Parasitism, symbiosis and comensualism came up in my recent write up on (paen to) ivermectin,
www.dailykos.com/…
and made me think of lichens, which are an interesting example of the later two.
First of all, you are an example of very old evolved symbiosis. The organelles (mitochondria and chloroplasts if you be a green thumb) within your cells were once free living bacteria and still have their own genome, distinct from yours.
They were ingested by other prokaryotes, came to live inside them and perform essential functions. Now we can't live without each other and have no independent existence. Thus the eukaryote was born!
In a lichen, two eukaryotes (an algae or cyanobacteria & a fungi)
which have little structure alone, come together to form manifold and varied structures that can be more successful than either organism alone which are limited mainly to films, blobs or fibers.
"It is estimated that 6–8% of Earth's land surface is covered by lichens.There are about 20,000 known species.Some lichens have lost the ability to reproduce sexually, yet continue to speciate.They can be seen as being relatively self-contained miniature ecosystems, where the fungi, algae, or cyanobacteria have the potential to engage withother microorganisms in a functioning system that may evolve as an even more complex composite organism. Lichens may be long-lived, with some considered to be among the oldest living things." Wikipedia
Here it is crustose, and taking its time to eat a boulder! Perhaps a masonry building for dessert, monsieur?
Here is a somewhat slovenly jelly lichen.
The fungi and algae can and do live independently but in less harsh environments. They can be separated, live thus and then recombined. The structures they form are specific enough to get their own latin names as species. Isn't that cool?
The fungus does alot of the heavy lifting here. It gets sweet sweet simple carbs from its photosynthesic partner, but provides the structural home, dissolved rock minerals and much of the needed moisture retention.
Fungi have a similar relationship with earths chief glory, her forests and trees. The latter grow many times as fast with mycorizial fungi. The trees can even swap food to others through hyphae. Thus the otherwise puzzling living stumps. allabouttrees.com/... So, Green Communism in the woods!
"Two forms of reproduction can be found amongst living organisms - sexual and asexual. It is by the mixing of genes from two individuals, via sexual reproduction, that genetic diversity is effected, whereas in asexual reproduction there is no such mixing of genes. Both sexual and asexual reproduction can be found amongst the lichens. When talking of plants (or lichens, which were once thought of as plants) asexual reproduction is commonly called vegetative reproduction. Though lichens, as a whole, may reproduce both sexually or vegetatively, there are species in which both types of reproduction may be common but also species where one type is rare or even unknown. In each form of reproduction propagules of some sort are produced and dispersed and there is a separate page dealing with PROPAGULE DISPERSAL. The SEXUAL VS. VEGETATIVE page gives some general comments about the two means of reproduction.
When talking about lichen reproduction two fundamental questions arise:
What does it mean to talk of sexual reproduction in lichens?
What is an individual lichen?" From aussie site in sources
They have great economic impact makings soils (I first typoed "souls" which almost works) and enriching them with solubilized minerals. They feed delicious caribou and reindeer as well as people in an emergency.
Indeed many are used culinarily:
"In the past, Iceland moss (Cetraria islandica) was an important source of food for humans in northern Europe, and was cooked as a bread, porridge, pudding, soup, or salad. Bryoria fremontii (edible horsehair lichen) was an important food in parts of North America, where it was usually pitcooked. Northern peoples in North America and Siberia traditionally eat the partially digested reindeer lichen
(Cladina spp.) after they remove it from the rumen of caribou or reindeer that have been killed. Rock tripe (Umbilicaria spp. and Lasalia spp.) is a lichen that has frequently been used as an emergency food in North America, and one species, Umbilicaria esculenta, (iwatake in Japanese) is used in a variety of traditional Korean and Japanese foods." Wiki.
Kal Paasi spice
Yum, rumen. Have to think about, ruminate on that. It has a bit of protein and some carbs (as not very digestable polysaccharides) but not a lot of calories.
"Two obstacles are often encountered when eating lichens: lichen polysaccharides are generally indigestible to humans, and lichens usually contain mildly toxic secondary compounds that should be removed before eating. Very few lichens are poisonous, but those high in vulpinic acid or usnic acid are toxic. Most poisonous lichens are yellow." Wiki
They have been used as packing material and dyestuffs.
Fire starter and decorations.
A lot of possible applications are being researched in bioremediation, to break down wasted and they provide us with a great reason not to sit still for decades.
"Lichenometry" can date objects or places via assumed growth rates. Not precise but better than nothing. It also gives short term dates, unlike 14C dating.
In short, they are awesome and add to the wonder of our amazing planet. That said, I'm lichen me some ahahaha.
Sources and pictures from: namyco.org/…
en.m.wikipedia.org/…
www.anbg.gov.au/...