Hot and Scalding

Some organisms manage to harness extreme heat

We all know that dragons and other mythical beasts are frequently given the power of fire-blowing or fire-spitting, but I also know that fire and life don’t mix well and can therefore categorically rule out the existence of fire-producing creatures (with the exception of fire-blowing circus and stage acts). What I am less certain about, however, is what I am supposed to make of stories I heard in rural France, spending 7 months in Moulis, namely that gas production by cows in crowded and badly ventilated stables is said to have been responsible for the occasional explosion. OK, cows produce methane, but who would ignite it? Stranded and decomposing whales on a tropical beach build up gases inside their body due to bacterial activity and can, indeed, explode, but generating fire? No.

Fireflies (not flies, but in reality beetles that are toxic to birds and most other predators), glow in the dark and people who fear to touch the insects, because of their light may be excused, for we do associate light sources with heat. And yet, fireflies and other bioluminescent organisms are said to produce ‘cold light’. Although seemingly correct as you won’t feel any heat when touching a firefly, the light still isn’t 100% cold: there is indeed a very mall component of heat emission, but hardly worth being mentioned in an article on fiery animals. It would be more fitting to mention the seeds of, for example, some plants called pyrophytic, which will not germinate until burnt as is the case with Australian cycads, some eucalypts and banksias in Australia. But then there are, of course, the well known hazards of self-combustion in bacteria or fungus infested piles of hay, grain, oily seeds or pistachio nuts; even cotton has been known to be able to undergo self ignition.

Scorching hot water is another facet of “heat and life” and life without water is certainly impossible. Yet, water -if very hot- isn’t exactly a cosy environment for living organisms and only a few specialized thermophilic bacteria are capable of growing under such ‘heaty’ conditions, which you would find only in certain hot springs and some deep sea hydrothermal vents, where temperatures can reach several hundred degrees C° .There is one group of beetles, however, which as part of their defence reaction, eject a powerful chemical cocktail of hydro-quinones, water, and hydrogenperoxide that can reach temperatures slightly in excess of 100 degrees C: the bombardier beetles. These ground beetles occur on all continents except Australia and Antarctica.

Near their rear ends of the abdomen, these beetles store (or produce at the instant of an attack) fuel in the form of benzo-quinones and hydrogenperoxide, the latter an oxidation agent. These components do not react chemically until they are put under pressure by the beetle’s muscular contraction and then are mixed with minute quantities of enzymes. The enzymes split hydrogenperoxide, release the oxygen, which reacts with the benzoquinones to form highly corrosive breakdown products, which can reach temperatures in excess of boiling water -enough to teach a predator a lesson to give up on this prey. The ejection is accompanied by a clearly audible explosion and a cloudlet of ‘gun smoke’ from the rear end of the beetle. This unusual defence weapon is capable of squirting repeated volleys of a few dozen shots at a dogged attacker – and should that not help to deter a determent foe, the beetle has still one more conventional way of saying “Enough is enough”: it bites!

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2017.
Unauthorized use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to V.B Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com with appropriate and specific direction to the original content.

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