Tuesday, May 17, 2011

The Slug-Snail and Hymenophyllum tunbrigense, two links in evolution

I woke up early to go walking along the Pijaral Trail in the Parque Rural de Anaga, in the far north of the island of Tenerife, which leads to the impressive Roque de Anambro. My greatest motivation to tour it was to find and see for the first time in my life one of the most primitive ferns Planet, Hymenophyllum tunbrigense. This tiny and transparent fern, halfway between a moss and fern, was for me an unresolved for many years.

The trail was wet, slippery and gloom, completely covered by the thick canopy of endemic tree heather, Erica platycodon, which let in only a small ray of light. I had the feeling of walking through a tunnel plant. It was cold and the air was saturated with moisture, because the entire park was covered by a thick fog in continuous movement that rose rapidly from the sea, collided with the tops of the trees and shrubs of laurel forest that covers the entire Massif Anaga, was entering through the leaves and branches and their passage was spray impregnated with everything he touched. And condensed into fresh water from a high purity, falling drop by drop upon the volcanic soil to form small ponds and a creek. I was fully immersed in Macaronesian horizontal rain phenomenon.

Not to slip and dodge the puddles was looking under his feet, which prevented me from noticing the stems of heather, Hymenophyllum preferred habitat. Soon afterwards I felt slightly dizzy as my eyes went from my feet to the trunks of each side and again to my feet, hundreds of times, all spiced by high humidity, low light and the cold wind that I was in the left side of the face. In one of my steps I had to give a little jump to avoid stepping on a black critters. I bent down to see them better and my surprise was great. Hybrids appeared to slug and snail, ie slugs with a snail shell under the skin of his abdomen. Uauuuu, interesting little creatures, I thought. And of course I took my camera to take them as souvenirs.

In the Visitor Center Parque Rural de Anaga I told one of the technicians on this slug-snail and immediately he knew I was talking about the endemic Plutonia lamarckii. They even have a large poster of endemic invertebrates where it leaves a picture of this little animal. Double click on the photo for appreciate better the details.

 The Plutonia lamarckii is a link in evolution, an intermediate step between a slug and a snail, which has been left half way and continues unchanged for millions of years. You may need a few million more years to take the next step and become a spiral outer shell. Certainly remains unchanged simply because it feels very comfortable as it is, is perfectly adapted to the laurel forests and has no need to change your body. Any environmental circumstance forces him at all. Living things evolve only forced by changes in their habitat. This is the famous Darwinian principle: Either you adapt or you die and disappear from the face of the Earth. The habitat of the snail-shell Canary has not changed in millions of years. No need to evolve. And is perfectly adapted to its environment.

As it grows, the shell that protects your digestive system and other vital organs, the skin of the abdomen begins to crumble, revealing part of the calcium carbonate shell.

 In this other Plutonia lamarckii is best seen spiraling shell. Its tentacles and eyes are typically snail. View and photograph this evolutionary link I am delighted, as much as the tiny ferns that I expected a few meters above the moss that covered an old heather.

 Several fronds of about 3 or 4 inches of Hymenophyllum tunbrigense. Is striking transparency. It seems that the fern and moss have evolved together, as all copies of Hymenophyllum moss growing on it, which is not what is left but a more sparse, that lives attached to the bark of Erica platycodon. This fern can live on dripping rocks and bleak with the condition that it be lined with moss symbiont.

His name is composed of two Greek words together: Hymen = hymen membrane and phyllon = leaf, or plant with thin leaves as hymen membrane and a Latinized English word, tunbrigense, ie, Tunbridge Wells, City Kent, southeast England, for being the place where it was first described.

Hymenophyllum tunbrigense colony, sometimes consisting of hundreds of fronds, all united by a long, branched rhizome that grows very thin layer embedded in moss, glued to turn on the cracked bark of tree heather. The condensed water on the tops of the trees down the bark, moisten the moss layer which acts like a sponge and so the rhizome of Hymenophyllum obtained permanent moisture it needs.

Some sori crowded fronds produce spores. This photo shows the moisture soaks the frond. The ferns, like the slug, snail, is another intermediate link in evolution. His appearance, size and transparency in him little different from a moss, such as Fissidens asplenioides, with which is very similar. They live in very damp and gloomy.

Several fronds of the moss Fissidens asplenioides photographed in a very dark dripping rock on the island of Faial in the Azores Archipelago. It is surprising resemblance to the Hymenophyllum tunbrigense.

When Hymenophyllum spores are mature, the leaflets of the sori are opened and the wind helped disperse. If they are lucky and fall on the moss symbiont, whether covering the bark of a dripping rock heather, germinate and re-start their life cycle.

 Striking and majestic Roque de Anambro of 815 m. high at the top of the trail along the Pijaral. One has the impression of looking at a giant. His vision is not suitable for rapid, since at this point the trail is very narrow, to the left is a deep vertical cliff that ends in the sea, all of it covered by trees of laurel and right a thick forest with a steep slope. It's like balancing on a knife edge of rock, whose tip is the Roque. His image is an unforgetable memory.

No comments:

Post a Comment