Why do Arctic predators accumulate vitamin A?

Why do Arctic predators accumulate vitamin A?

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Top predators in the Arctic are known to accumulate vitamin A, often to levels that are toxic for human consumption. A 2012 study by Senoo, Imai, et al. found that the livers of several predator species in the Arctic showed much higher levels of vitamin A than other Arctic species or closely related continental species, with no symptoms of hypervitaminosis A.

Why is it that these species accumulate vitamin A? Does this have something to do with the food sources available in the Arctic as opposed to the mainland? Or are there physiological reasons why Arctic predators would tend to accumulate vitamin A rather than breaking it down or otherwise eliminating it?


  • Senoo, Haruki; Imai, Katsuyuki; Mezaki, Yoshihiro; Miura, Mitsutaka; Morii, Mayako; Fujiwara, Mutsunori; Blomhoff, Rune (2012). "Accumulation of vitamin A in the hepatic stellate cell of arctic top predators". Anatomical Record 295 (10): 1660-8. doi:10.1002/ar.22555. PMID 22907891.

The phytoplankton at the bottom of the food chain have high levels of vitamin A and precursors like beta-carotene. At each step up the chain, vitamin A bioaccumulates. Top predators in the Arctic deal with this by storing the vitamin A in the liver (bears, cetaceans) or blubber (pinnipeds).

This is the same mechanism that causes accumulation of pesticides like DDT in animals.

Carotenoids are part of the photosynthetic system, and also protect the organism from sunlight. Phytoplankton are unicellular, so each cell needs protection. Therefore land plants contain much less carotenoids, since most of the cells are interior and protected from the sun. For example, grains, roots, and wood have very low levels of carotenoids.

This occurs in polar regions due to up-welling nutrient-rich waters supporting high productivity. Temperate and tropical deep ocean regions are typically deserts due to low nutrient levels, particularly iron and fixed nitrogen.

Role of fungal secondary metabolites in plant protection

3.4.2 Terpenes

Terpenes are odorous organic compounds produced by plants mainly having protective actions. Interestingly, fungi also have capabilities that produce terpenes that have a diverse biological role in plants and fungi. Higher fungi are the main source of terpenes. The best-known terpenes are odoriferous plant metabolites such as camphor and turpentine, but fungi also synthesize several valuable terpenes, including aristolochene, carotenoids, gibberellins, indole-diterpenes, and trichothecenes. Chemically, terpenes are made up of several units of isoprene having cyclic-like structures as well as a liner, saturated and unsaturated. It is also observed that terpenes are modified in structure with the addition of extrafunctional groups.

Why you shouldn’t eat a polar bear

Polar bears are cute, especially if they’re still cubs. Knut, a polar bear born in captivity in a zoo in Berlin, was a media sensation. However, they are quite dangerous. Polar bears are big (adults can weigh up to 700 kg), fast (can sprint up to 40 km/h), aggressive, very protective of their young and can kill you with one lazy swipe of their furry paw. Polar explorers are very aware of the dangers of polar bear and bringing a rifle on an expedition is mandatory.

So why should you not eat a polar bear? Well, actually, I’m exaggerating, you can eat polar bear meat, but you better stay away from its liver. To understand why, let’s take a step back.

Obligatory polar bear cubs photo

Vitamins are nutrients that are vital for the correct functioning of our body but which we are not able to synthesise ourselves in sufficient quantities. Without them, we’d die. And since we can’t produce them ourselves, we have to get them from somewhere: from the food we eat. But a substance can be a vitamin to one species and not to another. For example, humans can’t produce their own ascorbic acid (vitamin C) (neither can guinea pigs and apes), but most other animals can. Thus, ascorbic acid is a vitamin for humans, but not for, say, polar bears.

Vitamins are very useful, vital even, in small doses, but can be quite deadly if we absorb too much of them.

But why am I talking about vitamins? Animals that live in the cold tend to have very high amounts of vitamin A in their liver as it’s very helpful in the freezing environment. The liver of polar bears, seals, walruses and huskies all have tons of vitamin A stored in them.

More polar bear cubs for maximum internet points

Hypervitaminosis A

When we absorb too much vitamin A bad things happen. Your skin loses colour and starts to peel off. Your hair starts to fall out. You lose muscle coordination, you have nausea, vomiting and dizziness. And then you might die. The condition is called hypervitaminosis A. What happens is that your liver, which stores vitamin A, has a limited amount of space. When the vitamin exceeds the storage capacity it enters the bloodstream. It can then cause your cells to swell up with fluid and since it’s liposoluble, it can affect your brain. Not. Nice.

