Craig Young Aaron GallowaySanchez-Reddick, Carmen Theresa2022-09-282022-09-282022-05https://hdl.handle.net/1794/2752726 pagesWhile the larval and early juvenile stages of the stalked ascidian Boltenia villosa are well documented in the literature, little is known about the range of morphological variation in the adults. Anecdotal evidence suggests that larger individuals with short stalks make up the populations found in Washington, while Oregon populations consist of smaller individuals with longer stalks. The present study aimed to develop a qualitative understanding of the morphological and reproductive differences across the latitudinal gradient of Boltenia villosa. This was achieved by using a combination of morphometrics and scanning electron microscopy to determine any significant differences between different populations and the use of oocyte diameter and dissections to compare reproductive output. The results suggest a significant morphological and reproductive difference between the two populations in body proportions and spine character despite their genetic similarities. These preliminary results indicate the possible existence of an undescribed subspecies of Boltenia villosa, but more research into the morphological changes across the entire range of each morphotype's range are needed.enCreative Commons BY-NC-ND 4.0-USMarine BiologyAscidian Boltenia VillosaSea SquirtMorphological VariationOocyte DiameterMorphometricsGonadosomatic IndexScanning Electron MicroscopyMolecular AnalysisThesis / Dissertation