Rheology of Naturally Deformed Antigorite Serpentinite: Strain and Strain‐Rate Dependence at Mantle‐Wedge Conditions

Antigorite serpentinite is expected to occur in parts of subduction plate boundaries, and may suppress earthquake slip, but the dominant deformation mechanisms and resultant rheology of antigorite are unclear. An exhumed plate boundary shear zone exposed near Nagasaki, Japan, contains antigorite deformed at 474°C ± 30°C. Observations indicate that a foliation defined by (001) crystal facets developed during plate-boundary shear. Microstructures indicating grain-scale dissolution at high-stress interfaces and precipitation in low-stress regions suggest that dissolution-precipitation creep contributed to foliation development. Analysis of crystal orientations indicate a small contribution from dislocation activity. We suggest a frictional-viscous rheology for antigorite, where dissolution-precipitation produces a foliation defined by (001) crystal facets and acts to resolve strain incompatibilities, allowing for efficient face-to-face sliding between facets. This rheology can not only explain aseismic behavior at ambient plate boundary conditions, but also some of the contrasting behaviors shown by previous field and laboratory studies

Behavioral and respiratory responses to stressors in multiple populations of three-spined sticklebacks that differ in predation pressure

Individual animals of the same species inhabiting environments which differ in the frequency and magnitude of stressors often exhibit different physiological and behavioral responses to stressors. Here, we compare the respiratory response to confinement stress, and behavioral responses to ecologically relevant challenges among sticklebacks from 11 different populations varying in predation pressure. We found that sticklebacks from high predation populations breathed faster in response to confinement stress and were, on an average, more behaviorally responsive to a pike behind glass compared with sticklebacks from low predation populations. These patterns differ from the results of studies on other species, highlighting the need for a conceptual framework to understand the proximate and ultimate factors shaping variable responses to stressors over developmental and evolutionary time. Moreover, physiological and behavioral responses were integrated with each other, both at the individual and population levels. In general, fish that were more aggressive and bold in the presence of a predator breathed faster, independent of body size. These results are consistent with the growing body of evidence that individuals differ in a suite of physiological and behavioral mechanisms for coping with challenges in the environment

Effects of Parasitic Crustacea on Hosts

This chapter summarises our understanding of the direct effects that parasiticcrustaceans have on their invertebrate and vertebrate hosts. At the individual hostlevel, the effects of infection with parasitic Crustacea with respect to host pathologicalchanges and the development of disease states are reasonably well understood. However,we have a much poorer understanding of how infection affects the physiological,immunological and reproductive status of hosts, with much of what is known arisingfrom studies of sea lice (caligid copepods) infections of salmonids. Quantifyingsublethal impacts of parasitic Crustacea infection on the biology and ecology of hostsis especially challenging even under controlled laboratory conditions. This is due to thecomplex and poorly understood interactions between parasite, host and environmentaldeterminants, which ultimately influence the outcome and magnitude of the effect.There is very limited information on the effects that parasitic Crustacea have on theirhosts at a population level, as well as on the indirect effects that they may have onspecies that interact with their hosts (community level effects). Our relatively goodunderstanding of effects of sea lice on salmonids has been brought about due to thelarge economic impact that these parasites have on farmed salmonids and the necessityto develop new methods for their control. Unfortunately, the progress for other parasitesand hosts is much slower which is in part due to the lack of experimental systems,research tools and funding