The environmental context of inducible HSP70 expression in Eastern Brook Trout.
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ABSTRACT:
SUBMITTER: Nguyen BV
PROVIDER: S-EPMC8111384 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The highly conserved heat shock protein 70 (HSP70) contributes to survival at a cellular level and greatly enhances stress tolerance in many organisms. In this study, we isolate and characterize Cshsp702, which encodes an inducible form of HSP70 in the rice stem borer, Chilo suppressalis. Cshsp702 does not contain introns; the translational product is comprised of 629 amino acids with an isoelectric point of 5.69. Real-time quantitative PCR revealed that Cshsp702 was expressed at maximal levels in hemocytes and was minimally expressed in the midgut. Expression of Cshsp702 in response to a range of temperatures (-11 to 43 °C) indicated significant induction by extreme cold and hot temperatures, with maximum expression after 2 h at 42 °C. The induction of Cshsp702 in response to the endoparasite Cotesia chilonis was also studied; interestingly, Cshsp702 expression in C. suppressalis was significantly induced at 24 h and 5 days, which correspond to predicted times of C. chilonis feeding and growth, respectively. The potential induction of Cshsp702 as an inflammatory response due to parasitic stress is discussed. In conclusion, Cshsp702 is induced in response to both environmental and biotic stress and plays an important role in the physiological adaptation of C. suppressalis.
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Project description:Brook trout (Salvelinus fontinalis) spawn in fall and overwintering egg development can benefit from stable, relatively warm temperatures in groundwater-seepage zones. However, eggs are also sensitive to dissolved oxygen concentration, which may be reduced in discharging groundwater (i.e., seepage). We investigated a 2 km reach of the coastal Quashnet River in Cape Cod, Massachusetts, USA, to relate preferred fish spawning habitats to geology, geomorphology, and discharging groundwater geochemistry. Thermal reconnaissance methods were used to locate zones of rapid groundwater discharge, which were predominantly found along the central channel of a wider stream valley section. Pore-water chemistry and temporal vertical groundwater flux were measured at a subset of these zones during field campaigns over several seasons. Seepage zones in open-valley sub-reaches generally showed suboxic conditions and higher dissolved solutes compared to the underlying glacial outwash aquifer. These discharge zones were cross-referenced with preferred brook trout redds and evaluated during 10 years of observation, all of which were associated with discrete alcove features in steep cutbanks, where stream meander bends intersect the glacial valley walls. Seepage in these repeat spawning zones was generally stronger and more variable than in open-valley sites, with higher dissolved oxygen and reduced solute concentrations. The combined evidence indicates that regional groundwater discharge along the broader valley bottom is predominantly suboxic due to the influence of near-stream organic deposits; trout show no obvious preference for these zones when spawning. However, the meander bends that cut into sandy deposits near the valley walls generate strong oxic seepage zones that are utilized routinely for redd construction and the overwintering of trout eggs. Stable water isotopic data support the conclusion that repeat spawning zones are located directly on preferential discharges of more localized groundwater. In similar coastal systems with extensive valley peat deposits, the specific use of groundwater-discharge points by brook trout may be limited to morphologies such as cutbanks, where groundwater flow paths do not encounter substantial buried organic material and remain oxygen-rich.
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Project description:Hybridization can profoundly affect the genomic composition and phenotypes of closely related species, and provides an opportunity to identify mechanisms that maintain reproductive isolation between species. Recent evidence suggests that hybridization outcomes within a species pair can vary across locations. However, we still do not know how variable outcomes of hybridization are across geographic replicates, and what mechanisms drive that variation. In this study, we described hybridization outcomes across 27 locations in the North Fork Shoshone River basin (Wyoming, USA) where native Yellowstone cutthroat trout and introduced rainbow trout co-occur. We used genomic data and hierarchical Bayesian models to precisely identify ancestry of hybrid individuals. Hybridization outcomes varied across locations. In some locations, only rainbow trout and advanced backcrossed hybrids towards rainbow trout were present, while trout in other locations had a broader range of ancestry, including both parental species and first-generation hybrids. Later-generation intermediate hybrids were rare relative to backcrossed hybrids and rainbow trout individuals. Using an individual-based simulation, we found that outcomes of hybridization in the North Fork Shoshone River basin deviate substantially from what we would expect under null expectations of random mating and no selection against hybrids. Since this deviation implies that some mechanisms of reproductive isolation function to maintain parental taxa and a diversity of hybrid types, we then modelled hybridization outcomes as a function of environmental variables and stocking history that are likely to affect prezygotic barriers to hybridization. Variables associated with history of fish stocking were the strongest predictors of hybridization outcomes, followed by environmental variables that might affect overlap in spawning time and location.
