Learn more about the fascinating functions of hydrodynamic mechanisms and hydraulics in nature.

Fascinating Hydrodynamic Mechanisms

Posted: December 16th, 2009 | Filed under: Hydrostatic skeleton | Tags: , , , , , , | 1 Comment »

Animals can also make elective use of a hydrostatic skeleton, its main advantage being that it can be created for as long as it is needed. When it is no longer required, the pressure in the system can be reduced so that nothing remains of the skeleton. True enough, the hydrostatic skeleton is not as reliable as a bone one, and, where the supports have to be permanent, the hydrostatic skeleton has given way to more rigid constructions. But for non-permanent skeletons hydraulics has proved more advantageous. Nature has applied this invention throughout the history of the evolution of the animal kingdom, right from the lowest creatures up to the most developed ones, man included. Cavernous bodies employing blood as the working fluid is a good example.

Hydrodynamic mechanisms are still more fascinating. These range from extremely primitive devices to rather sophisticated ones. The most primitive of them include the excretory siphon-tube in bivalve mollusks. These living crea­tures derive oxygen and food, microscopic organisms and particles of plant and animal matter from the surrounding water, which they suck into the mantle cavity. The water saturated with carbon dioxide and polluted with excretory products is ejected through a special siphon-tube. The mollusk, no doubt, wishes the waste material to be removed far away from its body so that it would not return into its mantle cavity. This explains why the excretory siphon-tube is rather long, though it has no special muscle and cannot stretch. When the shell is closed and water stops moving into the mantle cavity, the siphon-tube con­tracts, but as soon as the fluid resumes its flow, the siphon straightens and stretches.

The hydrodynamic (water-vascular) mechanisms in the spider’s legs are concerned with locomotion. These eight-legged creatures whose legs consist of six or seven segments flex them, like all animals do, by contracting certain specific muscles, but extend them by increasing pressure within the chitin-clad legs.


Hypertension And Obturator Muscle Functions

Posted: December 14th, 2009 | Filed under: Extra unnatural functions | Tags: , , , , , , , | No Comments »

Nature is always striving to allot an organ certain extra unnatural functions. Although the duties of the cardiovascular system are very specific and highly responsible, it could not avoid this common plight since nature was eager to utilize the pressure in the circulation system.

Hypertension (abnormally high blood pressure) is known to be very dangerous for the organism as it may disturb the blood system and cause damage to the blood vessels. Nature, however, turned this phenomenon to advantage. Thus, the lizards, known as horned toads, inhabiting the deserts of Mexico, use the local hypertension in the blood vessels of the head as a means of defence.

Generally speaking, this phenomenon is not terribly uncommon. When the blood, under abnormally high pressure, enters the crests, spines, and other outgrowths on the head and the body, they expand, straighten out, change colour and make the animal look fearful.

This is not the only means of defence of horned toads. Nature supplied them with a wonderful mechanism: when the lizard is standing at bay, a specific muscle, known as the obturator muscle, presses against one of the major blood vessels, markedly raising the pressure in the blood vessels in the head; it proves too high for the delicate vessels in the nictitating membrane and they rupture squirting blood into the face of a predator. This unexpected shower often makes the intruder take flight. This weapon is operative within the radius of one and a half metres.

The other function of the obturator muscle is connected with moulting. The reptiles continue growing throughout their lives. Horned toads change their skin every year. Casting oil one’s clothes can sometimes be difficult. This is where the obturator muscle comes into play. When the pressure in the head vessels increases, all the blood vessels, major and minor, distend and the head expands, tearing the old skin. When the skin on the head has ruptured, the lizard simply crawls out of it through the newly formed opening.