The Living Dead

Heart attacks and the “Playing Possum” phenomenon – Halloween article

Heart attacks take a considerable toll on the human population and various programmes to reduce the risks of heart failure through special diets and behaviour (saltfree fish and chips, no smoking, daily jogging, yoga exercises etc.) have been advocated. However, we are of course not the only mammals to suffer from coronary diseases and other problems with our vital pump: pigs on the way to the slaughterhouse, animals under stress, enraged or in fear can collapse and die from heart failure. Others -and here we come to the possum part- fake death. They do it so cunningly, instinctively, and convincingly that a predator in search of a fresh meal may not accept the seemingly uninteresting carcass as food. Triggers for predators to be interested in prey often involve prey to move, to struggle and to attempt to get away. If such clues are missing a predator may not react.

“Playing possum” is a widespread survival strategy found in a variety of mammals and in a form of “thanatosis” also amongst innumerous species of insects, spiders and other invertebrates. In the state of faked deaths amongst mammals, the body temperature may fall, blood circulation ceases, the heart beat stops, limbs are flaccid, and sensory reflexes are non-existent. Sometimes regurgitated food around the mouth may be present.

We humans exhibit many animal behaviours during times of fear and stress. We pale, sweat, tremble with fear, get goose-pimples of fright, may be paralysed by impending danger and, according to Viennese Professor A.D. Jonas, we can arrest our heart beat like possums or other animals in times of extraordinary stress. The only part we have trouble with is making our heart go again, waking up from faking death, releasing us from “playing possum”. Prof Jonas suggested that heart attacks may often be no more than an escape behaviour, which we have inherited from our primitive ancestors, but what to our chagrain in the course of evolution we seem to have lost is the ability to start our vital functions again once the danger has passed.

There is no such problem with invertebrates, which may respond to an attack by reducing their body size through coiling up and withdrawing their limbs and by becoming immobile and impervious to stimulation. When the danger has passed they wake up from their state of thanatosis and usually scuttle away quickly. Pill bugs and millipedes are good examples. They roll up into a ball or a spiral and remain motionless until they feel safe; beetles when disturbed and unable to fly away may pretend to be dead and an insect, perhaps a grasshopper, caught in a spider’s web will seek initial refuge by remaining stock still for a while as if to gather their strengths and will then suddenly making a violent attempt to free themselves. On the other hand, orb web spiders when disturbed in their webs may just drop down, entering a state of thanatosis amongst the vegetation or leaf litter, before ascending the safety line to their web again, a silk thread they had left while dropping down.

There is no doubt that deception has a long evolutionary history, that feigning death and “playing possum” can save lives – as long, of course, as Prof. Jonas has pointed out, the bluff does not become permanent.

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Afraid of zombies ? click for another story : “Parasitic manipulations”

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2016.
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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Something’s in the air

And it doesn’t smell too good

A good friend of mine is a doctor on a cruise ship and he could tell you a thing or two about the behaviour and the diseases of seamen and tourists, but that’s not what I want to write about. This good doctor friend of mine claimed he could identify illnesses simply by what he smells when entering a patient’s room. Sniffing at a sick person’s clothes, bed sheets or ears would give him further valuable clues, he said. And in this way he’d be able to diagnose, with his nose, stomach, liver and bladder anomalies as well as various other ailments ranging from the common cold to diabetes and even some forms of cancer.

Under normal circumstances a healthy adult contains about 150 ml (about a tea cup full) of gas at any one time in the gut. That gas is a mixture of CO2, methane, and minor foul-smelling components. This gas mixture is actually a potent greenhouse gas and it takes little imagination to think of the effects that the world’s farmed cattle population, estimated to be around 1,500,000,000 heads, has with regard to gas emissions and global climate change!

But back to us humans. Over a single day a person releases approximately 600-1,200 ml of the gas mixture mentioned above, most of it in a little-polite way through the rear end of his or her body. Some gas, however, makes its way up via the stomach to the mouth and another component is carried by the blood from the gut to the lungs, where it is breathed out in the normal way. Sweat can also be involved in releasing odours. Although some gas stems from swallowing, the majority of it is actually produced by gut microorganisms and represents breakdown products of mainly non-digestible carbohydrates in the food that a person has ingested. Everybody, and especially children all over the world, know that legumes and cabbage are very potent food in this regard (but let me tell you cherries can work quite well, too).

