Meeting Abstract

P1.141  Friday, Jan. 4  Effects of temperature on ouabain-insensitive ATPase activity in tube feet of northern and southern populations of the sea urchin Arbacia punctulata CURRIE, A/E*; PODOLSKY, R/D; University of Maryland, College Park acurrie@umces.edu

Changes in ocean temperature are expected to have widespread effects on biological processes. Identifying temperature-sensitive processes that are critical to function is important for understanding both patterns of geographic variation and future responses to climate change. Population comparisons offer a way to examine past responses to temperature and other abiotic factors along a latitudinal gradient. We focused on enzymatic activity in tube feet of the sea urchin Arbacia punctulata, in particular the effects of temperature on the activity of Na+K+-ATPase. This enzyme can be responsible for a substantial (25 to 40%) portion of the total energy budget and tube feet are one of the most metabolically active tissues in the sea urchin body. We compared northern (Woods Hole, MA) and southern (Charleston, SC) populations that were collected and held at temperatures differing by about 10ºC. Assays on tissue homogenates were run with and without ouabain, a glycoside known to specifically inhibit Na+K+-ATPase activity, to measure the contribution of this enzyme to total ATPase activity. Across a range of concentrations (0.1 to 16 mM) ouabain showed little to no effect on ATPase activity. Total activity for both northern and southern animals increased linearly as a function of assay temperature. Contrary to our predictions, at any given temperature ATPase activity standardized per unit protein was higher in the southern population, although when standardized per unit tube foot surface values were more similar. These data suggest that populations at colder temperatures may be less equipped to maintain adequate levels of ATPase activity in metabolically active tissue and may be most sensitive to anticipated temperature increases.