Galloway, AaronMunger, LisaEmlet, RichardBaki, Zane2023-08-182023-08-182023https://hdl.handle.net/1794/2864924 pagesThe purple urchin (Strongylocentrotus purpuratus) is a prominent grazer on the Oregon coast that has helped create and maintain urchin barrens by preventing the re-establishment and growth of new kelp. Urchins have 4 different types of pedicellariae on their tests: globiferous, tridentate, triphyllous, and ophicephalous (Coppard et al. 2012). Tridentate pedicellariae prevent the settling of any unwanted organisms on the urchin’s test. With the notion that biodiversity and species richness is lower at jetties, it was hypothesized that urchins from a natural intertidal would have a higher number of pedicellariae due to having more organisms to fend off from settling. 100 urchins were collected, 50 from South cove, Cape Arago, and 50 from a jetty near OIMB. Urchins were taken into a lab and frozen in order to keep them intact before counting pedicellariae. A dissection scope was used to count aboral tridentate pedicellariae, and the diameter of each urchin was then measured and used to calculate the area of the urchin’s aboral surface. Pedicellariae per mm2 (ped/mm2) was generated for each urchin before being averaged out and plotted on a column graph with Standard Error (SE) being plotted as error bars. The average pedicellariae per mm2 of urchins from South Cove was 0.0309 ± 0.001 and the average of urchins from the OIMB jetty was 0.0309 ± 0.001. Potential future studies include looking at different types of pedicellariae with a similar question or how densities change between environment types.en-USCC BY-NC-ND 4.0purple urchinpedicellariaetridentatedensitydifferent environmentThesis/Dissertation0009-0006-0938-9712