Anyway, if the composition of these gut organisms is disturbed through diseases or poisons, the composition and chemical natures of the gases produced inside our intestine also changes. Someone with a trained nose, like my ship’s doctor friend, can then indeed diagnose certain disorders from the odour a patient emits. That this ability can have embarrassing side effects is clear: when my friend met our captain’s wife for the first time and had exchanged a few words with her, he suddenly uttered, audible to everyone around: “Your exterior is delightful, madam, but inside there’s something rotten and you had better have your liver checked.”

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Do you smell the Autumn? Click here for reading “Autumn colors”

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2016.
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.

Gimme Shelter

But antifreeze may also work quite well

As a member of several Antarctic expeditions of my university and the leader of Jamaica’s first (and only) Antarctic research trip in 1993, I was naturally concerned with the clothes we had to take along to keep us warm there. But the question that also arose in a situation like this was, how do organisms, generally, cope with the intense cold that occurs at high latitude or high altitude regions?

If you are a warm-blooded, endothermic, animal, you have less of a problem than a cold-blooded, ectothermic creature, for you can generate your own heat – provided of course you have the “fuel” for your body furnaces to burn and turn into inner warmth. Poor Robert Falcon Scott and his men, after having reached the South Pole on January 17, 1912 one month after being beaten by the Norwegian Roald Amundsen, simply did not have sufficient calorific intake and died of cold, starvation and exhaustion on their return from the Pole to Base Camp. Amundsen, incidentally, disappeared 1928 in the Arctic with a search plane trying to rescue members of Italian Umberto Nobile’s ill-fated airship expedition to reach the North Pole.

As a warm-blooded creature, sure, you lose body heat to the cold environment, but if your body volume is not too small and you possess dense feathers, a thick coat of fur or an insulating layer of blubber/fat, you can feel warm nonetheless. After all, it’s easier to keep warm in the cold than it is to keep cool in the heat. Without some heat-conserving adaptations, however, there are only three other possibilities to survive in the cold. The first, used by both warm and cold-blooded animals, is to move away from the cold and to seek out sheltered places, to rest and conserve energy. Hibernation, sleeping the winter away, would be the best option, but it is not available to everyone and, for instance, sheltering in loose snow against an icy wind can only be maintained as long as the need to feed and search for food isn’t greater than the need for sheltering.

The two remaining methods apply to cold-blooded animals only: some insects like, to name but two, are the larvae of an Alaskan chironomid mosquito and the adults of a New Zealand mountain weta (a sort of huge cricket). They together with tiny bear-animalcules, some nematode worms and a few other microscopic organisms, for reasons often not yet fully understood in all detail, can tolerate total freezing of the tissue and will revive upon thawing. Fish, frogs, snakes and lizards, with very few exceptions, cannot come back to life if frozen stiff. The exceptions are the Siberian lizard Zootaca vivipara, which may survive in the frozen state a temperature down to -10°C, and the Siberian salamander Salamandrella keyserlingi that is known to survive even temperatures to at least -30°C.

Certain Antarctic fish species, whose eyes and vision I had studied while in Antarctica, are able to depress their tissue freezing point by a couple of degrees with the help of antifreeze molecules in their blood. The antifreeze substances, as Art DeVries has shown, consist of molecules which bind to and surround the first ice crystals in the blood, preventing them from combining with others and leading to the solidly frozen state. In very small invertebrates, cells of their bodies get rid of almost all of their watery content when it gets cold and what is then left of their cell interiors has so little water in it that freezing does not occur and the cells can not expand and burst as it gets colder (ice expands as it gets colder: the famous anomaly of water!).

So, antifreezes do work, but from my visits to Antarctic I know that our men and women there would argue that a bottle of whisky (and rum in the case of my Jamaican friends) would also be quite effective against freezing to death – but they are totally wrong, of course. Why? Think about it: what colour does your skin get after a drink of whisky, vodka, or high percentage rum and what does that indicate with regard to your body heat conservation?

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For more reading about cold stories, click here for “Is winter making us stupid?

© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2016.
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.