Iron (Fe) is an essential micronutrient for diazotrophs, which are abundant in the Western Tropical South Pacific Ocean (WTSP). Their success depends on the numerous trace metals, particularly Fe, released from shallow hydrothermal vents along the Tonga Arc. This study aimed to explore the spatio‐temporal impact of hydrothermal fluids on particulate trace metal concentrations and biological activity. To identify the composition of sinking particles across a wide area of the WTSP, we deployed sediment traps at various depths, both close and further west of the Tonga Arc. Seafloor sediments were cored at these deployment sites, including at a remote location in the South Pacific Gyre. The sinking particles were composed of a large amount of biological material (up to 88 mg d⁻¹), indicative of the high productivity of the region. A significant portion of this material (∼21 ± 12 wt.%) was lithogenic of hydrothermal origin, as revealed through Al‐Fe‐Mn tracing. The sinking material showed similar patterns between lithogenic and biogenic fractions, indicating that hydrothermal input within the photic layer triggered surface production. A hydrothermal fingerprint was suggested in the sediments due to the high sedimentation rates (>47 cm kyr⁻¹) and the presence of large, heterogeneous, metal‐rich particles. The presence of nearby active deep hydrothermal sources was suspected near the Lau Ridge due to the large particle size (1–976 μm) and the significant excess of Fe and Mn (2–20 wt.%). Overall, this study revealed that hydrothermal sources have a significant influence on the biogeochemical signature of particles in the region.
The distribution of the recent Lymnaeidae across continents and zoogeographical regions of the world is reviewed, with a brief characteristic of the geographical distribution of each extant lymnaeid genus. The quantitative estimates of the similarity between the lymnaeid faunas of different continents and the largest zoogeographical regions are provided and discussed. It is shown that the highest taxonomic level of endemism in the family is observed in the Nearctic region, and the overall faunal similarity is highest among the Palaearctic and Oriental region, whereas the Australian fauna is the most peculiar. A special section of the article is devoted to a review of the invasive lymnaeid species and the possible consequences of their invasions to the non-native areas.
The article provides a brief introduction to the Lymnaeidae and contains short reviews of taxonomy, the fossil record, morphology, biogeography, and ecology of these snails, with an emphasis on the extant representatives of the family.
Digeneans (Platyhelminthes, Trematoda) are considered as a very ancient and as the most diversified group of internal metazoan parasites of animals. They can have important detrimental effects on human and animal health. They also affect populations dynamics of their hosts, are able to shape the structure of communities, and can act as determinants of ecosystems structure and functioning. Whereas life-cycles are diversified, the fundamental life-cycle of digeneans is characterized by a mollusc as the first intermediate host, where an important asexual multiplication occurs and by a vertebrate as definitive host. The interactions between digeneans and molluscs are complex; they start with the infection of the mollusc by the miracidial larval stage, which implies molecular mechanisms of attraction, recognition, and attachment. Once the penetration successful, an intimate association starts between the mollusc and the digenean, where the mollusc displays an intense immune response and, in turn, the digenean counter-attacks by different mechanisms. All these complex interactions can lead to high reciprocal specializations which can lead to host–parasite specificity. After its installation, the miracidium converts into a sporocyst which develops and starts an intense asexual multiplication, highly detrimental for the molluscan fitness. At the end of several cycles of asexual reproduction, the last larval stages, the cercariae, are emitted and will serve to infect the following host. Taking into account the complexity of mollusc–digenean interactions, their sensitivity to environmental perturbations and their importance in ecological and epidemiological risks, such interactions have to be particularly scrutinized. In this chapter, we review such host–parasite interactions with emphasis on the Lymnaeidae.
This chapter aims to familiarize the readers with terminology and basic concepts applied to conchological and anatomical characters that have been widely used for the identification of lymnaeid snails. The main diagnostic traits of the lymnaeid shell and soft body anatomy are reviewed and illustrated.
The family Lymnaeidae is globally recognized for its role in the transmission of fasciolosis. This chapter thoroughly reviews the species of lymnaeid snails that have a proven or suspected role in the transmission of the liver flukes Fasciola hepatica and Fasciola gigantica. An outline of the differential roles of each major clade is presented with relation to the ecology of the species that helps to understand the epidemiological risks at different geographic levels. The chapter is accompanied by a detailed list of recorded prevalences either natural or experimental for 31 species of Lymnaeidae reviewed by country.
Herein, general aspects of the relationship between lymnaeid snails and their parasites are reviewed from a mechanistic point of view. It includes an outlook to encounter filters whilst emphasizing on compatibility filters driven by the different components of the internal defense system within Lymnaeidae, and to the immunobiological interactions that determined the recognition and elimination of the pathogen upon contact, or the establishment of the dynamic equilibrium characteristic of a successful infection. The negative effects caused by parasitism on the physiology and life history traits of the lymnaeid hosts are briefly reviewed, as well as the role of ecological factors on modifying encounter and compatibility filters and the ultimate infection outcome. Finally, insights into the significance of building up knowledge on the biology of host–parasite interaction will be discussed to introduce the opportunities and challenges that lies ahead concerning the family Lymnaeidae and their most significant pathogens. Most of the published works on the subject deals with Lymnaeidae–trematode interaction and consequently, this represents the main topic reviewed in this chapter.
