Organism Physiology Paper: The Tardigrade

Organism Physiology Paper: The Tardigrade

Jarrod Scott

BIO/101

June 30, 2016

Mr. Whitbey

Organism Physiology Paper: The Tardigrade

When thinking of the world's toughest animals, most people picture obvious contenders for this title such as a lion. The lion is, of course, known as the king of the jungle. Or maybe a camel for its ability to thrive in the harsh temperatures of the desert and go days without water. In the same respect, the penguin may be thought of for its capability to withstand the extreme colds of the Arctic tundra.  However, none of these animals survivability can compare to that of a tardigrade. The tardigrade, though it is as small as the point of a pen, is one of the few animals that has survived the last five great extinctions. This tenacious microorganism can survive in such extreme conditions that no other creature can come close to matching its ability to thrive in the most inhospitable environments. In this paper, I will briefly describe the environment and the role of the tardigrade within it, identify the structures and functions of the main organs found in the tardigrade, explain how the tardigrade has evolved physiologically to become suited to its environment, and describe what would change if the tardigrade were to be transplanted to a significantly different environment.

                              [pic 1]

                                            Figure 1https://comicsagogo.files.wordpress.com/2013/02/tardigrade-big.jpg

       The tardigrade is a ubiquitous extremophile. They have been recorded in every biotope: both salt and fresh water; the humidity of rain forests, the altitude of mountains, the dryness of desserts, and the isolation of remote islands and Antarctic nunataks (Miller, 2007). Though they are found on every continent, all tardigrades are aquatic. They need to be in water to live, to find food, to breathe, to reproduce, and to move (Miller, 2007). The source of water can be as extreme as the deepest trenches of the ocean or the waters of Antarctica. However, most tardigrade species are terrestrial and live in moist habitats, such as soil and leaf litter or among mosses, lichens, liverworts, and cushion-shaped flowering plants (Nelson, 2015). Tardigrades are reported to feed on a broad range of food sources, including algae, fungi, rotifers, protozoa, bacteria and plant roots (Sanchez, Ferris, Gull, 2008). While scientist are still studying and learning about tardigrades, their effect on the ecosystem is poorly understood. Tardigrades aren’t known to cause disease or benefit humans in any concrete way, nor do they contribute to the ecosystems and environments they inhabit (Jarreau, 2013).

                           [pic 2]

                             Figure 2:http://studydroid.com/printerFriendlyViewPack.php?packId=467142

Scientists studying the tardigrades agree that the tardigrade somewhat resembles a panda bear, hence the nickname water bear. Their bodies consist of five sections, a well-defined head and four body segments, each of which has a pair of legs fitted with claws (Miller, 2007). Depending on the species, which there are roughly one thousand documented, they may or may not have eyes. However, their organs are incredibly similar. Their internal structure includes a full alimentary canal and digestive system but lacks circulatory or respiratory systems. This is due to the hemocoel-type of fluid-filled body cavity that functions in circulation and respiration (Nelson, 2015). An open hemocoel means that all gas exchange is done at the surface of the body. Their mouths are tubular and lined with stylets which can be used to pierce prey or plant cells. The mouth is also equipped with a sucking pharynx that allows the tardigrade to suck the juices from whatever it is eating. The pharynx leads to an esophagus, stomach, intestine, and anus (Miller, 2007). Muscles inside the tardigrade are all longitudinal and rely on hydrostatic pressure for articulation. Below the esophagus is the relatively large lobed dorsal brain.  The brain sits atop a double ventral nerve cord consisting of fused paired ganglia which runs the length of the body. Within the species, there are both male and females, but each only has one gonad.