The first report of people feeling ill from polar bear liver is from 1597, though the Inuit have known about the dangers for much longer. They throw the liver to sea or bury it so that their dogs don’t eat it and fall ill or die. Two members of the Far Eastern Party, an antarctic expedition, were probably poisoned by vitamin A after eating the liver of their huskies. One of them died.

And that’s why you shouldn’t eat polar bear liver.

Unsurprisingly, the majority of cases of hypervitaminosis A are not due to people eating polar bear liver (it’s not like any of us have a chance to do it) but due to the overuse of vitamin pills. Remember, there’s a reason why there are recommended dosages on the box.

Logistic Population Growth levels off at a carrying capacity

To consider how resource limitation affects population growth, we need to incorporate the concept of carrying capacity, the maximum population size that the environment can sustain. Any individuals born into this population would increase the population size unless the number of deaths balanced or outnumbered births. If the population size remains the same from one generation to the next, then individuals must also be dying at a similar rate. With exponential population growth, the population growth rate was constant. With the addition of a carrying capacity imposed by the environment, the logistic population growth rate slows as the population size increases, and growth is zero when the population reaches carrying capacity.

When resources are limited, populations exhibit logistic growth. In logistic growth, population expansion decreases as resources become scarce, and it levels off when the carrying capacity of the environment is reached, resulting in an S-shaped curve. Source: OpenStax Biology

Strategies of insect cold hardiness

By way of a summary, it is often stated that there are two main strategies of insect cold hardiness — freeze tolerance and freeze avoidance by supercooling. The key difference between these strategies is the synthesis of ice nucleating agents (proteins) in freeze-tolerant species and the removal of all potential nucleators, such as gut content, from freeze-avoiding species. Ice nucleating agents are usually synthesised in autumn and initiate freezing at temperatures in the region of −4°C to −10°C, in so-called ‘safe extracellular areas’ such as the haemocoel as a result of ice freezing out of solution, water then moves progressively from cells to these areas to re-establish the osmotic equilibrium (Fig. 1). The net effect is that when the insect experiences the lowest temperatures of mid-winter, the cell fluids have become sufficiently ‘cryo-concentrated’ to avoid intracellular freezing, which is regarded as deleterious or lethal in most insects (see also Lee et al., 1993). Both freeze-tolerant and freeze-avoiding species may also contain polyols and sugars (e.g. glycerol and trehalose, respectively) and antifreeze (thermal hysteresis) proteins, although the function of these agents differs between the two strategies (Fig. 2). As the number of studies on freeze-tolerant species has increased, the temperatures at which the nucleators initiate freezing at the ‘supercooling point’ (SCP) have been found to be generally consistent between species (mean usually above −10°C). However, the lethal temperature has been shown to be much more variable, ranging from −10°C in the sub-Antarctic beetle Hydromedion sparsutum (Müller) (Bale et al., 2000) to −25°C in the temperate hoverfly Syrphus ribesii L. (Hart and Bale, 1997) and −40°C or lower in the North American gallfly Eurosta solidaginis Fitch (Bale et al., 1989a Bale et al., 1989b). The survival of species such as H. sparsutum with a ‘high’ lethal temperature in a sub-Antarctic climate would seem to depend on the thermal protection provided by the decaying leaves of its host plant Parodiochloa flabellate (Lam.) and the cover of winter snow. As well-studied species, E. solidaginis and the autumnal moth Epirrita autumnata Bkh. exemplify the features of the freeze-tolerant and freeze-avoiding strategies — in the latter case, the overwintering eggs of E. autumnata survive through the harsh Scandinavian winters above snow level as long as the air temperature does not fall below the SCP of −36°C (Tenow and Nilssen, 1990).

Schematic representation of the function of extracellular ice nucleating agents in a freeze-tolerant insect [• indicate sites of nucleation in extracellular areas and increasing ice masses at progressively lower sub-zero temperatures from summer (1) to mid-winter (4)] (see Bale, 2002).

Schematic representation of the function of extracellular ice nucleating agents in a freeze-tolerant insect [• indicate sites of nucleation in extracellular areas and increasing ice masses at progressively lower sub-zero temperatures from summer (1) to mid-winter (4)] (see Bale, 2002).

