Tardigrades also called Water bears or Moss Piglets are aquatic microscopic invertebrates that can grow up to 1mm in length. They were discovered by a German Pastor in 1773.They move very slowly in their habitats giving them the name Tardigrade (slow moving). These animals are eight legged (4pairs) each having four to eight claws. They have short, plump bodies and scrunched-up heads. The mode of reproduction in these animals is both asexual (parthenogenesis) and sexual. More than 1000 species of the phylum Tardigrada have been identified. Ramazzottius variornatus is considered to be the toughest and most resilient of all the species found.
These tiny, strange and cute animals are un-destroy-able and have the ability to survive in extreme conditions such as boiling hot springs and even under layers of ice though their general habitats are sediments at the bottom of lakes, moist piece of moss and other wet environments. They can withstand temperatures from -328°F to 300°F. Tardigrades have the ability to even withstand radiations, high amounts of pressure as well as vacuum of space. When the European Space Agency sent some species of Tardigrade into the lower Earth orbit in 2007, they were able to survive for 10-12 days outside the capsule though they were exposed to space vacuum and radiations.
Water bears can survive complete dehydration by undergoing anhydrobiosis (a desiccated dormant state). Tardigrades curl up into a dry lifeless ball like structure called a tun, with reduced metabolic activity during stress conditions. Once re-hydrated it returns to its normal metabolic form within few hours. Scientists identified a set of proteins that seem to replace the water lost by Tardigrades during anhydrobiosis and maintain the microscopic structure until water is available again. Tardigrades also carry a certain set of genes that help protect their DNA from damage during stress conditions. They lack stress sensing pathways and hence do not die during damage; an alternative pathway where the proteins make repairs is prevalent.
Since they are slow walkers and are not dynamic, they do not have competitors for food. They feed on algal, lichen and moss juices to survive. Few species act as carnivores and some even cannibals where they feed on other Tardigrades. Due to their ecological incompetence they have been able to acquire extreme survival abilities. Due to such varied survival strategies developed by these tiny creatures it is believed that Tardigrades might even survive after humanity is long gone.
Artile by Vidya.