Hybridization creates novel gene combinations that may generate important evolutionary novelty, but may also reduce existing adaptation by interrupting inherent biological processes, such as ...genotype-environment interactions. Hybridization often causes substantial change in patterns of gene expression, which, in turn, may cause phenotypic change. Rainbow trout (Oncorhynchus mykiss) and cutthroat trout (O. clarkii) produce viable hybrids in the wild, and introgressive hybridization with introduced rainbow trout is a major conservation concern for native cutthroat trout. The two species differ in body shape, which is likely an evolutionary adaptation to their native environments, and their hybrids tend to show intermediate morphology. The characterization of gene expression patterns may provide insights on the genetic basis of hybrid and parental morphologies, as well as on the ecological performance of hybrids in the wild. Here, we evaluated the expression of eight growth-related genes (MSTN-1a, MSTN-1b, MyoD1a, MyoD1b, MRF-4, IGF-1, IGF-2, and CAST-L) and the relationship of these genes with growth traits (length, weight, and condition factor) in six line crosses: both parental species, both reciprocal F1 hybrids, and both first-generation backcrosses (F1 x rainbow trout and F1 x cutthroat trout). Four of these genes were differentially expressed among rainbow, cutthroat, and their hybrids. Transcript abundance was significantly correlated with growth traits across the parent species, but not across hybrids. Our findings suggest that rainbow and cutthroat trout exhibit differences in muscle growth regulation, that transcriptional networks may be modified by hybridization, and that hybridization disrupts intrinsic relationships between gene expression and growth patterns that may be functionally important for phenotypic adaptations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Knowledge of the timing of major life history events in aquatic species is important for informing conservation and resource management planning. Accordingly, surveys of environmental DNA (eDNA) have ...been performed to determine the efficacy of eDNA for providing information on life history events, primarily focusing on the timing of events associated with spawning, and these studies have proved successful. However, spawning represents only one part of the life history, and therefore, information on eDNA shedding during other life history stages is needed to fill gaps in knowledge. Here, we explored eDNA shedding during early life history (from fertilized eggs until near yolk sac absorption) in Chinook Salmon (Oncorhynchus tshawytscha) at three biomasses in a laboratory environment. We found that fertilized eggs shed little eDNA prior to hatching. Hatching coincided with a spike in eDNA, and we observed a significant and positive relationship between eDNA concentration and the number of hatched eggs. The concentration of eDNA shed by larvae after hatching was not consistent across post‐hatch sampling days, suggesting developmental and behavioral changes associated with larval ontogeny may affect eDNA shedding rate. These results indicate that eDNA data may be used to identify hatch timing and verify successful reproduction in oviparous aquatic fishes. The application of eDNA to early life history broadens the capacity of eDNA‐based methods for assessing population status and trends.
The power of eDNA‐based methods as a resource management tool can be improved with greater understanding of how changes in eDNA concentrations relate to important life history events, behavior, and ecology. Published studies have demonstrated the efficacy of eDNA as tool for monitoring life history events associated with reproduction, and here, we focus on eDNA shedding during early life history in Chinook Salmon across a continuum of ontogenetic stages covering pre‐hatch, hatch, and post‐hatch prior to the onset of exogenous feeding, a period spanning 79 days in this study. Our results suggest that eDNA shedding during early life history could be exploited and used as an indicator of ontogenetic transition from one developmental stage to another, broadening the capacity of eDNA‐based methods for assessing population status and trends.
Lampreys have a worldwide distribution, are functionally important to ecological communities and serve significant roles in many cultures. In Pacific coast drainages of North America, lamprey ...populations have suffered large declines. However, lamprey population status and trends within many areas of this region are unknown and such information is needed for advancing conservation goals. We developed two quantitative PCR-based, aquatic environmental DNA (eDNA) assays for detection of Pacific Lamprey (
) and
spp, using locked nucleic acids (LNAs) in the probe design. We used these assays to characterize the spatial distribution of lamprey in 18 watersheds of Puget Sound, Washington, by collecting water samples in spring and fall. Pacific Lamprey and
spp were each detected in 14 watersheds and co-occurred in 10 watersheds. Lamprey eDNA detection rates were much higher in spring compared to fall. Specifically, the Pacific Lamprey eDNA detection rate was 3.5 times higher in spring and the
spp eDNA detection rate was 1.5 times higher in spring even though larval lamprey are present in streams year-round. This significant finding highlights the importance of seasonality on eDNA detection. Higher stream discharge in the fall likely contributed to reduced eDNA detection rates, although seasonal life history events may have also contributed. These eDNA assays differentiate Pacific Lamprey and
spp across much of their range along the west coast of North America. Sequence analysis indicates the Pacific Lamprey assay also targets other
spp and indicates the
spp assay may have limited or no capability of detecting
in some locations south of the Columbia River Basin. Nevertheless, these assays will serve as a valuable tool for resource managers and have direct application to lamprey conservation efforts, such as mapping species distributions, occupancy modeling, and monitoring translocations and reintroductions.