One of the problems of trying to place the cold hardiness of insects in general within the alternative strategies of freeze tolerance and avoidance is that these strategies were derived from studies on cold-hardy insects living in cold and very cold climates, whereas the majority of species live in much less severe climates, and biodiversity is greatest in the tropics. A range of studies have shown that whilst most insects have considerable potential to ‘supercool’ (in the absence of gut content), a low SCP is not necessarily indicative of cold hardiness. For example, there are many species with winter SCPs of −25°C but when held at higher sub-zero temperatures, mortality increases after exposures of 1-3 months [e.g. the beech weevil Rhynchaenus fagi L. (Bale, 1991)] or only a few minutes [e.g. the aphid Myzus persicae (Sulz.) (Bale et al., 1988 Clough et al., 1990)]. With species of tropical and Mediterranean origin, high mortality can occur whenever the insects experience temperatures below the developmental threshold, i.e. between 10°C and 0°C (Hatherly et al., 2005) hence, overwintering of such species in cool temperate climates is dependent on a high level of thermal protection. With respect to the effects of cold exposure, Bale described species such as R. fagi, M. persicae and tropical insects as ‘chill tolerant’, ‘chill susceptible’ and ‘opportunistic survivors’, respectively. In reality, the terminology is not important — the key point is that most insects are neither freeze tolerant nor freeze avoiding (because they are killed by the effects of cold, not freezing), and this diversity of thermal tolerance needs to be recognised in any generalised consideration of the impacts of climate warming on insect winter survival (Bale, 1993 Bale, 1996).


The polar regions (the Arctic and Antarctic) are characterized by continuous light in the summer and almost total darkness, blizzards, scarcity of food and temperatures occasionally as low as −60°C in the winter. The Arctic is defined as the area north of the 10°C isotherm for July, whereas the Antarctic is the area south of the Antarctic Convergence (see Glossary) Arctic and Antarctic animals are those having their winter residency and main area of distribution within those boundaries (Box 1) (Irving, 1972 Blix, 2005). Probably because of the challenges imposed by this environment, the number of species that can cope with life in the polar regions is low, but most of those that prevail occur in large numbers. The effects of global warming are particularly felt in the polar regions, and an understanding of the needs of the animals therein and their tolerances to environmental change is greater than ever. This Review will focus primarily on the adaptations (see Glossary) of young and adults to low temperatures, and the effects of scarcity of food and lack of light during winter, as well as continuous light during summer, on animals that are permanent residents in polar regions.

The terrestrial Arctic animals discussed in this Review are the polar bear (Ursus maritimus), polar wolf (Canis lupus), Arctic fox (Vulpes lagopus), ermine (Mustela ermina), muskox (Ovibos moschatus), reindeer/caribou (Rangifer tarandus), Arctic hare (Lepus arcticus) and lemming (Dicrostonyx sp./Lemmus sp.). The marine Arctic animals that are discussed are the bowhead whale (Balaena mysticetus), narwhal (Monodon monoceros), white whale (Delphinapterus leucas), bearded seal (Erignatus barbatus), ringed seal (Pusa hispida), hooded seal (Cystophora cristata), harp seal (Pagophilus groenlandica), ribbon seal (Histriophoca fasciata) and walrus (Odobenus rosmarus).

In the Antarctic there are no land mammals, but there are marine mammals, such as the crabeater seal (Lobodon carcinophagus), Ross seal (Ommatophoca rossi), Weddell seal (Leptonychotes weddellii) and leopard seal (Hydrurga leptonyx), which are closely associated with the pack ice.

The true Arctic birds are the snowy owl (Nyctea scandiaca), raven (Corvus corax), rock ptarmigan (Lagopus mutus) and Arctic redpoll (Carduelis hornemanni), as well as some little-known seabirds such as the ivory gull (Pagophila eburnea) and Ross gull (Rhodo rosea). In Antarctica, there are no resident terrestrial birds, but resident marine birds, such as Emperor (Aptenodytes forsteri) and Adélie (Pygoscelis adeliaestethia) penguins, Antarctic petrels (Thalassoica antarctica) and snow petrels (Pagodroma nivea), are abundant.

