Meeting Abstract
The giant acorn barnacle, Balanus nubilus, has the largest muscle fibers in the animal kingdom (diameters can be > 3mm in adults). At these sizes, muscle cells are at risk for insufficient oxygen delivery owing to low SA:V ratios. This challenge may be exacerbated during low tide air emersion or environmental hypoxia, when hemolymph oxygen levels are predicted to drop. Barnacles, however, are particularly successful at acquiring oxygen and maintaining similar rates of aerobic metabolism under both aquatic and terrestrial conditions. We are interested in whether B. nubilus possesses these abilities given the potential metabolic limitations of their giant muscle fibers. We investigated the respiratory behaviors (% time aperture open, cirri beat frequency) of B. nubilus, during acute (6h) exposure to normoxic immersion, air emersion, and anoxic immersion. Further, we compared oxygen consumption rates (MO2; via intermittent respirometry) of barnacles in water (10, 15, 20°C) and in air (15, 20°C). Preliminary data revealed that B. nubilus have a significantly higher cirri beat frequency and % time aperture open (with cirri extended) during normoxic immersion than anoxic immersion, though these values are not significantly different from animals held in the air. This suggests that B. nubilus does engage in behaviors aimed at increasing oxygen uptake while out of the water, but remains relatively inactive during anoxia. Based on this, we predict that MO2 values for B. nubilus will be similar in water and air. To date, we have found a significant linear relationship between temperature and MO2 in the aquatic realm – as we would expect for an ectotherm – and we are still collecting our terrestrial MO2 values.
