(full paper is archived in the Miller Library)
Title: Variation in the growth and physiology of Mytilus californianus from Central Oregon and Central California
Student Author(s): Roth, Melissa S.
Faculty Advisor(s): Somero, George
Location: Final Papers Biology 175H
Date: June 2001
Abstract: Mytilus californianus dominates the rocky mid-intertidal zone along much of the West Coast of North America from Alaska to Baja California. Thus, it has important effects on community structure. Previous work has failed to identify genetic differences among populations along this latitudinal gradient. However, some differences in morphology have been described. A preliminary study showed that mussels from Central Oregon grew significantly faster than those from Central California when transplanted to sites in either state. My study investigated physiological differences in populations of M. californianus from Oregon and California. In February, mussels were transplanted to California from Oregon and California. In May, additional mussels were freshly collected from the original populations. Gill respiration rates and malate dehydrogenase (MDH) activity were examined to compare metabolic rates of individuals in these populations, and determine if differences were intrinsic or transitory effects of acclimation.
No significant differences were found in respiration rates or MDH activity between the two populations of mussels, both for field acclimated and freshly collected groups. Although overall field growth was low, there was suggestive but inconclusive evidence that transplanted mussels from Oregon grew significantly more than California mussels during the February to May period. These results do not rule out either an acclimation effect or intrinsic differences between these populations. Because the Oregon waters were slightly colder (by 2.5º C) during the ten weeks prior to the transplantation, acclimation of the Oregon mussels may explain the growth difference. Alternatively, there could be intrinsic differences in growth potential between the two populations. In either case, differences in respiration rates and MDH activity were either too small to be detected, or may not be directly correlated with growth activity. Although physiological differences were not observed, there appear to be some differences among these mussel populations such as the average dry weight of gills from Oregon mussels was 16.9% less than the average weight of similarly sized California mussels.