The history of the lymnaeid research, from the mid-sixteenth century to the present, is briefly outlined, with a special emphasis on the development of the systematics of this family and the studies of parasitological significance of the pond snails. An index to the lymnaeid literature published during the last 120 years, which includes references to the most important publications, is also provided.
The objective of this chapter is to review the different methods for field control of host snails involved in the transmission of fasciolosis. Environmental measures such as drainage of swampy soils or cutting of vegetation in watercourses can reduce the number of snails. Synthetic molluscicides are being used less and less because of their cost, toxicity, and contamination they cause in the environment. Conversely, research on plant extracts is being developed because many of them are natural molluscicides that are less toxic and more environmentally friendly. In the nature, several groups of vertebrates and invertebrates predate lymnaeids and a control technique of Galba truncatula has been developed in central France using predation by the terrestrial snail Zonitoides nitidus. Biological control can be performed using animal species which compete with lymnaeids for food. Pathogens such as parasites and other infectious agents can also be used. Finally, an integrated liver fluke control strategy for the control of liver fluke, associating deworming of the definitive hosts and control of host snails, is analysed with a review of results provided by this type of control.
This study focuses on metal/polymer nanocomposite thin films made by atmospheric pressure Plasma-Enhanced Chemical Vapor Deposition. The aerosol of isopropanol-dissolved tetrachloroauric acid (HAuCl4:3H2O gold salt) is injected in a dielectric barrier discharge to synthesize plasmonic nanocomposite thin films. Argon is used as carrier gas with or without 133 ppm addition of ammonia (NH3) to respectively get or not a Penning mixture. Results show that NH3 largely influences the salt reduction and thin film properties. According to the aerosol characterization, the size distribution at the plasma entrance supports that isopropanol mainly evaporates before injection in the plasma. The salt initially dissolved in each droplet precipitates during evaporation before injection as solid nanoparticles of about 30 nm diameter with eventual traces of solvent. Then, the nanocomposite thins film are studied. Optical properties, as plasmonic resonance, are characterized by UV–visible absorption spectroscopy. The chemical composition is analyzed using X-ray photoelectron spectroscopy and Raman spectroscopy, complemented by X-ray diffraction analysis as well as chemical mapping obtained by Energy dispersive spectroscopy coupled to scanning electron microscopy (SEM) operating in Scanning Transmission Electron Microscopy mode. Additionally, the morphology of the deposits is investigated by atomic force microscopy and SEM, highlighting the influence of NH3 gas on the film nature and therefore its role in the overall deposition process. Finally, optical emission spectroscopy of the plasma gives clue to better understand the effect of NH3. The overall results show that the salt nanoparticles are reduced in the plasma phase leading to non-aggregated metal Au NPs embedded in a carbon-based matrix formed by isopropanol polymerization. The presence of NH3 in the plasma unambiguously decreases the salt reduction and affects the thin film properties, consequently changing their plasmonic response related to the size, concentration, and composition of the embedded NPs.
The reproductive systems of natural populations can greatly impact their genetic diversity by preventing or encouraging inbreeding. It is therefore crucial to have a comprehensive understanding of the mating system to evaluate a population’s ability to maintain genetic diversity over time. In this study, we examine the mating system of an endangered population of green sea turtles in Tetiaroa, French Polynesia. We determine if different mating behaviours serve as strategies to avoid inbreeding. We genotyped 107 nesting females and 1483 hatchlings from 549 nests and used 23 microsatellite markers to reconstruct the genotypes of the fathers. We assessed the level of inbreeding and relatedness of the parent pairs and explored the correlation between relatedness and fitness parameters in the offspring. We determined the mating behaviours of both males and females and investigated if specific behaviours were linked to different levels of relatedness. Our results showed that 27 fathers and 31 mothers were responsible for the genotypes of 445 hatchlings from 105 nests. Global Fis was significant, and levels of relatedness were higher than expected through random mating, indicating inbreeding and non-random partner selection. However, we did not find any mating behaviours that were associated with lower relatedness levels than the general population, suggesting that they are not part of an inbreeding avoidance strategy. Ultimately, this study illuminates the reproductive system of green turtles and shows that this population is susceptible to inbreeding. Additionally, our research demonstrates the effectiveness of parentage analysis in understanding the reproductive behaviour of elusive species.
