Jonathan Robinson Marine and Estuarine Science Program  Department of Biology   B.A. Marine Science, University of Hawaii at Hilo, 2005. MSc completed Spring 2009

Project:   The effects of simulated wave force on the metabolism of the rough keyhole limpet Diodora aspera

Abstract: Organisms living in the intertidal zone face a myriad of changes on a daily basis and an important aspect of understanding the biology of intertidal animals is to determine how they respond physiologically to environmental parameters. Wave force is an important environmental parameter that might potentially place high energetic demands on intertidal animals. The Rough Keyhole Limpet, Diodora aspera, lives in areas of high water flow and can use external water flow to increase the amount of water passing over its gills due to the hydrodynamic induction of water flow, or induced flow, through its mantle cavity. This augments ciliary-induced currents and may increase aerobic metabolism. Thus, D. aspera is an ideal organism with which to study the metabolic costs and benefits of living in a wave-swept habitat. I initially adapted a novel mask-system to determine oxygen consumption of this limpet. The mask-system measures the oxygen level of the water exiting the apical hole in the shell. Baseline oxygen consumption of D. aspera was measured using closed-system respirometry and compared to oxygen consumption measured with the mask-system. Resting oxygen consumption, measured in closed-system respirometer, increased with increasing limpet mass and was described by the equation: VO2 = 1.5 M^0.71. Limpet oxygen consumption in the closed respirometry system was significantly higher than that of the same limpets using the mask respirometry system, with limpets having on average 57% higher oxygen consumption in the closed system. Next, the metabolic response of limpets to varying induced flows was determined. In the mask respirometry system, as induced flow rates increased the oxygen consumption of individual limpets also tended to increase and appeared to level off at approximately 30 mL min^-1 for most limpets. Finally, I performed laboratory experiments that simulated hydrodynamic forces on D. aspera to examine the effects of wave force (0N, 0.8N, 1.6N, 3.2N) on D. aspera’s oxygen consumption. Wave force had no statistical effect on D. aspera’s aerobic metabolism. There was a slight trend that oxygen consumption increased from the resting rate when wave force commenced, although variability was high. Since living in this wave-swept environment is not as metabolically taxing as I hypothesized, D. aspera may derive a metabolic benefit from living there by relying on water flow to enhance its respiratory gas exchange. The cost of adhesion during wave exposure may be offset by the increased oxygen availability and increased in aerobic metabolism D. aspera would derive from water flow.
GK-12 Fellowship