Methods Essays - Littorinidae, Common Periwinkle, Periwinkle

Methods The purpose of this experiment is to test how periwinkles react in different salinities by measuring their overall velocity (movement over time). We set up two containers of the same volume each with the same volume but different levels of salinity, and would individually subject one periwinkle to one of the salinities, thus creating a separate experiment with two treatments (one of 10ppt, one of 30ppt). The periwinkles were chosen at random by a rotation of selectee that was determined by both a 6-sided die and a coin flip. Once the periwinkles were introduced and were both right side up a 30 second acclimatization period would begin. After that 30 second period, had elapsed a secondary timer of five minutes would begin. During these five minutes, two randomly chosen members of the group would trace the Periwinkles movement on a clear plastic sheet with an erasable marker. A secondary sheet of clear acetate was provided should the Periwinkles start to climb on the walls of the conta iner. After five minutes, the periwinkle form each container was removed and placed in a "used" container. The used periwinkles would not be taking part in the rest of the experiment. This was repeated as time permitted allowing for roughly 10 replicates within each trial. Pictures were taken of the traced movement and then the process would begin again. There were no adjustments made between trial 1 and trial 2. The periwinkles that we were used were randomly selected via die and coin combination that both randomized those that were picking (at random) as well as which jar the animal was being selected from. This was done in attempts to sample from a variety of the periwinkle population in efforts to avoid bias. The periwinkles were all collected at tower beach at random. In an effort to limit experimental uncertainty we made sure to roll die and flip a coin to decide the group and then the subsequent person who would be performing each task. Containers were emptied washed and scrubbed before being used again. This was to wash the mucus layer off of the container that other periwinkles might follow. To limit extraneous variables, temperature, salinity, and light was measured every three replicates to ensure there was no change in abiotic conditions. Human interaction was necessary in this case but was attempted to stay limited by not moving while observing the snail's movements. We used image J, an online software, to calculate the total distance travelled by analyzing the pictures of the plots we traced of the snail's movement. This in turn would provide us with a total distance that the Periwinkles travelled, which when divided by the time that we recorded for each replicate (five minutes) we received velocity which we could use to achieve our purpose.