Environmental DNA (eDNA) has emerged as a potentially powerful tool for use in conservation and resource management, including for tracking the recolonization dynamics of fish populations. We used ...eDNA to assess the effectiveness of dam removal to restore fish passage on the Elwha River in Washington State (USA). Using a suite of 11 species‐specific eDNA polymerase chain reaction (PCR) assays, we showed that most targeted anadromous species (five Pacific Salmon species and Pacific Lamprey) were able to pass upstream of both former dam sites. Multiscale occupancy modeling showed that the timing and spatial extent of recolonization differed among species during the four years of post‐dam removal monitoring. More abundant species like Chinook Salmon and Coho Salmon migrated farther into the upper portions of the watershed than less abundant species like Pink Salmon and Chum Salmon. Sampling also allowed assessment of potamodromous fish species. Bull Trout and Rainbow Trout, ubiquitous species in the watershed, were detected at all sampling locations. Environmental DNA from Brook Trout, a non‐native species isolated between the dams prior to dam removal, was detected downstream of Elwha dam but rarely upstream of the Glines Canyon Dam suggested that the species has not expanded its range appreciably in the watershed following dam removal. We found that eDNA was an effective tool to assess the response of fish populations to large‐scale dam removal on the Elwha River.
We collected eDNA data from the Elwha River, home to the world’s largest dam removal project. Our goal was to track the emergence of spatial patterns and species reassembly following dam removal. In total, we have data for 11 different fish taxa, sampled at 25 sites ranging across 56 river kilometers in a wilderness river for 4 years following dam removal. We show that eDNA can effectively be used to determine whether fish have recolonized past former dams and in some cases determine the spatial extent of that recolonization.
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.
Surveys of environmental DNA (eDNA) have become an important and multifaceted tool for monitoring and identifying distributions and occupancy of aquatic species. This tool is attractive because it is ...powerful, easy to apply, and provides an alternative to traditional field survey methods. However, validating eDNA survey methods against traditional field survey methods is warranted prior to their application. We used eDNA and electrofishing to survey 10 sites in 3 tributaries of the Chehalis River, Washington, to infer distribution and occupancy of Entosphenus tridentatus and Lampetra spp. Both methods produced similar detection rates for E. tridentatus, and Lampetra spp. were detected at slightly greater frequency with eDNA in the Black River and Skookumchuck River. Within each of the three tributaries, eDNA concentration was negatively related to sample distance from the Chehalis River mainstem for E. tridentatus but not for Lampetra spp., which indicates E. tridentatus and Lampetra spp. may be distributed differently within tributaries. Application of lamprey eDNA data to a multiscale occupancy model indicated high probability of detecting eDNA in water samples and quantitative PCR (qPCR) assays. Broad distribution and high detection of E. tridentatus and Lampetra spp. suggest robust populations inhabit the Chehalis River basin. Our findings suggest eDNA surveys may be comparable to electrofishing for informing lamprey occupancy and distributions. Such sampling is efficient and cost‐effective and we anticipate that eDNA surveys will become a valuable tool in addressing key research and monitoring needs for conservation and restoration of lampreys in general.
US Geological Survey, Biological Resources Discipline, Western Fisheries Research Center, 6505 N.E. 65th Street, Seattle, WA 98115, USA.