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Project description:Fragmentation can strongly influence population persistence and expression of life-history strategies in spatially-structured populations. In this study, we directly estimated size-specific dispersal, growth, and survival of stream-dwelling brook trout in a stream network with connected and naturally-isolated tributaries. We used multiple-generation, individual-based data to develop and parameterize a size-class and location-based population projection model, allowing us to test effects of fragmentation on population dynamics at local (i.e., subpopulation) and system-wide (i.e., metapopulation) scales, and to identify demographic rates which influence the persistence of isolated and fragmented populations. In the naturally-isolated tributary, persistence was associated with higher early juvenile survival ( approximately 45% greater), shorter generation time (one-half) and strong selection against large body size compared to the open system, resulting in a stage-distribution skewed towards younger, smaller fish. Simulating barriers to upstream migration into two currently-connected tributary populations caused rapid (2-6 generations) local extinction. These local extinctions in turn increased the likelihood of system-wide extinction, as tributaries could no longer function as population sources. Extinction could be prevented in the open system if sufficient immigrants from downstream areas were available, but the influx of individuals necessary to counteract fragmentation effects was high (7-46% of the total population annually). In the absence of sufficient immigration, a demographic change (higher early survival characteristic of the isolated tributary) was also sufficient to rescue the population from fragmentation, suggesting that the observed differences in size distributions between the naturally-isolated and open system may reflect an evolutionary response to isolation. Combined with strong genetic divergence between the isolated tributary and open system, these results suggest that local adaptation can 'rescue' isolated populations, particularly in one-dimensional stream networks where both natural and anthropogenically-mediated isolation is common. However, whether rescue will occur before extinction depends critically on the race between adaptation and reduced survival in response to fragmentation.
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Project description:Sustainable management of exploited populations benefits from integrating demographic and genetic considerations into assessments, as both play a role in determining harvest yields and population persistence. This is especially important in populations subject to size-selective harvest, because size selective harvesting has the potential to result in significant demographic, life-history, and genetic changes. We investigated harvest-induced changes in the effective number of breeders ( N^b ) for introduced brook trout populations (Salvelinus fontinalis) in alpine lakes from western Canada. Three populations were subject to 3 years of size-selective harvesting, while three control populations experienced no harvest. The N^c decreased consistently across all harvested populations (on average 60.8%) but fluctuated in control populations. There were no consistent changes in N^b between control or harvest populations, but one harvest population experienced a decrease in N^b of 63.2%. The N^b / N^c ratio increased consistently across harvest lakes; however we found no evidence of genetic compensation (where variance in reproductive success decreases at lower abundance) based on changes in family evenness ( FE^ ) and the number of full-sibling families ( N^fam ). We found no relationship between FE^ and N^c or between N^fam / N^c and FE^ . We posit that change in N^b was buffered by constraints on breeding habitat prior to harvest, such that the same number of breeding sites were occupied before and after harvest. These results suggest that effective size in harvested populations may be resilient to considerable changes in Nc in the short-term, but it is still important to monitor exploited populations to assess the risk of inbreeding and ensure their long-term survival.
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Project description:The environment an organism experiences during early development can impact its physiology and survival later in life. The objective of this study was to determine if temperatures experienced at embryonic life stages of brook trout (Salvelinus fontinalis) affected mass and routine metabolic rate (RMR) of a subsequent life stage (free-swimming fry). As part of this, we assessed the contributions and importance of hierarchical levels of biological organization [ancestral type (native vs. hatchery-introgressed), population, and family] to variability in mass and RMR of fry. As embryos and alevin, individuals were reared at either natural environmental (5°C) or elevated (9°C) temperatures and then acclimated to either matched or mismatched temperature treatments once yolk sacs were resorbed. Mass differences among fry were strongly influenced by population of origin as well as initial rearing and final acclimation temperatures. Variation in mass-adjusted RMR of fry was also strongly accounted for by source population, acclimation temperature, and individual mass. A significant interaction between population RMR and final acclimation temperature indicated that not all brook trout populations responded the same way to temperature changes. In contrast to expectations, the highest ancestry category (native vs. introgressed) did not significantly influence mass or mass-adjusted RMR.
