new thread: the cyanide-eating aspect of bamboo lemur diets! can I pls draw your attention to the fact that the bamboos these lemur species feed on contain varying levels of cyanide (some more than others), yet these lemurs have evolved to live largely off of just these plants https://twitter.com/BBCEarth/status/1262105104091697155

this is the video I've summarised in this thread

and here is the relevant research:

http://imc12-2017.m.promaco.currinda.com/schedule/session/114/abstract/685

before I start, I should mention that there are a few different species of bamboo lemurs, and they can eat different species of bamboos, too. so, I'm talking about them generally in this thread, but in reality it is more nuanced

some research has found that that the urine of lemurs that eat bamboo contains high amounts of both cyanide, and thiocyanate, which is the product of the detoxification of cyanide. how much is 'high amounts'?

for reference, in terms of a human, the amount of cyanide found in the urine of these lemurs is similar to what you would expect to see in the urine of a person that were dying or had died of cyanide poisoning...

...and the amount of thiocyanate found in their urine reflects what would look like the borderline level between chronic cyanide poisoning and the tipping point where a human would not be able to support that detoxification anymore.

so what does this mean and how are they eating these cyanide-containing bamboos? the researchers suggest this implies that two separate physiological mechanisms are being used to deal with the cyanide in their diet: increased tolerance to cyanide and and improved detoxification

such high levels of cyanide in urine suggest that these lemurs have increased their tolerance to it in their tissues, possibly by developing mechanisms that prevent cyanide from inhibiting cellular respiration as it might in other mammals.

moving on to thiocyanate, such high levels of it suggest that detoxification pathways have been modified and/or improved. exactly how is unclear, but it may be that these lemurs can either detoxify more cyanide with one enzyme, or have upregulated enzyme production...

...in such a way that they have more of the enzymes required to carry out the detoxification. putative candidate genes involved in these processes of cyanide processing/tolerance are mentioned in the video

who knew so much was going on inside of u???

https://imgur.com/a/M3Sl9 

but wait there are even more mysteries: things get even more interesting here because the cyanide detoxification pathway requires cysteine to produce thiocyanate... but bamboo has very little cysteine. and we don’t know where they get it!!

aaaaaaand, in humans, thiocyanate actually binds to the thyroid in place of where iodine wants to, so humans with chronic cyanide poisoning show symptoms of hypothyroidism (like goitre). this doesn’t happen in lemurs - they show no symptoms or signs

why not? must be due to our different physiologies but it’s intriguing and makes you wonder what other differences we have or don't even know we have

an extra paper that I thoroughly enjoyed https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4988758/