14 research outputs found

    Transient photoreception in the hindbrain is permissive to the life history transition of hatching in Atlantic halibut

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    In nonmammalian vertebrates, photoreception takes place in the deep brain already early in development, but knowledge is lacking about the functions of these nonvisual photoreceptive systems. Prior to hatching, Atlantic halibut has a transient bilateral cluster of photoreceptive cells in the hindbrain. The cluster is imbedded in a neuronal network projecting to the narrow belt of hatching glands in the yolk sac. In halibut, hatching is inhibited in light and activated by transfer to darkness and c-fos analysis during hatching shows that the hindbrain cluster and hatching glands have neural activation. Unexpectedly, the hindbrain cluster expresses dual photopigments, vertebrate ancient opsin and melanopsin. Evolutionarily, these opsins are believed to belong to different classes of photopigments found in rhabdomeric and ciliary photoreceptors. The concept that an organism develops transient light sensitivity to target critical aspects of life history transitions as hatching provides a fascinating landscape to investigate the timing of other biological events.acceptedVersio

    Genomic Signatures of Within-Generation Selection in Coho Salmon (Oncorhynchus kisutch) under Enriched Hatchery-Rearing Practices and in the Wild

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    Salmonids occupy central roles in the ecological and human communities in which they occur. As such, many salmonid populations are heavily managed for conservation and to support their harvest. This often involves hatcheries, which typically use captured mature adults to produce fertilized eggs which are reared to the smolt life-history stage, with resultant smolts released into the wild. Despite a history of over 150 years of hatchery use, fundamental questions remain about the ecological and evolutionary impacts of hatcheries on released fish and on the wild populations released fish interact with. Chief among these questions is the role and impact of selection in hatchery fish compared to wild fish and if domesticating processes are inevitable. In this thesis, I present a detailed investigation of the population genomics of an integrated hatchery-wild coho salmon (Oncorhynchus kisutch) population subjected to long-term experimental rearing under conventional hatchery environments, and under enriched hatchery environments designed to mimic aspects of the wild environment in efforts to mitigate potential effects of hatchery rearing. Specifically, I investigated (1) if spatial genetic structuring occurs among wild fish in this system, (2) if selection is detectable for survival-at-sea and for survival across the lifecycle within a single generation, and (3) if such selection depends on the rearing environment fish experience in the hatchery. I additionally reviewed what is known about gene expression under domestication in salmonids. I found no evidence for spatial genetic structuring among wild fish, indicating the typical strategy of restricted sampling of wild fish for inclusion in the hatchery broodstock should not drive differentiation between hatchery and wild fish. I also found evidence for within-generation selection for both survival-at-sea and survival across the lifecycle, and most importantly, that these signatures of selection differed between hatchery fish reared under different environments. Notably, signatures of selection for fish reared under enriched environments were not more similar to those observed in wild fish, compared to conventionally reared fish, indicating work remains in designing hatchery environments that mimic those aspects of the wild environment required to produce wild-like fish, and with implications for captive rearing programs more broadly

    The biogeochemistry of metal cycling

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    The results of the Planetary Biology and Microbial Ecology's summer 1987 program are summarized. The purpose of the interdisciplinary PBME program is to integrate, via lectures and laboratory work, the contributions of university and NASA scientists and student interns. The 1987 program examined various aspects of the biogeochemistry of metal cycling, and included such areas as limnology, metal chemistry, metal geochemistry, microbial ecology, and interactions with metals. A particular area of focus was the use of remote sensing in the study of biogeochemistry. Abstracts and bibliographies of the lectures and reports of the laboratory projects are presented

    The Anthropocene Hypothesis

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    American Literature and Science

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    Literature and science are two disciplines are two disciplines often thought to be unrelated, if not actually antagonistic. But Robert J. Scholnick points out that these areas of learning, up through the beginning of the nineteenth century, “were understood as parts of a unitary endeavor.By mid-century they had diverged, but literature and science have continued to interact, conflict, and illuminate each other. In this innovative work, twelve leaders in this emerging interdisciplinary field explore the long engagement of American writers with science and uncover science’s conflicting meanings as a central dimension of the nation’s conception of itself. Reaching back to the Puritan poet-minister-physician Edward Taylor, who wrote at the beginning of the scientific revolution, and forward to Thomas Pynchon, novelist of the cybernetic age, this collection of original essays contains essential work on major writers, including Franklin, Jefferson, Poe, Emerson, Thoreau, Twain, Hart Crane, Dos Passos, and Charles Olson. Through its exploration of the ways that American writers have found in science and technology a vital imaginative stimulus, even while resisting their destructive applications, this book points towards a reconciliation and integration within culture. An innovative look at a neglected dimension of our literary tradition, American Literature and Science stands as both a definition of the field and an invitation to others to continue and extend new modes of inquiry. A thoughtful collection that reveals how the concept of ‘science’ has evolved from Franklin to cyberpunk, and how it has transformed American literary form and expression. —American Literature Innovative. . . . The first systematic examination of this neglected dimension of the American literary tradition. —American Renaissance Literary Reporthttps://uknowledge.uky.edu/upk_english_language_and_literature_north_america/1013/thumbnail.jp

    Bowdoin Orient v.132, no.1-24 (2002-2003)

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    https://digitalcommons.bowdoin.edu/bowdoinorient-2000s/1003/thumbnail.jp

    Bowdoin Orient v.126, no.1-23 (1995-1996)

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    https://digitalcommons.bowdoin.edu/bowdoinorient-1990s/1007/thumbnail.jp
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