DEFENSE MECHANISMS IN NATURE

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Excerpted from Flaws in the Theory of Evolution by Evan Shute, Craig Press: New Jersey (1961)

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Eremnophila aureonotata transporting a paralysed prominent caterpillar to the nest she has excavated

The Hunting Wasp carries a director in its tail which has a tiny point with a hole in it through which two lancets shoot out to sting its prey. These needles are three-sided, their outer V-shaped edge retained in a slot on the inner wall of the director. The inmost sides of the two needles in the centre are concave, forming a poison tube. The extremities of the needles are also barbed with six flat barbs and at the base of each barb a channel is cut through into the central pipe. This lets the poison squirt out of the end of the pipe and through the sides at the base of the barbs. What a magnificent weapon to evolve piece-meal!

The cockroach, Diploptera punctata, has a defensive spray it can eject from only one side of the body or from both; it can aim this spray, can use it up to four discharges at a sequence, and by this means can repel attacking ants and carabids and temporarily palsy them. Diploptera punctata also produces a nutritionally dense crystalline “milk” to feed their live-born young.

The Malayan hooded locustid (Capnoptera) does not resist when picked up, casually lowers its head, opens a cleft between its head and thorax, thus forcing out a scarlet bladder or hood, as if its entrails were extruding in a frightening way. The Singhalese grasshopper, Acridium violescens, if chased by Mynah birds, rolls over on one side, and deliberately draws up a hind leg to expose a series of grey and black eye-spots. The bird usually withdraws, even after several approaches. The rolling over is done deliberately and slowly. How could such an unusual habit evolve to reveal the warning colour pattern so perfectly? How did the insect know it was there, and could be menacing? The mantids also reveal menacing bright colours and make a noise when attacked. Their predators show fright,—as do humans, indeed.

An Australian worm, Didymogaster silvaticus, when handled roughly, squeezes itself and shoots a fluid out of some 20 perforations in its body to a height of perhaps four feet.

The sloth of tropical forests is often coloured green because a symbiotic green alga lives in its grooved hairs and gives this protective colouring to its host. Put the sloth in a zoo and its colour fades as the alga dies. How prescient of the sloth to provide these unique grooved hairs! How wise of it to let only a green fungus live in the grooves! How accommodating of the fungus!

Tinbergen quotes Kepner from Lashley on the adaptations of Microstoma: “Microstoma, related to the more familiar Planaria and liver flukes, is equiped with nematocysts or stinging cells like those of the hydroids, which it discharges in defense and in capture of prey. In discharging, the stinging cell evaginates a threadlike, barbed tube through which poison is ejected. The striking fact about the creature is that it does not grow its own weapons, but captures them from another microscopic animal, the fresh-water polyp, Hydra. The Hydras are eaten and digested until their undischarged stinging cells lie free in the stomach of Microstoma. The nettles are then picked up by amoe­boid processes of the cells lining the stomach and passed through the wall into the mesoderm. Here they are again picked up by wandering tissue cells and carried to the skin. The stinging cells are elliptical sacs with elastic walls, which are turned in at one end as a long coiled tube. In discharging, the wall of the sac contracts and forces out the barbed poison tube from one end of the sac. The nettle cells can therefore fire in only one direction. When the mesodermal cell carries the nettle to the surface, it turns it around so as to aim the poison tube outward. It then grows a trigger, and sets the apparatus to fire on appropriate stimulation.

“When Microstoma has no stinging cells it captures and eats Hydra voraciously. When it gets a small supply of cells these are distributed uniformly over the surface of the body. As more cells are obtained they are interpolated at uniform intervals between those already present. When a certain concentration of cells is reached, the worm loses its appetite for Hydras, and, in fact, will starve to death rather than eat any more of the polyps, which are apparently not a food but only a source of weapons.

“Here in the length of a half a millimetre, are encompassed all of the major problems of dynamic physiology.” Indeed, the whole process is simply incredible, on an evolutionary basis.

In the Nematode life-cycle there is an abrupt change in the third-stage larva, in many forms, from an aerobic to an almost anaerobic environment, and from a metabolism depending on the catabolism of fat to one mainly depending on glycolysis, and from a free life to a parasitic one.

The biochemist will be puzzled by this.

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