Selection due to multi-generational domestication and genetically distinct origins raises concerns about potential fitness consequences of hybridization between farmed and wild Atlantic salmon. In ...Newfoundland (NF), Canada, the aquaculture industry uses the North American (NA) Saint John River strain, though site-specific permission has been granted to farm a European origin (EO) strain. We used complementary experiments to investigate differences in (1) dominance status and (2) growth and survival in allopatry (NF wild fish) versus sympatry (NF wild fish with NA/EO farmed individuals and related F1 hybrids) in contrasting tank and semi-natural stream environments. NA farmed salmon were more dominant than NF wild individuals, with hybrids being intermediate in expression and not differing from wild fish. EO farmed salmon also tended to dominate NF wild individuals, but not significantly. Competition with farmed fish and hybrids did not affect the growth of wild fish in sympatry versus allopatry in the tank environment. However, that was not the case in one instance in the stream environment where wild fish in sympatry with NA farmed fish and hybrids outgrew those in allopatry. Within sympatric treatments, both EO and NA farmed salmon outgrew wild individuals in the tank environment, but not always in the stream environment (exception: NA farmed). Hybrids tended to display intermediate growth performance relative to farmed and wild fish in both environments. Survival did not differ among cross types in either environment. These findings suggest that irrespective of distinct origins, both EO and NA farmed salmon displayed greater dominance and growth than NF wild salmon in the tank environment. However, in the stream environment, competition imposed by NA farmed fish and related hybrids on wild fish appeared less than that imposed by the EO strain and related hybrids, as evident in growth performance. Findings thus provide valuable insight into the effects of hybridization and, consequently, fitness-related trait differences among divergent EO and NA farmed, NF wild, and F1 hybrid populations of importance for the conservation and management of Atlantic salmon.
The authors investigated the extent to which touch, vision, and audition mediate the processing of statistical regularities within sequential input. Few researchers have conducted rigorous ...comparisons across sensory modalities; in particular, the sense of touch has been virtually ignored. The current data reveal not only commonalities but also modality constraints affecting statistical learning across the senses. To be specific, the authors found that the auditory modality displayed a quantitative learning advantage compared with vision and touch. In addition, they discovered qualitative learning biases among the senses: Primarily, audition afforded better learning for the final part of input sequences. These findings are discussed in terms of whether statistical learning is likely to consist of a single, unitary mechanism or multiple, modality-constrained ones.
Nuclear inclusion X (NIX), the etiological agent of bacterial gill disease in Pacific razor clams
Siliqua patula
, was associated with host mortality events in coastal Washington State, USA, during ...the mid-1980s. Ongoing observations of truncated razor clam size distributions in Kalaloch Beach, Washington, raised concerns that NIX continues to impact populations. We conducted a series of spatial and longitudinal NIX surveillances, examined archived razor clam gill tissue, and used population estimates from stock assessments to test whether (1) the prevalence and intensity of NIX infections is higher at Kalaloch Beach relative to nearby beaches, (2) infected gill tissue has features consistent with historical descriptions of NIX-associated histopathology, and (3) annual clam survival is inversely related to NIX infection prevalence and intensity. NIX prevalence exceeded 85% at all sampled locations, and infection intensity was the highest at Kalaloch Beach by 0.9-2.6 orders of magnitude. Kalaloch Beach clams revealed histopathology consistent with previous NIX epidemics, including enlarged and/or rupturing branchial epithelial cells, branchial necrosis, and high hemocyte densities. Estimated annual survival was 22% at Kalaloch Beach, and ranged between 57 and 99% at other study sites. NIX infection intensity (via quantitative PCR) was not significantly correlated with annual survival; however, annual survival was lowest at Kalaloch Beach, where infection intensities were highest, suggesting that clams can tolerate infections up to a lethal threshold. Collectively these data support the hypothesis that high NIX intensities are associated with host mortality. NIX-associated mortality appears to be more pronounced at Kalaloch Beach relative to other Washington beaches.
Preliminary evidence suggests that Chinook salmon Oncorhynchus tshawytscha from the Yukon River may be more susceptible to Ichthyophonus sp. infections than Chinook from stocks further south. To ...investigate this hypothesis in a controlled environment, we experimentally challenged juvenile Chinook from the Yukon River and from the Salish Sea with Ichthyophonus sp. and evaluated mortality, infection prevalence and infection load over time. We found that juvenile Chinook salmon from a Yukon River stock were more susceptible to ichthyophoniasis than were those from a Salish Sea stock. After feeding with tissues from infected Pacific herring Clupea pallasii, Chinook salmon from both stocks became infected. The infection was persistent and progressive in Yukon River stock fish, where infections sometimes progressed to mortality, and histological examinations revealed parasite dissemination and proliferation throughout the host tissues. In Salish Sea-origin fish, however, infections were largely transient; host mortalities were rare, and parasite stages were largely cleared from most tissues after 3-4 wk. Susceptibility differences were evidenced by greater cumulative mortality, infection prevalence, parasite density, proportion of fish demonstrating a cellular response, and intensity of the cellular response among fish from the Yukon River stock. These observed differences between Chinook salmon stocks were consistent when parasite exposures occurred in both freshwater and seawater. These results support the hypothesis that a longer-standing host-pathogen relationship, resulting in decreased disease susceptibility, exists among Salish Sea Chinook salmon than among Yukon River conspecifics.
Sequential learning in non-human primates Conway, Christopher M.; Christiansen, Morten H.