In addition, there are multitudes of migratory mammals and birds that visit the polar regions during summer. The Arctic ground squirrel (Citellus parryi) and the Djungarian (or Siberian) hamster (Phodopus sungorus), for example, are hibernators that are not normally considered as truly Arctic mammals (and hibernation is not a common Arctic strategy). However, the range of these animals extends into the Arctic, where they have been much studied (Heldmaier et al., 2004). They will therefore be considered, in brief, in this Review, and some studies of other sub-polar species with obvious relevance for the true polar species are included.

New residents from the South

A warmer and longer growing season may be an advantage for some species, but specialized Arctic wildlife could be negatively affected. For example, there has been a significant increase in vegetation productivity across the entire Arctic, in part because of increased growth and encroachment of shrubs and trees, but there’s also been reduced cover of more typical Arctic species such as lichen and moss. Southern species moving into the Arctic reduce space for northern species and complicate their interactions. The START reports that range extensions of more southern species such as red fox, moose, American beaver and snowshoe hare, are introducing new herbivore competitors and potential predators into Arctic ecosystems.
“Arctic biodiversity is unique because it’s condensed in a small area,” says Tom Christensen. “We can see that because of climate change, and as southern species move North, Arctic species will have to move even further North. Eventually, there won’t be any space for them left.”

So far, the impacts of southern invasive species on Arctic species are unclear. But it may not be long before it becomes a more prominent issue in the Arctic. “Invasive species establishing themselves in the Arctic may be starting off very slowly, but as the invasive species accumulate, they can grow exponentially as time goes on,” says Starri Heiðmarsson, Co-Chair of CBMP Terrestrial.

“Luckily, we’ve been able to monitor this issue of invasive species, and it’s early enough that there are things we can do to prevent problems. For example, there’s an eradication program for invasive plants in Svalbard, when just five or ten years ago there had been no reason for such a program,” adds Mora Aronsson.

Boreal Forests

The boreal forest, also known as taiga or coniferous forest, is found south of the Arctic Circle and across most of Canada, Alaska, Russia, and northern Europe (Figure 8). This biome has cold, dry winters and short, cool, wet summers. The annual precipitation is from 40 cm to 100 cm (15.7–39 in) and usually takes the form of snow. Little evaporation occurs because of the cold temperatures.

Figure 8. The boreal forest (taiga) has low lying plants and conifer trees. (credit: L.B. Brubaker)

The long and cold winters in the boreal forest have led to the predominance of cold-tolerant cone-bearing plants. These are evergreen coniferous trees like pines, spruce, and fir, which retain their needle-shaped leaves year-round. Evergreen trees can photosynthesize earlier in the spring than deciduous trees because less energy from the sun is required to warm a needle-like leaf than a broad leaf. This benefits evergreen trees, which grow faster than deciduous trees in the boreal forest. In addition, soils in boreal forest regions tend to be acidic with little available nitrogen. Leaves are a nitrogen-rich structure and deciduous trees must produce a new set of these nitrogen-rich structures each year. Therefore, coniferous trees that retain nitrogen-rich needles may have a competitive advantage over the broad-leafed deciduous trees.

The net primary productivity of boreal forests is lower than that of temperate forests and tropical wet forests. The aboveground biomass of boreal forests is high because these slow-growing tree species are long lived and accumulate standing biomass over time. Plant species diversity is less than that seen in temperate forests and tropical wet forests. Boreal forests lack the pronounced elements of the layered forest structure seen in tropical wet forests. The structure of a boreal forest is often only a tree layer and a ground layer (Figure 8). When conifer needles are dropped, they decompose more slowly than broad leaves therefore, fewer nutrients are returned to the soil to fuel plant growth.

Species are at risk of extinction

A global mean temperature rise of 2 to 3 °C will greatly increase the percentage of species at risk and amplify the dangerous impacts on biodiversity and ecosystems. If an ecosystem is already degraded from other causes not related to climate, such as pollution, a species is less resilient or likely to adapt. The animals shown here illustrate the wondrous diversity of life on Earth, and also highlight the many ways climate change puts all forms of life on the planet, including humans, at risk.


Linda Crampton (author) from British Columbia, Canada on August 09, 2019:

I&aposm sure many people have burnt logs with lichen on them and come to no harm. I can&apost guarantee that the process is safe for every type of lichen, however.

To be reasonably sure of safety, especially since the logs will

be in close proximity to food, you would need to scrape the lichen off. Another thing you could do is to show the lichen or a photo of the lichen to a scientist who studies the organisms

and ask for their opinion.

