Lichen with cyanobacteria
|[Note Guidelines] Photographer's Note [French]|
I observed this lichen in the woods of Rieucoulomb, a few miles northeast of Prades le Lez, in the department of Herault.
It is a green lichen. The photograph shows the thallus of the lichen which is thick and rigid.
It is a foliose type thallus with very little adhesion to substrates, which is the litter from the undergrowth: this is an humus lichen.
It owes its green color to the symbiotic association with green algae. The underside of the thallus is tomentose, light brown.
You can notice in the center and at the periphery of the thallus, dark clusters, almost black: these are the cephalodia, from a second symbiosis with a cyanobacterium.
We are therefore in relatively uncommon cases of a symbiosis with three partners: the fungus (mycosymbiote), green alga (phycosymbiote) and bacteria (cyanosymbiote).
The fungus shows only rarely apothecia (here you can not observe any of them).
It is quite difficult for an amateur to determine the names of lichens. However, it seems to me that it is Lobaria amplissima (Scop.) Forssell, 1883.
But I'm not absolutely certain. Any assistance in the determination will be welcome.
The photograph was taken by an afternoon in a low sunshine conditions, in the undergrowth: the lighting conditions were not very favorable. The subject is stationary.
The camera was set mode aperture priority. The sensitivity was set to iso-200. In view of the illumination, the temperature was set at 5500 ° K and flash enabled.
To have a sufficient depth of field on the whole subject, I opened to f/20.
With these parameters, the speed is 1 / 100 th of a second.
The camera was mounted on a tripod and it was used a remote trigger to avoid the blur.
The post treatment was to crop the photograph about 75% of original size. The gamma and sharpness were improved by computer.
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- [2010-01-14 6:42]
What a interesting capture this lovely lichen.
Sharp details and colors.