Rearing density directly impacts fish welfare, which, in turn, affects productivity in aquaculture. Previous studies have indicated that high-density rearing during sexual development in fish can induce stress, resulting in a tendency towards male-biased sex ratios in the populations. In recent years, research has defined the relevance of the interactions between the environment and epigenetics playing a key role in the final phenotype. However, the underlying epigenetic mechanisms of individuals exposed to confinement remain elucidated. By using zebrafish (Danio rerio), the DNA methylation promotor region and the gene expression patterns of six genes, namely dnmt1, cyp19a1a, dmrt1, cyp11c1, hsd17b1, and hsd11b2, involved in the DNA maintenance methylation, reproduction, and stress were assessed. Zebrafish larvae were subjected to two high-density conditions (9 and 66 fish/L) during two periods of overlapping sex differentiation of this species (7 to 18 and 18 to 45 days post-fertilization, dpf). Results showed a significant masculinization in the populations of fish subjected to high densities from 18 to 45 dpf. In adulthood, the dnmt1 gene was differentially hypomethylated in ovaries and its expression was significantly downregulated in the testes of fish exposed to high-density. Further, the cyp19a1a gene showed downregulation of gene expression in the ovaries of fish subjected to elevated density, as previously observed in other studies. We proposed dnmt1 as a potential testicular epimarker and the expression of ovarian cyp19a1a as a potential biomarker for predicting stress originated from high densities during the early stages of development. These findings highlight the importance of rearing densities by long-lasting effects in adulthood conveying cautions for stocking protocols in fish hatcheries.
The orientational dynamics of supercooled glycerol is probed using molecular dynamics simulations for temperatures ranging from 323 K to 253 K, through correlation functions of first and second ranks of Legendre polynomials, pertaining respectively to dielectric spectroscopy (DS) and depolarized dynamic light scattering (DDLS). The self, cross, and total correlation functions are compared with relevant experimental data. The computations reveal the low sensitivity of DDLS to cross-correlations, in agreement with what is found in experimental work, and strengthen the idea of directly comparing DS and DDLS data to evaluate the effect of cross-correlations in polar liquids. The analysis of the net static cross-correlations and their spatial decomposition shows that, although cross-correlations extend over nanometric distances, their net magnitude originates, in the case of glycerol, from the first shell of neighbouring molecules. Accessing the angular dependence of the static correlation allows us to get a microscopic understanding of why the rank-1 correlation function is more sensitive to cross-correlation than its rank-2 counterpart.
Recently, we reported programmed Cas9 mediated insertion of a reporter gene into a gene safe harbor site, GSH1, of Schistosoma mansoni via homology-directed repair (HDR) using overlapping guide RNAs. Here, we report efficient and precise CRISPR/Cas12a-mediated homology directed insertion (knockin, KI) of a 5’ C6-PEG10-modified double-stranded transgene bearing microhomology arms, 50 nt in length, at GSH1. At the outset, we undertook bioinformatic and computational analysis following by experimental verification of the regulatory activity of endogenous schistosome ubiquitin (SmUbi) promoter and terminator, to drive strong reporter gene expression. Green fluorescent protein activity driven by SmUbi followed electroporation-mediated transfection of schistosome eggs. HDR induced by RNA-guided CRISPR/Cas12a, which releases overhanging DNA strands of 18-24, delivered more efficient KI than CRISPR/Cas9. In this non-model pathogen, programmed KI facilitated precise chromosomal integration of the reporter-gene with at GSH1. The approach advances schistosome transgenesis field and may also advance functional genomics and transfection methods in related parasitic and non-parasitic helminths, which hitherto lack these tools.
Horizontal transfer (HT) refers to the exchange of genetic material between divergent species by mechanisms other than reproduction. In recent years, several studies have demonstrated HTs in eukaryotes, particularly in the context of parasitic relationships and in model species. However, very little is known about HT in natural ecosystems, especially those involving non-parasitic wild species, and the nature of the ecological relationships that promote these HTs. In this work, we conducted a pilot study investigating HTs by sequencing the genomes of 17 wild non-model species from a natural ecosystem, the Massane forest, located in southern France. To this end, we developed a new computational pipeline called INTERCHANGE that is able to characterize HTs at the whole genome level without prior annotation and directly in the raw sequencing reads. Using this pipeline, we identified 12 HT events, half of which occurred between lianas and trees. We found that mainly low copy number LTR-retrotransposons from the Copia superfamily were transferred between these wild plant species, especially those of the Ivana and Ale lineages. This study revealed a possible new route for HTs between non-parasitic plants and provides new insights into the genomic characteristics of horizontally transferred DNA in plant genomes.
Ecosystem recovery from human‐induced disturbances, whether through natural processes or restoration, is occurring worldwide. Yet, recovery dynamics, and their implications for broader ecosystem management, remain unclear. We explored recovery dynamics using coral reefs as a case study. We tracked the fate of 809 individual coral recruits that settled after a severe bleaching event at Lizard Island, Great Barrier Reef. Recruited Acropora corals, first detected in 2020, grew to coral cover levels that were equivalent to global average coral cover within just 2 years. Furthermore, we found that just 11.5 Acropora recruits per square meter were sufficient to reach this cover within 2 years. However, wave exposure, growth form and colony density had a marked effect on recovery rates. Our results underscore the importance of considering natural recovery in management and restoration and highlight how lessons learnt from reef recovery can inform our understanding of recovery dynamics in high‐diversity climate‐disturbed ecosystems.
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