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RESEARCH COMPARATIVE PHYSIOLOGY OF OSMOTIC STRESS TOLERANCE
One of the
long-term research interests of the Galvez laboratory is the
comparative physiology of osmoregulation in teleost fish. Salinity
represents one of the most important barriers restricting the
distribution of aquatic animals. Some species can change their
phenotype to compensate for broad changes in environmental salinity,
whereas other species have narrow salinity tolerance ranges (Prodocimo
et al., 2007; Whitehead et al., In press; Whitehead et
al., submitted). We are currently funded by the National Science
Foundation, in collaboration with Dr. Andrew Whitehead (LSU), to
study the physiological responses and the genomic underpinnings of
osmotic stress in natural populations of Fundulus.
The transporting
epithelia of euryhaline fish are capable of a high degree of
physiological plasticity to environmental and physiological
stressors. We have shown that, depending on species, the gill
epithelium of fish may possess several subtypes of ion- transporting
cells known as mitochondrion-rich cells, and that these cells may
have different functions in whole-animal ion and acid-base
regulation (Galvez et al., 2006; Galvez et al., 2008b; Parks et al.,
2010. Current studies are continuing to investigate the cellular
and molecular mechanisms of ion and acid-base regulation in whole
animals, isolated epithelial preparations, and dispersed cells. We
are also describing the integrative analysis of key ion transport
proteins in transporting epithelia of F. grandis during
osmotic stress. This work has been funded by Oak Ridge Associated
Universities and from the LSU Faculty Research Grant program have
been used to investigate the cellular distribution of ion and metal
transport in the fish gill of euryhaline fishes. Freshwater unionid
mussels are the most endangered animals in North America, with more
than 70% of the approximately 300 species considered threatened or
endangered. Although the causes of this loss in biodiversity are
varied, the inability of larvae (i.e., glochidia) to undergo
metamorphosis on fish hosts contributes to this decline. Glochidia
primarily attach to the gills of fish, where they become
encapsulated within cysts by the surrounding epithelium. We
currently have funding through the Louisiana Board of Regents and
the Office of Environmental Education to study this host-ectoparasitic
interaction. Current studies are attempting to elucidate the
mechanisms of host physiology critical to glochidia survival
following attachment. We are also examining the cellular
composition of the cyst that encapsulates the glochidia during
attachment in order to understand the factors stimulating gill
remodeling to glochidia infection. i. Trace metal homeostasis and toxicity Trace metals are common constituents of biological systems, playing important roles in various regulatory and catalytic processes. Despite their physiological functions, high enough concentrations of metals interfere with ionoregulatory processes at the biological surfaces of aquatic animals. I have previously shown that water chemistry can influence the bioavailability and toxicity of a metal to fish by affecting its chemical speciation, which in turn affects how “strongly” a metal can interact with ion transport proteins. Conversely, little is known on how alterations in the physiology of an aquatic animal will influence the efficacy of metals on biological membranes. We have recently shown that physiological perturbations affecting ion transport proteins at the fish gill, will also affect the ability for metals to bioaccumulate (Galvez et al., 2007; Galvez et al., 2008a). We have continued interests in using cell physiological approaches and surrogate gill models to study the effects of physiology on metal bioavailability. Current projects are funded by the Environmental Protection Agency and the Department of Justice to study the toxic effects of metal effluents in receiving waters within Louisiana. ii. Effects of the Deepwater Horizon oil spill on resident marsh fishes In response to the Deepwater Horizon oil spill, my research group quickly mobilized and collected tissue and water samples from seven sites along the northern Gulf of Mexico, both before and after the oil hit coastal Gulf of Mexico marsh habitats. We have since received funding from BP Exploration and Production to assess the immediate and long-term effects on resident fish populations. Our goal is to characterize the time course of toxicity/stress response in situ in the gulf killifish, specifically documenting protein-level effects in osmoregulatory organs, including the gills, intestines, and kidneys. Water collected from these sites is being used to characterize the time course of effects in embryos and larvae of gulf killifish. Dr. Whitehead, a collaborator on the grant, is also utilizing tissues for transcriptomics to infer mechanisms of effect. Detailed hydrocarbon chemistry of water, sediment, and whole bodies is being conducted by Dr. Ed Overton (LSU) and remote sensing data provided by Dr. Nan Walker (LSU) to link environmental chemistry of actual exposure with biological effects’ data. More recently, my laboratory has received additional funding to characterize genomic and protein- level effects in Fundulus grandis from 15 oiled or reference sites within Barataria Bay, LA. In addition to assessing these field-sampled fish, we are also collecting juvenile fish from the field, and transporting them back to LSU, where they will be used for assessment of physiological performance. Our goal is to investigate the ability of fish to compensate for, and acclimate to, crude oil, linking effects from the molecular level to physiological performance. |
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