Meeting Abstract
The simple behavioral repertoire of mussels includes gaping, which facilitates feeding and oxygen exchange, and possibly reorientation of the body posture via the foot and byssal system. Gaping behavior in subtidal habitats is often driven by external factors such as food availability, diel cycles, or predator presence. In intertidal habitats, where bivalves such as Mytilus californianus are repeatedly exposed to aerial conditions, valve closure can serve the additional function of limiting desiccation, although at the cost of a transition to anaerobic metabolism. Using an electronic datalogging system, we have tracked the valve gaping behavior, body orientation, and mantle cavity temperatures of mussels in different microhabitats on an open coast rocky shore. The predominant pattern in shell gaping is aligned with the circatidal rhythm for mussels living at two intertidal heights and for those in a tidepool. In microhabitats with longer submersion times, there is a secondary peak in gaping behavior more closely aligned with the diel cycle. Unlike some related mussel species, there is little evidence of valve gaping during peak low tide temperatures (31-38 °C), indicating that M. californianus may favor desiccation avoidance over evaporative cooling during thermal stress events. We observed minimal movement or re-orientation of focal mussels within our experimental beds over time scales of days to weeks, despite significant inter-individual variation in maximum body temperatures. When aligned with temperature records and physiological measurements, these monitoring data will allow us to estimate which environmental and behavioral factors contribute most to the physiological performance and survival of mussels living in highly variable intertidal environments.