Scott on August 09, 2019:

After reading your comments on lichen, I see there are still a lot of unknowns. but I&aposll ask anyway. I use wood covered in lichen from my apple tree in my BBQ to flavor the meat. Should I burn it or scrap it off before burning to be safe?

Linda Crampton (author) from British Columbia, Canada on July 05, 2019:

No, they don&apost. They are sometimes seen in particular areas on a tree trunk (which may face north, south, or any other direction). The environmental conditions in a particular microhabitat on the trunk determine whether or not a specific type of lichen can grow there.

John Yeager on July 04, 2019:

Do lichens tend to grow on a particular side of trees like either the north side or south side?

Linda Crampton (author) from British Columbia, Canada on October 17, 2018:

Hi, Monika. I have no experience in using lichens in the way that you describe. I do have lichens on dead branches in my garden. They dry out when the weather is warm and then rehydrate when the atmosphere is moist. I think they might dry out too much and become brittle if they were stored indoors. I&aposve read that some artists treat lichens with glycerin before using them in a project. This is something that you might want to investigate.

Monika on October 15, 2018:

I was thinking of combining lichens (from a dead branch) with fabric and yarn to create collages and frame them in shadow boxes. Is this something that&aposs OK to do? Or will the lichens decompose inside the frame? thanks!

Linda Crampton (author) from British Columbia, Canada on July 07, 2018:

Hi. Lichens do contain iodine, but I don&apost know the typical concentration that&aposs present. I have no idea whether a particular extract or supplement made from lichen has iodine in it or whether the iodine is at a significant level if it is present. You would have to send a sample to a reputable laboratory and get it analyzed for its chemical content. The test should include an analysis for both iodine and vitamin D.

rivaorourke on July 07, 2018:

I really need to know if lichen contains iodine. We have a source of vitamin D3 that derives from lichen, and need to know. Thanks!

Linda Crampton (author) from British Columbia, Canada on May 13, 2018:

Hi, Soheil. Wolf lichen is attractive, so I can understand why you would want to display it. I would suggest that you put it out of reach if children or pets enter the home as guests, though. Other than that, I would leave it on display (as long as it survives). Some people extract dye from the lichen, so it doesn&apost seem to be dangerous to touch. It&aposs always a good idea to wash the hands after handling items from nature, though, especially before eating.

Soheil on May 13, 2018:

Thanks for the article. It is very helpful. I have a question for you though, recently, while hiking, I found a beautiful Wolf Lichen growth on a dead branch. It was so beautiful that I took the branch home and put it as decoration in my living room. Knowing that it is poisonous, I got a little stress now. Do you think it is better to remove it? Is it harmful touching it or having it at home? We don&apost have pets or children, so no one would chew it.

Linda Crampton (author) from British Columbia, Canada on March 26, 2018:

I&aposm glad the article was helpful for you.

Linda C on March 26, 2018:

Just what I needed for my trail talk about usable plants! Thanks!

Linda Crampton (author) from British Columbia, Canada on March 18, 2018:

Hi, Vivian. Lichens grow on many tree trunks where I live, too. They&aposre interesting to see.

vivian gerard on March 18, 2018:

just had some growing on some trees was just wondering about yes its one on north side plus west side on a certain tree its a lions head maple planted in a pot

Linda Crampton (author) from British Columbia, Canada on February 20, 2018:

Narendra on February 20, 2018:

Thank u very much for giving lot of knowladge about lichen

Linda Crampton (author) from British Columbia, Canada on September 27, 2017:

Hi, Ernie. A survey of your local lichens sounds interesting. A book about the lichens that grow in your part of the world could be useful for you. One with colour photos and descriptions of the different types would be especially helpful. There may be identification guides for the lichens in your area on the Internet as well. This is probably the best place to check first of all.

Ernie A. Bonzo on September 27, 2017:

Lichens are fascinating. Such a big help in the environment. I am mentoring 2 groups of high school students who are also interested with Lichens. we just want to survey our area here and find out the presence of lichens and their quantity. Can you help us Identify and Classify Lichens?

Linda Crampton (author) from British Columbia, Canada on June 17, 2017:

Thank you very much, Vikas.

