Hypoxia-induced gene expression profiling in the euryoxic fish Gillichthys mirabilis

Hypoxia is important in both biomedical and environmental contexts and necessitates rapid adaptive changes in metabolic organization. Mammals, as air breathers, have a limited capacity to withstand sustained exposure to hypoxia. By contrast, some aquatic animals, such as certain fishes, are routinely exposed and resistant to severe environmental hypoxia. Understanding the changes in gene expression in fishes exposed to hypoxic stress could reveal novel mechanisms of tolerance that may shed new light on hypoxia and ischemia in higher vertebrates. Using cDNA microarrays, we have studied gene expression in a hypoxia-tolerant burrow-dwelling goby fish, Gillichthys mirabilis. We show that a coherent picture of a complex transcriptional response can be generated for a nonmodel organism for which sequence data were unavailable. We demonstrate that: (i) although certain shifts in gene expression mirror changes in mammals, novel genes are differentially expressed in fish; and (ii) tissue-specific patterns of expression reflect the different metabolic roles of tissues during hypoxia.

Contaminant bioavailability in soils, sediments, and aquatic environments

The aqueous concentrations of heavy metals in soils, sediments, and aquatic environments frequently are controlled by the dissolution and precipitation of discrete mineral phases. Contaminant uptake by organisms as well as contaminant transport in natural systems typically occurs through the solution phase. Thus, the thermodynamic solubility of contaminant-containing minerals in these environments can directly influence the chemical reactivity, transport, and ecotoxicity of their constituent ions. In many cases, Pb-contaminated soils and sediments contain the minerals anglesite (PbSO4), cerussite (PbCO3), and various lead oxides (e.g., litharge, PbO) as well as Pb2+ adsorbed to Fe and Mn (hydr)oxides. Whereas adsorbed Pb can be comparatively inert, the lead oxides, sulfates, and carbonates are all highly soluble in acidic to circumneutral environments, and soil Pb in these forms can pose a significant environmental risk. In contrast, the lead phosphates [e.g., pyromorphite, Pb5(PO4)3Cl] are much less soluble and geochemically stable over a wide pH range. Application of soluble or solid-phase phosphates (i.e., apatites) to contaminated soils and sediments induces the dissolution of the “native” Pb minerals, the desorption of Pb adsorbed by hydrous metal oxides, and the subsequent formation of pyromorphites in situ. This process results in decreases in the chemical lability and bioavailability of the Pb without its removal from the contaminated media. This and analogous approaches may be useful strategies for remediating contaminated soils and sediments.

Evolution and divergence of sodium channel genes in vertebrates

Invertebrate species possess one or two Na+ channel genes, yet there are 10 in mammals. When did this explosive growth come about during vertebrate evolution? All mammalian Na+ channel genes reside on four chromosomes. It has been suggested that this came about by multiple duplications of an ancestral chromosome with a single Na+ channel gene followed by tandem duplications of Na+ channel genes on some of these chromosomes. Because a large-scale expansion of the vertebrate genome likely occurred before the divergence of teleosts and tetrapods, we tested this hypothesis by cloning Na+ channel genes in a teleost fish. Using an approach designed to clone all of the Na+ channel genes in a genome, we found six Na+ channel genes. Phylogenetic comparisons show that each teleost gene is orthologous to a Na+ channel gene or gene cluster on a different mammalian chromosome, supporting the hypothesis that four Na+ channel genes were present in the ancestors of teleosts and tetrapods. Further duplications occurred independently in the teleost and tetrapod lineages, with a greater number of duplications in tetrapods. This pattern has implications for the evolution of function and specialization of Na+ channel genes in vertebrates. Sodium channel genes also are linked to homeobox (Hox) gene clusters in mammals. Using our phylogeny of Na+ channel genes to independently test between two models of Hox gene evolution, we support the hypothesis that Hox gene clusters evolved as (AB) (CD) rather than {D[A(BC)]}.

Comparison of aquatic food chains using nitrogen isotopes.

Recent studies have shown the utility of delta(15)N to model trophic structure and contaminant bioaccumulation in aquatic food webs. However, cross-system comparisons in delta(15)N can be complicated by differences in delta(15)N at the base of the food chain. Such baseline variation in delta(15)N is difficult to resolve using plankton because of the large temporal variability in the delta(15)N of small organisms that have fast nitrogen turnover. Comparisons using large primary consumers, which have stable tissue isotopic signatures because of their slower nitrogen turnover, show that delta(15)N increases markedly with the human population density in the lake watershed. This shift in delta(15)N likely reflects the high delta(15)N of human sewage. Correcting for this baseline variation in delta(15)N, we report that, contrary to expectations based on previous food-web analysis, the food chains leading up to fish varied by about only one trophic level among the 40 lakes studied. Our results also suggest that the delta(15)N signatures of nitrogen at the base of the food chain will provide a useful tool in the assessment of anthropogenic nutrient inputs.

