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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.



REMODELING OF TRANSPORTING EPITHELIA IN RESPONSE ENVIRONMENTAL AND PHYSIOLOGICAL STRESS

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.



FISH GILL REMODELING DURING ECTOPARASITIC INFECTION

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.



PHYSIOLOGICAL RESPONSES OF FISH TO ENVIRONMENTAL TOXICICANTS

            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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Site last updated: 2013-05-23