Linda Crampton (author) from British Columbia, Canada on June 15, 2017:

RAMAKRISHNA on June 15, 2017:

Thanks you lot giving information about lichen

Linda Crampton (author) from British Columbia, Canada on April 13, 2017:

Louise, I&aposm sorry that you&aposre having so many problems and that you&aposve had them for such a long time, but my article has nothing to do with lichen planus. Lichens are organisms that live in the environment, not on or in the human body. I can understand why you&aposre confused because the names are so similar, but lichen planus is thought to be an autoimmune disease, not an infection. I&aposm not a doctor and can&apost offer you any advice about your condition. From what I&aposve read, though, dermatologists often deal with the disorder. Perhaps your doctor can recommend one, or maybe a different doctor can help you. I hope you find someone that can improve your condition.

Louise Svadeba on April 13, 2017:

I have been diagnosed with lichens paleous. It lives directly under my skin and some go deeep into my body. They look like a spreading out of little "road maps" and NOTHING I HAVE TRIED WILL KILL THESE, NOR THE ONES THAT GO DEEEP. After the biopsy,. That I thought went extremely deep, the lichen began and is still coming to the surface, it now itches. None of them have ever itched, much, unless I tried to remove them, with the MANY VARIOUS CREAMS THAT MY Dr. Prescribed, the last being​, forgive my spelling, Perythrian, topical cream. It seems to have done the MOST to rid myself of them.

There seems to be a &apospattern&apos to some of them, such as VERY near perfect circle of dots about this size : O, maybe bigger, some smaller, but they all have a bit bigger one in the center. When IT (the center one) itches and dies, the other ones sink into my skin and it seems as my body does away with it. They DO LEAVE A very slight indentation ,however that reminds me that it was there. So very very odd!!

Oh, yes, and BLEED!! WOW ! they bleed ALOT , but for only a minute or so and that&aposs it. That was when I was trying diligently to remove them, they are quite UGLY, you know!! But, anyway HOW ON EARTH DID THEY GET INTO ME AND HOW DO I KILL THEM. ALL. ALSO I HAVE HAD THEM FOR (Here is the kicker. 40 years. ) No DR. Until now has admitted to even seeing them under my skin. CAN YOU HELP ME? OR KNOW WHO CAN. FYI . They are on my extremities, and a little on my face. Even under my toes and my breasts and decoulage(upper chest) in case I spelled it wrong. . Please RSVP and ASAP. THANKS AGAIN, LOUISE SVADEBA

Linda Crampton (author) from British Columbia, Canada on March 28, 2017:

I think you&aposll find lichens interesting to study. I do!

Kohl on March 28, 2017:

Hay thank you so much for the post :D I&aposve really wanted to get into studying lichen

Linda Crampton (author) from British Columbia, Canada on March 16, 2017:

Thank you. I&aposm glad that the article was helpful.

aqsa arshad on March 16, 2017:

amazing this helped me alot in making my assignment

Linda Crampton (author) from British Columbia, Canada on March 07, 2017:

Hi, Venetia. Thank you very much for the comment. I&aposm afraid that I don&apost know of any source of prepared lichen powders or dyes. People who want to use the dye make it themselves, as far as I know. Good luck with your use of lichens in art.

venetianev on March 07, 2017:

This is fascinating and very inspiring! I am an artist from England, working with mainly organic materials and have recently been using algae powders in paintings. Would love to access some lichen powder or dyes and wonder if you could recommend a good source. Or it would be wonderful some day to make my own powder .

Thank you so much for sharing your riveting information about lichen and particularly for putting it in a way that is so easy to understand,

Linda Crampton (author) from British Columbia, Canada on February 01, 2017:

As far as I know, the answer to your question is no. You should contact a lichenologist for confirmation, however. That being said, I always wash my hands after time spent handling soil, decaying bark or similar substrates because they may contain harmful microbes. In addition, I wear a mask if I handle anything that&aposs releasing particulate matter into the air because the particles may be harmful to the lungs.

Diane on February 01, 2017:

Is there danger in handling certain lichen, either transferring onto fingers or breathing in harmful components of disturbed lichen?

Linda Crampton (author) from British Columbia, Canada on September 30, 2016:

Hi, edgardo. Lichens seem to be generally harmless or helpful to humans, but there are some potentially harmful aspects to them. In addition to the problems I&aposve mentioned above, researchers have found that some lichens produce chemicals called microcystins that can damage the liver.

edgardo on September 29, 2016:

hi ma&aposam. can i ask question? what is other harmful effects of lichen?

Linda Crampton (author) from British Columbia, Canada on September 26, 2016:

Earl on September 26, 2016:

Wow! this is the best and the most helpful article about lichen.