A conserved family of elav-like genes in vertebrates.

A large family of genes encodes proteins with RNA recognition motifs that are presumed to bind RNA and to function in posttranscriptional regulation. Neural-specific members of this family include elav, a gene required for correct differentiation and maintenance of neurons in Drosophila melanogaster, and a related gene, HuD, which is expressed in human neuronal cells. I have identified genes related to elav and HuD in Xenopus laevis, zebrafish, and mouse that define a family of four closely related vertebrate elav-like genes (elrA, elrB, elrC, and elrD) in fish, frogs, and mammals. In addition to protein sequence conservation, a segment of the 3'-untranslated sequence of elrD is also conserved, implying a functional role in elrD expression. In adult frogs, elrC and elrD are exclusively expressed in the brain, whereas elrB is expressed in brain, testis, and ovary. During Xenopus development, elrC and elrD RNAs are detected by late gastrula and late neurula stages, respectively, whereas a nervous system-specific elrB RNA species is expressed by early tadpole stage. Additional elrB transcripts are detected in the ovary and early embryo, demonstrating a maternal supply of mRNA and possibly of protein. These expression patterns suggest a role for different elav-like genes in early development and neuronal differentiation. Surprisingly, elrA is expressed in all adult tissues tested and at all times during development. Thus, the widely expressed elrA is expected to have a related function in all cells.

Invasion, Proliferation and Control of Invasive Aquatic Plants in Colorado State Parks

Nonnative aquatic species are invasive worldwide. These species adversely affect natural aquatic ecosystems in a variety of ways and can negatively affect agriculture, recreation and industry. This study addresses identification and control of aquatic plant species of concern in Colorado State Parks. Seventeen species identified as potential threats to the parks and safe, effective chemical control methodologies were determined for each species. A matrix was developed to include the plants, appropriate chemical controls and the type of aquatic habitat where chemical use would be safe and effective. The matrix and recommendations for its use will be provided to the Colorado Division of Parks and Outdoor Recreation to develop a management plan under Section 1204 of the National Invasive Species Act.

Policy Development at a Local Level to Mitigate Depositing Endocrine Disruptors into Aquatic Ecosystems

Endocrine disruptors are suspected to cause disruption to organisms in aquatic environments. Intersex fish and skewed populations of females outnumbering males have been found where effluents from municipal wastewater treatment plants enter into receiving waters. The science needed to substantiate a link of these suspected pollutants as the cause of problems to human health or the environmental is in its infancy. Empirical research was used to identify suspected endocrine disruptors, their sources, and the difficulties involved in regulating these emerging contaminants. This project examined entities that are addressing endocrine disruption and provides cost-effective recommendations for municipalities to develop policies to mitigate the amount of endocrine disruptors entering into receiving waters and limiting the effects caused by endocrine disruption.

Developing a Citizen Volunteer Lake Monitoring Program for the Flathead Basin in Northwestern Montana for the early Detection and Prevention of the Introduction of Zebra Mussels and other Aquatic Invasive Species (AIS)

Preventing the introduction of aquatic invasive species (AIS) like zebra and quagga mussels in the U.S. is a high priority. This Capstone demonstrates zebra and quagga mussels are of concern as aquatic invasive species and a volunteer monitoring and intervention program is an effective means for early detection of AIS. This Capstone developed an AIS citizen volunteer lake monitoring program consistent with other programs concerned about AIS prevention and early detection. This Capstone concludes implementing such a voluntary program will help reduce the spread of zebra and quagga mussels and will provide early detection information to appropriate agencies empowered with response actions if species are found.

Post-glacial fossil vertebrates from east-central Illinois / by Edwin C. Galbreath.

v.6:no.20(1938)

Ordovician vertebrates from Western United States / Robert H. Denison --

v.16:no.6(1967)

New and little known genera and species of vertebrates from the Lower Permian of Oklahoma / [by] Everett C. Olson -- [Patricia M. Williams, editor]

v.18:no.3(1970)

Clearing and staining skeletons of small vertebrates / by D. Dwight Davis -- and U. R. Gore ; Wilfred H. Osgood --, editor.

no.4(1936)

Early devonian vertebrates from the Keoydart formation of Nova Scotia.

v.37:no.17(1955)