Crayfish And Starfish Similarities

This last month, in AP Biology, the class completed the dissection of a starfish, followed by a crayfish. With the experience of these labs, comparisons can be made between many aspects of these two organisms. These aspects suited for comparison include the body plans and symmetry of starfish and crayfish, the science behind their need and ability to move, how each organism obtains oxygen and distributes it therefore throughout the body, the processes of their digestive and nervous system, and lastly how each organism reproduces and the pros and cons of their methods.
Starfish are classified among the phylum Echinodermata and are an invertebrate with radial symmetry and an internal skeleton with hard external spines. They have five arms, their …show more content…
As their skeletal systems differ, their muscle location and distribution differs as well. Crayfish have more joints, working together with muscles, enabling more movement than starfish (Muscles Anatomy Neal Pearce). By having more joints crayfish are able to move efficiently both on land and in water. In terms of efficiency however, starfish are able to get their job done as well by using its hydraulic system found in its limbs which takes in water from the surface the starfish would like to adhere to, creating a sealed suction, and releasing the water taken in to become unattached (Starfish). The starfish also uses its tube feet for moving around (Echinoderms). These differentiable characteristics are an advantage to each specific organism however aren’t necessarily characteristics which could be said would be an advantage for every organism to have. Having an endoskeleton and hydraulic system is suitable for a starfish in their lives and despite not having a hard shell they have chemicals inside of them to protect against predators and some have spines around them (Starfishfacts). Crayfish on the other hand, have a harder body, claws, and legs making it more mobile and supplying it with suitable characteristics for fulfilling its lifestyle …show more content…
Starfish use their tube feet to take in oxygen and release carbon dioxide. From the tube feet the oxygen goes through its fluid filled gas canals (hydraulic system) and distributes oxygen throughout the starfish’s blood and body. In addition, starfish do not have hearts and their blood is not always pigmented (Echinoderms). Crayfish, in comparison, have a heart and gills, which in some cases enable them to breathe on land and in water. When water goes through the gills, the oxygen gets transferred into the bloodstream and the carbon dioxide is then released. In cases of breathing on land, some crayfish have made the adaptation of excreting a liquid onto their gills when out of the water (Writer, L.