Linda Crampton (author) from British Columbia, Canada on April 30, 2016:

Thank you, Heidi. I appreciate your comment and congratulations very much. I hope you have a great weekend, too!

Heidi Thorne from Chicago Area on April 30, 2016:

I think the most interesting is the natural sunscreen aspect. Another informative hub deserving of the Hub of the Day it just received. Congrats and have a great weekend!

Linda Crampton (author) from British Columbia, Canada on April 30, 2016:

Thank you very much for the congrats, Kristen! I&aposd miss seeing lichens if they disappeared from my neighbourhood. I enjoy observing and studying them.

Kristen Howe from Northeast Ohio on April 30, 2016:

Linda, congrats on another HOTD! This is so fascinating and amusing to know about the facts on lichens. I remember when I lived in NJ, there was lichen on one of the trees. I remember it was a greyish color like in the photo. I haven&apost seen any here since I lived in Ohio for 16 years now. Kudos!

Linda Crampton (author) from British Columbia, Canada on April 30, 2016:

RTalloni on April 30, 2016:

Interesting, yes--lesson in not switching thoughts in the middle of a sentence. :) Always enjoy your work.

Linda Crampton (author) from British Columbia, Canada on April 30, 2016:

Thank you for the interesting comment and the congrats, RTalloni. I think it&aposs important that we don&apost dismiss lichens, too. They are an important part of nature.

Linda Crampton (author) from British Columbia, Canada on April 30, 2016:

Thanks for the comment, Oztinato! I appreciate your visit.

RTalloni on April 30, 2016:

How amazing that lowly lichens have so many uses to make us like &aposem! ) Seriously, though, as technology allows us to unfold the intricacies of nature&aposs details we continue to learn that we have much to learn about what creation has to say to us. This hub has reminded me that the earth was designed to rejuvenate itself (but that does not mean we are not to be good stewards!). Coming across these in the wild would make the average person dismiss them but that is a lesson that falls in the importance of not doing so. Thanks for a neat read and congrats on your Hub of the Day award.

Oztinato on April 30, 2016:

I&aposm really liken your hub on lichen. Very interesting and informative.

Linda Crampton (author) from British Columbia, Canada on February 17, 2016:

Hi, Student101. There are references in the blue boxes in this article, although I may change the colour and position of the boxes when I do my next edit of the article. The general information about lichens comes from my education and knowledge as a biology teacher. Good luck with your research.

Student101 on February 17, 2016:

can you share your reference for this one. I just need for my research pleasee @AliciaC

Linda Crampton (author) from British Columbia, Canada on October 18, 2015:

Thank you very much, ammara. I&aposm glad the article helped you.

Linda Crampton (author) from British Columbia, Canada on October 18, 2015:

That&aposs interesting, khan. I haven&apost heard of that use before.

ammara salman on October 14, 2015:

Awsome article. Helped me alot

khan on September 19, 2015:

i saw in a video lichen is used for dying hair,

Linda Crampton (author) from British Columbia, Canada on December 28, 2014:

Thank you for the comment, Elsie. I&aposm sorry about the problem that you&aposre having with lichens. I&aposll read your hub very soon. Thanks for such a lovely new year&aposs wish. I hope 2015 is a wonderful year for you, too!

Elsie Hagley from New Zealand on December 28, 2014:

Very interesting. I have just written an article about Usnea Lichen which is killing the trees in my garden.

So I&aposm not happy with it camping in my garden, it is a eyesore and makes my garden very untidy with dying tree.

Happy New Year to you, hope 2015 is a perfect year for you.

Linda Crampton (author) from British Columbia, Canada on January 12, 2014:

Thanks for the comment, WriterJanis. I think that many lichens look pretty. They are interesting organisms, too.

Janis from California on January 12, 2014:

You have so much great info here. Some of your photos make lichens look pretty.

Linda Crampton (author) from British Columbia, Canada on January 09, 2014:

Thank you very much for the kind comment and the votes, DDE!

Devika Primić from Dubrovnik, Croatia on January 09, 2014:

Brilliantly put together and now I know so much more about this topic. I have seen Lichens and just did not bother much about it until I read this hub. Voted up, useful, and a very helpful hub indeed.

Linda Crampton (author) from British Columbia, Canada on January 07, 2014:

Hi, Deb. Yes, lichens are amazing! They are very common in British Columbia, too. I enjoy observing them.