Renibacterium salmoninarum is an important salmonid pathogen ...that is difficult to culture. We developed and assessed a real-time, quantitative, polymerase chain reaction (qPCR) assay for the detection and enumeration of R. salmoninarum. The qPCR is based on TaqMan technology and amplifies a 69-base pair (bp) region of the gene encoding the major soluble antigen (MSA) of R. salmoninarum. The qPCR assay consistently detected as few as 5 R. salmoninarum cells per reaction in kidney tissue. The specificity of the qPCR was confirmed by testing the DNA extracts from a panel of microorganisms that were either common fish pathogens or reported to cause false-positive reactions in the enzyme-linked immunosorbent assay (ELISA). Kidney samples from 38 juvenile Chinook salmon (Oncorhynchus tshawytscha) in a naturally infected population were examined by real-time qPCR, a nested PCR, and ELISA, and prevalences of R. salmoninarum detected were 71, 66, and 71%, respectively. The qPCR should be a valuable tool for evaluating the R. salmoninarum infection status of salmonids.
Brazilian elodea (
Egeria densa
) is an invasive freshwater plant that demonstrates widespread ecological impacts in freshwater ecosystems and causes substantial economic damage. Here, we developed ...an environmental DNA assay for detection of
E. densa
to provide resource managers with a tool for early detection, identification, and monitoring of invasive populations.
We evaluated genetic variation in ability of Chinook salmon (Oncorhynchus tshawytscha) to resist two bacterial pathogens: Renibacterium salmoninarum, the agent of bacterial kidney disease (BKD), and ...Listonella anguillarum, an agent of vibriosis. After measuring R. salmoninarum antigen in 499 adults by enzyme-linked immunosorbent assay (ELISA), we mated each of 12 males with high or low antigen levels to two females with low to moderate levels and exposed subsets of their progeny to each pathogen separately. We found no correlation between R. salmoninarum antigen level in parents and survival of their progeny following pathogen exposure. We estimated high heritability for resistance to R. salmoninarum (survival h
2
= 0.890 ± 0.256 (mean ± standard error)) independent of parental antigen level, but low heritability for resistance to L. anguillarum (h
2
= 0.128 ± 0.078). The genetic correlation between these survivals (r
A
= -0.204 ± 0.309) was near zero. The genetic and phenotypic correlations between survival and antigen levels among surviving progeny exposed to R. salmoninarum were both negative (r
A
= -0.716 ± 0.140; r
P
= -0.378 ± 0.041), indicating that variation in antigen level is linked to survival. These results suggest that selective culling of female broodstock with high antigen titers, which is effective in controlling BKD in salmon hatcheries, will not affect resistance of their progeny.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Prevention of Hypoglycemia During Exercise in Children With Type 1 Diabetes by Suspending Basal Insulin
the Diabetes Research in Children Network (DirecNet) Study Group *
Address correspondence and ...reprint requests to Eva Tsalikian, MD, c/o DirecNet Coordinating Center, Jaeb Center for Health
Research, 15310 Amberly Dr., Suite 350, Tampa, FL 33647. E-mail: direcnet{at}jaeb.org
Abstract
OBJECTIVE —Strategies for preventing hypoglycemia during exercise in children with type 1 diabetes have not been well studied. The Diabetes
Research in Children Network (DirecNet) Study Group conducted a study to determine whether stopping basal insulin could reduce
the frequency of hypoglycemia occurring during exercise.
RESEARCH DESIGN AND METHODS —Using a randomized crossover design, 49 children 8–17 years of age with type 1 diabetes on insulin pump therapy were studied
during structured exercise sessions on 2 days. On day 1, basal insulin was stopped during exercise, and on day 2 it was continued.
Each exercise session, performed from ∼4:00–5:00 p.m. , consisted of four 15-min treadmill cycles at a target heart rate of 140 bpm (interspersed with three 5-min rest breaks over
75 min), followed by a 45-min observation period. Frequently sampled glucose concentrations (measured in the DirecNet Central
Laboratory) were measured before, during, and after the exercise.
RESULTS —Hypoglycemia (≤70 mg/dl) during exercise occurred less frequently when the basal insulin was discontinued than when it was
continued (16 vs. 43%; P = 0.003). Hyperglycemia (increase from baseline of ≥20% to ≥200 mg/dl) 45 min after the completion of exercise was more frequent
without basal insulin (27 vs. 4%; P = 0.002). There were no cases of abnormal blood ketone levels.
CONCLUSIONS —Discontinuing basal insulin during exercise is an effective strategy for reducing hypoglycemia in children with type 1 diabetes,
but the risk of hyperglycemia is increased.
DirecNet, Diabetes Research in Children Network
Footnotes
*
↵ * A complete list of DirecNet Study Group members can be found in the appendix .
↵ A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore
be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Accepted July 13, 2006.
Received March 3, 2006.
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