcher.

Wendruff and Wilson found the R. divaricerca fossil in the Lower Triassic Sulphur Mountain Formation near Tumbler Ridge in the Rocky Mountains in British Columbia, Canada.

It is thought to be from the Early Triassic period, approximately 250 million years ago. The closest coelacanth fossil in age is known as Alenypterus. It dates from the Mississippian period and is at least 70 million years older. It also has a very different body plan that is more similar to that of living coelacanths than that of Rebellatrix.

Prior to findings such as Rebellatrix, scientists believed that coelacanths have changed little over time, but this now seems unlikely.

“The similar body forms are not a result of close relationships,” said Wendruff. “Nature is constantly recycling ideas, body forms and structures. This is referred to as convergent evolution. Many times there is one particular form that is most efficient for a particular function.”

When asked about why Rebellatrix evolved such a different body shape to other members of the coelacanth family, Wendruff suggested that as the mass extinction event that happened just before the beginning of the Triassic period wiped out 90% of marine life Rebellatrix could have evolved to fill a newly vacant predator ‘niche’ in the marine ecosystem.

Forked tail before it's time

“Large predators seem to be particularly vulnerable during such intervals, so this extinction might have 'opened the door' for coelacanths to explore new functional roles,” said palaeobiologist and coelacanth expert Matt Friedman from the University of Oxford in the UK.

The newly evolved body form was not successful, however, because “while other fork-tailed fishes appear later in the fossil record, Rebellatrix and its descendants are noticeably absent. This leads us to believe that Rebellatrix was a dead end in the evolution of cruising predation,” said Wendruff.

Friedman said: “this discovery adds to a growing view that coelacanth evolution was more nuanced than textbook portrayals would suggest.”

He added: “It is the latest in a series of finds over the past decade or so that have shown coelacanths didn't just have a static evolutionary history when it came to body form. Rebellatrix, with its unusual tail fin and body proportions, can be added to other anatomical 'experiments' in coelacanth history, including eel- and leaf-shaped forms.”

Wendruff believes that other unique forms of coelacanth have yet to be found and that “in the future they will have many more surprises in store.”