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Project description:Nonparasitic Lethenteronreissneri (Dybowski) is redescribed based on four syntypes (two adults and two ammocoetes) from the Onon and Ingoda rivers, Russia, and 15 topotypic specimens (seven metamorphosing ammocoetes and eight ammocoetes) from the Onon River system, Russia and Mongolia. Posterial teeth were not mentioned in the original description, but Berg (1931) stated that they were sometimes absent, which he later (Berg 1948) changed to usually absent, based on material (some of which we have re-identified as parasitic Lethenteroncamtschaticum) from far outside of the type locality. The latter view has been widely accepted by subsequent authors. Unfortunately, the poor condition of the two adult syntypes did not permit verification of this character. However, a row of posterials was clearly visible in six of the seven topotypic metamorphosing ammocoetes and indicates their usual presence in the species. The first full description of the ammocoetes, including pigmentation, is provided. The present study restricts the distribution of Lethenteronreissneri to the Shilka and Songhua river systems within the Amur River basin, until a more geographically comprehensive study is undertaken. Additionally, in this study, feeding versus non-feeding at the adult stage, are considered to be valid taxonomic characters at the species level.
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Project description:A fundamental issue in the management and conservation of biodiversity is how to define a population. Spatially contiguous fish occupying a stream network have often been considered to represent a single, homogenous population. However, they may also represent multiple discrete populations, a single population with genetic isolation-by-distance, or a metapopulation. We used microsatellite DNA and a large-scale mark-recapture study to assess population structure in a spatially contiguous sample of Brook Trout (Salvelinus fontinalis), a species of conservation concern. We found evidence for limited genetic exchange across small spatial scales and in the absence of barriers to physical movement. Mark-recapture and stationary passive integrated transponder antenna records demonstrated that fish from two tributaries very seldom moved into the opposite tributary, but movements between the tributaries and mainstem were more common. Using Bayesian genetic clustering, we identified two genetic groups that exhibited significantly different growth rates over three years of study, yet survival rates were very similar. Our study highlights the importance of considering the possibility of multiple genetically distinct populations occurring within spatially contiguous habitats, and suggests the existence of a cryptic metapopulation: a spatially continuous distribution of organisms exhibiting metapopulation-like behaviors.
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Project description:Twenty-nine bacterial isolates representing eight genera from the gastrointestinal tracts of feral brook trout Salvelinus fontinalis (Mitchell) demonstrated multiple maximal antibiotic resistances and concomitant broad-spectrum mercury (Hg) resistance. Equivalent viable plate counts on tryptic soy agar supplemented with either 0 or 25 μM HgCl(2) verified the ubiquity of mercury resistance in this microbial environment. Mercury levels in lake water samples measured 1.5 ng L(-1); mercury concentrations in fish filets ranged from 81.8 to 1,080 ng g(-1) and correlated with fish length. The presence of similar antibiotic and Hg resistance patterns in multiple genera of gastrointestinal microflora supports a growing body of research that multiple selective genes can be transferred horizontally in the presence of an unrelated individual selective pressure. We present data that bioaccumulation of non-point source Hg pollution could be a selective pressure to accumulate both antibiotic and Hg resistant bacteria.
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Project description:Due to increased anthropogenic pressures on many fish populations, supplementing wild populations with captive-raised individuals has become an increasingly common management practice. Stocking programs can be controversial due to uncertainty about the long-term fitness effects of genetic introgression on wild populations. In particular, introgression between hatchery and wild individuals can cause declines in wild population fitness, resiliency, and adaptive potential and contribute to local population extirpation. However, low survival and fitness of captive-raised individuals can minimize the long-term genetic consequences of stocking in wild populations, and to date the prevalence of introgression in actively stocked ecosystems has not been rigorously evaluated. We quantified the extent of introgression in 30 populations of wild brook trout (Salvelinus fontinalis) in a Pennsylvania watershed and examined the correlation between introgression and 11 environmental covariates. Genetic assignment tests were used to determine the origin (wild vs. captive-raised) for 1,742 wild-caught and 300 hatchery brook trout. To avoid assignment biases, individuals were assigned to two simulated populations that represented the average allele frequencies in wild and hatchery groups. Fish with intermediate probabilities of wild ancestry were classified as introgressed, with threshold values determined through simulation. Even with reoccurring stocking at most sites, over 93% of wild-caught individuals probabilistically assigned to wild origin, and only 5.6% of wild-caught fish assigned to introgressed. Models examining environmental drivers of introgression explained <3% of the among-population variability, and all estimated effects were highly uncertain. This was not surprising given overall low introgression observed in this study. Our results suggest that introgression of hatchery-derived genotypes can occur at low rates, even in actively stocked ecosystems and across a range of habitats. However, a cautious approach to stocking may still be warranted, as the potential effects of stocking on wild population fitness and the mechanisms limiting introgression are not known.
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