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, 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 with appropriate and specific direction to the original content.


Beauty and the Beast

When plants are not what they seem to be

While animals often have good reason to conceal themselves by assuming the colour and shape of the surrounding vegetation, in other words resembling plants, the opposite, namely plants resembling animals is much rarer. There are, however, some plants that are animal-like. Firstly, there are those which possess physiological or functional similarities to animals – and I am not talking here about fungi, mushrooms, yeasts and toadstools, which are not considered to be plants, but comprise a kingdom all by themselves. After all, they do not possess chlorophyll and cannot photosynthesize like plants, but they also do nit move around or reproduce like animals. Yet, they grow (or better “feed”) on organic matter just like animals, possess chitin like insects, and in some cases even possess the enzyme collagenase to digest collagen like animals. But, let’s turn to real plants resembling animals.

There are the sensitive plants like the mimosa, which move and react to touch and heat with a behaviour of some rapid folding and lowering of their leaves, a reaction that is even conducted along the stem to more distant parts of the plant. We can also think of certain fruits that will explode, spring open upon at the slightest touch to cast out their seeds and we must not forget the carnivorous plants, many of which like the famed Venus Fly Trap possess modified rapidly-closing leafy traps with serrated edges or, like the submersed pond bladderwort, operating with a suction device to pull in its prey. Others work with enticing drops of glittering glue ad tiny mobile “tentacles” on the surface of their leaves like the sundews or they developed pitfalls with slippery walls like the pitcher plants – all in order to boost nutrient intake with tissue from small animals, which these plants catch and are able to digest. In fact, the first scientific film I made when I worked for a year with the education channel of a TV company many years ago in Germany, had the title “Pflanzen, die von Tieren leben” (plants that prey on animals). That film also featured the small and endangered underwater version of the Venus Flytrap, known as Aldrovanda vesiculosa.

The most amazing animal-alike plants, however, are found in the second category: they don’t move, trap or digest animals, but they look like some. I am talking here not of cacti or the fruits of a chestnut tree, which resemble sea-urchins or miniature hedgehogs, but of the flowers of various orchids, which look remarkably similar to female wasps, bees, or beetles – depending on the species of orchid. These orchid flowers “mimic” the appropriate female insect to such an extent in shape, size, colour, and even scent that male insects are persuaded to attempt copulating with these dummy females of plant origin. By the time the fooled males have noticed their mistake, they have picked up some orchid’s pollen or left some from a previous encounter and, thus, help pollinating these “tricky” flowers, the “sirens” of the plant world. “Et Dieu… créa la femme”: appropriate not only in the human context.

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Click here to read more about explosive plants and animals!

© Dr V.B. Meyer-Rochow and, 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 with appropriate and specific direction to the original content.

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Something to remember

Some names you won’t forget

All life forms have a scientific name; in fact a double-name consisting of a specific and a generic component. It is by these names that scientists all over the world know precisely which organism is meant. In most cases these names have Latin or Greek roots. The housefly, for example, is Musca domestica, with Musca meaning ‘fly’ and domestica referring to the ‘home’, representing genus and species, respectively. There are other ‘flies’, also belonging to the genus Musca, but being different species they have different specific names like autumnalis or sorbens. Thus the full names of these flies would be Musca autumnalis and Musca sorbens (the generic name starts with a capital letter, the specific name with a small letter, but both are given in italics). Continue reading