Making its way through the Cambrian to the present, Tardigrata, colloquially known as the Water Bear, is the only creature which could survive extreme conditions – even the usually deadly outer space! Reaching merely a centimetre in length, the barrel-shaped micro-animal has four pairs of stumpy limbs. Therefore, this water-dwelling animal is also nicknamed the Slow Stepper.
To decrypt the cipher of the Water Bear’s stunning survival skills, in September 2007 the European Space Agency conducted a bio-experiment during the FOTON-M3 space mission. In the weightless environment, a series of biological processes, for instance, cell multiplication, tissue regeneration and genetic activities of Water Bear, were clearly inspected. The unprecedented conclusion proves that the organism can not only get through the extreme conditions of zero air pressure and cosmic rays for ten days, but also regenerate on its journey back to Earth.
The Water Bear has walked through thousands of millennia from the Cambrian Period through its remarkable reproductive traits. Depending on the conditions, Water Bear could be flexible in reproduction – multiplying itself in either heterologous or homologous ways. The former relies on external fertilisation after the female lays eggs, while the latter is simply a split of the female’s self.
Belly-up? They Are Waking Up!
Scientists in Japan revealed that Tardigrades could withstand starvation and freezing temperatures for 30 consecutive years. Cryptobiosis, a metabolism suspension ability through cutting water content, sheds light on this survival secret. When the environmental condition returns to normal, they revive themselves by restarting the metabolism. Therefore, the adaptive creature could hardly be defeated by exposure to extremely high or low temperatures, deadly radiation and changes in gravity.
Yet, the extraordinary resilience does not really indicate the survival master’s living preference. In Hong Kong, Water Bears mainly inhabit the upper courses of streams, especially on Tai Mo Shan. Freshwater streams, lake sediments and stone mosses are their favoured locations, which are rich in sap from algae, mosses and lichen, as well as other microorganisms to prey on, even though Water Bears also have a cannibal nature.
The awe-inspiring adaptation of Tardigrades drives scientists to learn more about their genetic structure. Uncovering the survival mechanism of Water Bears under intense radiation could be critical to mitigating health risks that X-rays pose to humans. Never look down on the little ones; each step of studying Tardigrades may make significant contributions to scientific development.