The development of luminal digestion of lactoferrin was evaluated in vitro by incubating 125I-labeled lactoferrin with fluid flushed from the stomach and small intestine of 12-day-old suckling and 31-day-old weanling rats, followed by measurement of radioactivity in trichloroacetic acid-soluble material. Gastric hydrolysis of lactoferrin at pH 3.2 in the weanling was 20-fold greater than that in the suckling. In the small intestine at neutral pH, luminal degradation of lactoferrin was minimal in the suckling but increased significantly after weaning, with maximal degradative capacity demonstrable in the midjejunum. Sephadex G-75 chromatography of intestinal acid-soluble breakdown products revealed two peaks of radioactivity, each comprising 40-45% of the total product; analysis of intestinal acid-precipitable products by polyacrylamide gel electrophoresis yielded several discrete lower molecular weight species. Food deprivation for 12 h/100 g body wt decreased lactoferrin degradation in the weanling jejunum and midjejunum. Our findings suggest that lactoferrin digestion may vary with respect to postnatal age of the organism, segment of the gastrointestinal tract, and dietary state. In the young animal, lactoferrin degradation is minimal, and consequently its potential for biological function may be high.
The enhancement of freshwater fisheries through stocking and introductions has always been fraught with controversy (Cowx, 1994, 1999, 2002a), with the principal concerns being predation, competition, loss of genetic integrity of the indigenous stocks and disruption of ecosystem functioning (Cowx, 1999). Although actions are taken to ensure stocked fishes are in good condition at the time of introduction (Cowx, 1994), little attention is given to issues such as the appropriate stocking density relative to the carrying capacity of the receiving water body or the availability of suitable habitat conditions. Yet these are fundamental issues if the stocked fishes are to prosper in the new environment and require addressing if stocking programmes are to be successful, socially acceptable, and return the maximum benefits for investment. Therefore, for any stocking enhancement programme to be successful it is essential that the receiving water body offers the appropriate habitat and environmental conditions for the stocked fishes to thrive and not just survive. One particular situation that has come under increased scrutiny in recent years is the stocking of barbel Barbus barbus (L.) into still waters to enhance recreational catch-and-release fisheries (North, 2001). Barbel is a rheophilic
Abstract In recent years, policy‐makers have sought the development of appropriate tools to prevent and manage introductions of invasive species. However, these tools are not well suited for introductions of non‐target species that are unknowingly released alongside intentionally‐introduced species. The most compelling example of such invasion is arguably the topmouth gudgeon Pseudorasbora parva, a small cyprinid species originating from East Asia. A combination of sociological, economical and biological factors has fuelled their rapid invasion since the 1960s; 32 countries (from Central Asia to North Africa) have been invaded in less than 50 years. Based on a combination of monitoring surveys (2535 populations sampled) and literature reviews, this paper aims to quantify and characterise important invasion parameters, such as pathways of introduction, time between introduction and detection, lag phase and plasticity of life history traits. Every decade, five new countries have reported P. parva introduction, mainly resulting from the movement of Chinese carps for fish farming. The mean detection period after first introduction was 4 years, a duration insufficient to prevent their pan‐continental invasion. High phenotypic plasticity in fitness related traits such as growth, early maturity, fecundity, reproductive behaviour and the ability to cope with novel pathogens has predisposed P. parva to being a strong invader. The Pseudorasbora parva invasion has provided quantitative data for the development of 1) early warning systems across different spatial scales; 2) rapid eradication programmes prior to natural spread in open systems and 3) sound risk assessments with emphasis on plasticity of life history traits.
Biological invasions and human migrations have increased globally due to socio-economic drivers and environmental factors that have enhanced cultural, economic, and geographic connectivity. Both processes involve the movement, establishment, and spread of species, yet unfold within fundamentally different philosophical, social and biological contexts. Hence, studying biological invasions (invasion science) and human migration (migration studies) presents complex parallels that are potentially fruitful to explore. Here, we examined nuanced parallels and differences between these two phenomena, integrating historical, socio-political, and ethical perspectives. Our review underscores the need for context-specific approaches in policymaking and governance to address effectively the challenges and opportunities of human migration and harm from biological invasions. We suggest that approaches to studying the drivers of biological invasions and human migration provide an excellent opportunity for transdisciplinary research; one that acknowledges the complexities and potential insights from both fields of study. Ultimately, integrating natural and social sciences offers a promising avenue for enriching the understanding of invasion biology and migration dynamics while pursuing just, equitable, and sustainable solutions. However, while human migration is a clear driver of biological invasions, drawing on principles from biological invasions to understand past and current human migration risks oversimplification and the potential for harmful generalisations that disregard the intrinsic rights and cultural dynamics of human migrations. By doing so, we provide insights and frameworks to support the development of context-specific policies that respect human dignity, foster cultural diversity, and address migration challenges in ways that promote global cooperation and justice. This interdisciplinary approach highlights the potential for transdisciplinary research that acknowledges complexities in both fields, ultimately enriching our understanding of invasion biology and migration dynamics while pursuing equitable and sustainable solutions.