Deb Hirt from Stillwater, OK on January 07, 2014:

Lichens are utterly amazing. I never realized that they had so many god and very important uses. When I walked in the woods back home in Maine, they were everywhere.

Linda Crampton (author) from British Columbia, Canada on January 04, 2014:

Thank you very much, Sue. I think that lichens are fascinating, too! I appreciate your visit.

Susan Bailey from South Yorkshire, UK on January 04, 2014:

Fascinating subject. Who would have thought lichens were so interesting. Great hub!

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Thank you, Dianna. It is very interesting that lichens can be used in so many ways. They are useful organisms.

Dianna Mendez on January 02, 2014:

Fascinating article on lichens! It is amazing how they are used in products.

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Hi, ologsinquito. I agree - lichens probably have medicinal benefits that we are unaware of. It&aposs important that we don&apost destroy them! Thank you very much for the comment, the vote and the pin.

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Thank you very much for the comment and for sharing your experience, Audrey!

ologsinquito from USA on January 02, 2014:

Great article. They probably do have some good medicinal uses, probably ones we don&apost even know about. Voted up and pinned.

Audrey Howitt from California on January 02, 2014:

Lichens make a wonderful dye for silks and wools--Loved your article!

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Thank you very much, Cynthia. I always appreciate your visits and kind comments!

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Thank you for such a lovely comment, Bill! I appreciate it very much. Thanks for the vote and the share, too. Happy New Year!

CMHypno from Other Side of the Sun on January 02, 2014:

I always learn so much from your hubs Alicia. Thanks for all the great information on lichens and the really interesting photos

Bill De Giulio from Massachusetts on January 02, 2014:

Hi Linda. What an interesting and informative read. Great job. Exceptionally well written. My education continues. Voted up and shared. Happy New Year

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Thank you for the visit, JSMatthew. I appreciate your comment and vote, as well as the share!

JS Matthew from Massachusetts, USA on January 02, 2014:

This is very interesting. I never thought something so simple could be so complicated! Well done. Up and shared.

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Yes, the scent does sound exotic! I&aposd like to try it, too. Thanks for the comment, EGamboa.

Linda Crampton (author) from British Columbia, Canada on January 02, 2014:

Thanks for the visit and the comment, Eddy. I hope you have a great day, too!

Eileen Gamboa from West Palm Beach on January 02, 2014:

I just want to find a perfume with Oakmoss. Sounds exotic. Great article!

Eiddwen from Wales on January 02, 2014:

Another very interesting and useful hub by you again Alicia.

Linda Crampton (author) from British Columbia, Canada on January 01, 2014:

Thank you, Jodah! I appreciate the comment and the vote very much. It is interesting that lichens have so many present and potential uses.

John Hansen from Queensland Australia on January 01, 2014:

Alicia, this is a very comprehensive guide to lichens. I knew very little about them before, except they were related to fungi, so you taught me a lot. Never realised they had so many uses. Voted up.

Linda Crampton (author) from British Columbia, Canada on January 01, 2014:

Thank you so much for the comment, the link and the votes, Peggy! Happy New Year to you, too, and best wishes for an excellent 2014!

Peggy Woods from Houston, Texas on January 01, 2014:

Fantastic article Alicia! I added a link from this hub to mine titled Pictures of Mushrooms and Fungus - Wild Ones! UUI votes. Happy New Year!

Linda Crampton (author) from British Columbia, Canada on January 01, 2014:

Thank for very much, Faith. I appreciate your votes and share, as always. Happy New Year!

Linda Crampton (author) from British Columbia, Canada on January 01, 2014:

Thank you very much for the kind comment, MJ! I hope that 2014 is a great year for you.

Faith Reaper from southern USA on January 01, 2014:

Fascinating hub as always! I am glad you included how to pronounce these organisms. I have seen these on tree banks, but had no clue as to what they were, but now I do and will keep my eyes open to spot them. That photo of yours is awesome too.

Marcy J. Miller from Arizona on January 01, 2014:

Wow. I savored every word of this fascinating article. I had no idea lichens were used in making litmus paper . Nor that they had so many other practical uses and potentials. It&aposs amazing how very complex such seemingly simple organisms can be. Love this sort of information!

Linda Crampton (author) from British Columbia, Canada on January 01, 2014:

Thank you very much for the lovely comment, Bill. I always appreciate your visits and support!

Bill Holland from Olympia, WA on January 01, 2014:

Always informative. always useful. always valuable. Thank you for the continuing education my friend.

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