title: No evidence for homeoviscous adaptation in intertidal snails: analysis of membrane fluidity during thermal acclimation, thermal acclimatization, and across thermal microhabitats.
abstract: Many eurythermal organisms alter composition of their membranes to counter perturbing effects of environmental temperature variation on membrane fluidity, a process known as homeoviscous adaptation. Marine intertidal gastropods experience uniquely large thermal excursions that challenge the functional integrity of their membranes on tidal and seasonal timescales. This study measured and compared membrane fluidity in marine intertidal snail species under three scenarios: (1) laboratory thermal acclimation, (2) thermal acclimatization during a hot midday low tide, and (3) thermal acclimatization across the vertical intertidal zone gradient in temperature. For each scenario, we used fluorescence polarization of the membrane probe DPH to measure membrane fluidity in individual samples of gill and mantle tissue. A four-week thermal acclimation ofTegula funebralisto 5, 15, and 25°C did not induce differences in membrane fluidity.Littorina keenaesampled from two thermal microhabitats at the beginning and end of a hot midday low tide exhibited no significant differences in membrane fluidity, either as a function of time of day or as a function of thermal microhabitat, despite changes in body temperature up to 24°C within 8 h. Membrane fluidities of a diverse group of snails collected from high, middle, and low vertical regions of the intertidal zone varied among species but did not correlate with thermal microhabitat. Our data suggest intertidal gastropod snails do not exhibit homeoviscous adaptation of gill and mantle membranes. We discuss possible alternatives for how these organisms counter thermal excursions characteristic of the marine intertidal zone.
authors.affiliation: Hopkins Marine Station, Stanford University, Oceanview Blvd., Pacific Grove, CA 93950 USA.
authors.forename: Amber
authors.initials: A
authors.lastname: Rais
authors.affiliation: Romberg Tiburon Center, San Francisco State University, 3150 Paradise Dr, Tiburon, CA 94920 USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Miller
authors.affiliation: Romberg Tiburon Center, San Francisco State University, 3150 Paradise Dr, Tiburon, CA 94920 USA ; Department of Integrative Biology, University of California Berkeley, 3060 Valley Life Sciences, Bldg #3140, Berkeley, CA 94720-2140 USA.
authors.forename: Jonathon H
authors.initials: JH
authors.lastname: Stillman