Assessments of the trophic consequences of invasive fishes are important for quantifying their ecological impacts on native species more generally. A small-bodied cyprinid fish native to continental Europe and introduced in the 1970s to the U.K, the sunbleak Leuciscus delineatus, has been shown previously to establish closer social associations with native species of similar size than do native species amongst themselves. To assess the potential detrimental trophic consequences of native species associations with L. delineatus, a field-based experiment was undertaken in summer 2015 in six outdoor, artificial ponds containing three native cyprinid species (rudd Scardinius erthrophthalamus, gudgeon Gobio gobio, tench Tinca tinca). Three ponds were controls (no L. delineatus) and three were treatments (L. delineatus present). The results of stable isotope analysis (SIA) of fish tissue samples provided strong evidence that the isotopic niches of both native benthic fishes were reduced in the presence of L. delineatus, although there were no significant effects on the trophic position, body size or condition of two of the three native fish species. Introduced L. delineatus maintained a core isotopic niche that was distinct from the two native benthic fishes, with no overlap detected between native and non-native fishes when including 40% and 95% of the data. These results indicate that the response of the native fishes to the introduction of L. delineatus was niche constriction via trophic specialisation, with this response sufficient to maintain their growth rates and condition. This result is similar to studies on a range of small-bodied invasive fishes, suggesting the trophic impacts of these invaders are relatively consistent across species and systems.
Invasion risk assessments are reliant on ecological data that assist the predictions of whether an introduced species will adapt to novel conditions. Data from the native range of potential invaders can thus assist these assessments. Here, the growth and reproductive characteristics of the Western tubenose goby Proterorhinus semilunaris , a Ponto-Caspian gobiid, were assessed in three natural lakes in their native range, as there are few extant data on these traits. Across the three lakes, the gobies were found in varying abundances. Sex ratios varied, with females significantly outnumbering males in only one lake, with equal sex ratios in the other lakes. The fish always showed a positive allometric growth, but had high variability in their somatic growth rates and relative body conditions between the lakes. Scale ageing revealed all populations comprised of individuals to four years old, with one lake having individuals to 5 years old. Reproductive characteristics, including size at maturity, gonado-somatic index and fecundity, did not differ significantly between the lakes. These data suggest that plasticity in aspects of their life history traits provides P. semilunaris with considerable adaptive capacity following their introduction into novel conditions.
Abstract Background Clostridioides difficile is a common healthcare associated pathogen in U.S. hospitals, incurring billions of dollars in treatment costs each year. Microbiome analysis of C. difficile infected (CDI) patients have revealed alterations of the gut microbiota. It has been speculated that select members of this altered microbiota may influence C. difficile pathogenesis. C. difficile is known to reside in the intestinal mucus layer, but at present the interactions between C. difficile and other mucus-associated bacteria are poorly defined. To address these gaps in knowledge, we have focused on an entirely human-centered approach, employing human-derived MUC2, fecal bioreactors and patient samples. We hypothesized that select mucus-associated bacteria would promote C. difficile colonization and biofilm formation. Methods & Results To create a model of the human intestinal mucus layer and gut microbiota, we developed a bioreactor system with human MUC2-coated coverslips. Bioreactors were inoculated with healthy human feces, treated with clindamycin and infected with C. difficile to mimic CDI. C. difficile was found to colonize and form biofilms on MUC2-coated coverslips and 16S rRNA sequencing revealed a unique biofilm profile with substantial co-colonization with Fusobacterium. Consistent with our bioreactor data, publicly available datasets and patient stool samples revealed that a subset of patients with C. difficile infection harbored high levels of F. nucleatum OTUs. We also isolated microbes from adult patients and pediatric IBD patient stool who were positive for C. difficile and F. nucleatum and identified co-localization between these strains. RNAseq data revealed significant changes in C. difficile chemotaxis and surface adhesion genes following exposure to F. nucleatum metabolites. C. difficile was found to co-aggregate with F. nucleatum; an effect that was inhibited by blocking the Fusobacterial adhesin RadD and C. difficile flagella. Moreover, a ΔradD mutant of F. nucleatum lost the ability to aggregate with C. difficile. Conversely, removal of flagella from C. difficile significantly reduced the interaction between WT F. nucleatum and C. difficile. Addition of F. nucleatum also enhanced C. difficile biofilm formation, increasing the levels extracellular polysaccharide. Conclusions Collectively, these data demonstrate the unique role of mucus-associated bacteria such as F. nucleatum in facilitating colonization of the mucus layer by pathogenic C. difficile.
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