Trends in Cognitive Sciences,
12/2001, Letnik:
5, Številka:
12
Book Review, Journal Article
Recenzirano
Sequential learning plays a role in a variety of common tasks, such as human language processing, animal communication, and the learning of action sequences. In this article, we investigate ...sequential learning in non-human primates from a comparative perspective, focusing on three areas: the learning of arbitrary, fixed sequences; statistical learning; and the learning of hierarchical structure. Although primates exhibit many similarities to humans in their performance on sequence learning tasks, there are also important differences. Crucially, non-human primates appear to be limited in their ability to learn and represent the hierarchical structure of sequences. We consider the evolutionary implications of these differences and suggest that limitations in sequential learning may help explain why non-human primates lack human-like language.
Non-lethal pathogen testing can be a useful tool for fish disease research and management. Our research objectives were to determine if (1) fin clips, gill snips, surface mucus scrapings, blood ...draws, or kidney biopsies could be obtained non-lethally from 3 to 15 g Chinook salmon Oncorhynchus tshawytscha, (2) non-lethal samples could accurately discriminate between fish exposed to the bacterial kidney disease agent Renibacterium salmoninarum and non-exposed fish, and (3) non-lethal samples could serve as proxies for lethal kidney samples to assess infection intensity. Blood draws and kidney biopsies caused ≥5% post-sampling mortality (Objective 1) and may be appropriate only for larger fish, but the other sample types were non-lethal. Sampling was performed over 21 wk following R. salmoninarum immersion challenge of fish from 2 stocks (Objectives 2 and 3), and nested PCR (nPCR) and real-time quantitative PCR (qPCR) results from candidate non-lethal samples were compared with kidney tissue analysis by nPCR, qPCR, bacteriological culture, enzyme-linked immunosorbent assay (ELISA), fluorescent antibody test (FAT) and histopathology/immunohistochemistry. R. salmoninarum was detected by PCR in >50% of fin, gill, and mucus samples from challenged fish. Mucus qPCR was the only non-lethal assay exhibiting both diagnostic sensitivity and specificity estimates>90% for distinguishing between R. salmoninarum-exposed and non-exposed fish and was the best candidate for use as an alternative to lethal kidney sample testing. Mucus qPCR R. salmoninarum quantity estimates reflected changes in kidney bacterial load estimates, as evidenced by significant positive correlations with kidney R. salmoninarum infection intensity scores at all sample times and in both fish stocks, and were not significantly impacted by environmental R. salmoninarum concentrations.
Research problem: The purpose of the study is to understand how affective reactions to color impact learning attitudes and outcomes in a computer-mediated learning environment. Research question: How ...do color differences change affective processes and outcomes in computer-mediated communication? Literature review: Several previous studies exploring particular characteristics and learning in computer-mediated environments influenced the review of the literature. The literature on color psychology indicates that color preferences and affective reactions to color can influence behaviors and attitudes. The literature on goal achievement motivation posits that affective dispositions influence goal orientation, motivation, and individual outcomes. The literature on affect infers that affective reactions are responses to events, and these reactions influence attitudes and behaviors. The current study draws on these prior studies to examine affective reaction to color and learning outcomes in a computer-mediated learning environment. Methodology: We conducted a quasiexperimental study with 79 participants, who listened to a visual presentation lecture with either blue or yellow background and then completed a survey on their affective reactions, learning attitudes, and outcomes. Results and discussion: The results of our study indicate that color is not neutral and may influence learning attitudes and outcomes and, hence, the color of computer technology interface design can influence learning outcomes. Practitioners and academics must take people's affective reactions to color into account in designs and studies of visual information presentations. The sample size and the focus on two color hues (yellow and blue) may have some limitations on the conclusions and generalizability of this study. Future studies should examine more color hues and color saturation to further our understanding of affective reactions to colors and consequent impact on attitudes and behavioral outcomes.
A highly efficacious DNA vaccine against a fish rhabdovirus, infectious hematopoietic necrosis virus (IHNV), was used in a systematic study to analyze vaccine tissue distribution, persistence, ...expression patterns, and histopathologic effects. Vaccine plasmid pIHNw-G, containing the gene for the viral glycoprotein, was detected immediately after intramuscular injection in all tissues analyzed, including blood, but at later time points was found primarily in muscle tissue, where it persisted to 90 days. Glycoprotein expression was detected in muscle, kidney, and thymus tissues, with levels peaking at 14 days and becoming undetectable by 28 days. Histologic examination revealed no vaccine-specific pathologic changes at the standard effective dose of 0.1 mug DNA per fish, but at a high dose of 50 mug an increased inflammatory response was evident. Transient damage associated with needle injection was localized in muscle tissue, but by 90 days after vaccination no damage was detected in any tissue, indicating the vaccine to be safe and well tolerated.
The purpose of this inquiry was to examine the beginning music teacher mentor practices in 13 school districts in mid-Michigan. Data included beginning teacher interviews, teacher journals, ...focus-group meetings, mentor interviews, administrator interviews, and the principal investigator's log. Profiles of the teachers show a lack of consistency in the types of mentor programs in the schools and varying degrees of teacher satisfaction with the programs. The lack of consistency is discussed in relation to the type of school, the teaching responsibility and classroom setting, the type of mentor assigned, and the degree to which that mentor was paid or trained. Teacher perceptions of the value of the program are discussed in relation to the degree and type of contact with the assigned mentor. The content of mentor interactions included administrative duties, classroom management, parent interaction, building and district policies, and personal issues. The need for music mentors is discussed, and the article concludes with general suggestions for mentor practices, including early identification of mentor, scheduling so mentors can observe, and opportunities for mentors and mentees to get to know each other.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, OILJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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