On Glaciers, Moss Become Asexual

Posted by on Apr 21, 2016

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A recent study from the journal Czech Polar Reports presents interesting findings about a rarity on glaciers: moss.

Glacier Mosses(Credit: Flickr)

Glacier Mosses(Credit: Flickr)

When glaciers have a certain amount of moisture and cryoconite—a base layer that consists of small rock particles, soot, and microbes that have accumulated on glaciers— sometimes mosses can grow on them. While it is not common to see moss on glaciers, according to a paper by Olga Belkina, a researcher at the Institute of the Kola Science Centre of the Russian Academy of Sciences, they have been found on a few glaciers in Alaska, Iceland, and Svalbard, Norway.

There are some moss attributes that contribute to the mosses’ tolerance of the brutal living conditions found on glaciers. First, moss do not absorb nutrients from the substrate, the layer to which they are attached, since mosses do not have roots. They absorb water and nutrients directly through their leaves. Mosses only have rhizoids–threadlike tissues which look like roots, but function only to attach to the surface they grow on and can’t absorb water or nutrients from soil or any other substrate.

Second, mosses have have the ability to adapt to a wide range of light levels, which means some types of mosses can survive under massive exposure to sunlight. Some mosses are found in the desert, and some can survive with the low intensity of sunlight found in polar areas.

Glacier Mosses(Credit: Flickr)

Glacier Mosses(Credit: Flickr)

Although glacial areas aren’t the ideal living conditions for mosses, there are still the minimum living requirements for them to grow. There is enough moisture and little competition from other plants, allowing them to survive.

One mystery of the development of mosses found on ice is that how they reproduce in such cold areas. “Failure of sex reproduction of many mosses is widespread in the high polar regions,” the study reports.

The alternative is asexual reproduction. Reproduction strategies for most species fall into two categories, sexual reproduction and asexual reproduction. The offspring of the asexual reproduction process are identical to a single parent, while the offspring from sexual reproduction received genetic information from both parents.

An interesting finding, according to Belkina’s study, is that Schistidium abrupticostatum, a type of moss found on the ice of Bertilbreen, Svalbard, produces gametangia–an organ which produces gametes that can fuse with another cell during fertilization to sexually reproduce. However, the mosses do not evolve into sporophytes, or the non-sexual phase of a plant.

 

Glacier mice(Credit: Wikimedia)

Glacier mice(Credit: Mental_Floss)

Normally plants would alternate between a sexual phase (gametangia) and a non-sexual phase (sporophyte). During the non-sexual phase, plants grow larger and taller to produce spores through meiosis. Then the spores divide into gametes, or sex cells. A gamete from one plant can merge with another gamete, completing a set of chromosomes to start the next round of reproduction.

Generally, mosses do not develop into gametophytes in harsh conditions like glaciers, even though they do in areas that are near the glaciers. Many mosses can be brought to the glaciers by wind and then settle on surface and substratum, yet only a few have the chance to create long-lived populations in such cold conditions.
Each clump of moss on glaciers consists of genetically identical individuals, and the populations grow by the asexual method, which means new mosses can regenerate from a small section of existing moss plants.

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