Comparison of heat-shock responses between the hydrothermal vent shrimp Rimicaris exoculata and the related coastal shrimp Palaemonetes varians

The deep-sea vent shrimp Rimicaris exoculata is believed to occur at the hot end of the hydrothermal biotope in order to provide essential elements to its epibiosis. Because it is found close to hot venting water, R. exoculata lives in a highly fluctuating environment where temperature (2–40 °C in the swarms) can exceed its critical maximal temperature (33–38.5 ± 2 °C). In order to understand how this vent shrimp copes with hyperthermia, we compared its molecular heat stress response following an acute but non-lethal heat-shock (1 h at 30 °C) with that of its monophyletic shallow-water relative, the shrimp Palaemonetes varians, known to frequently undergo prolonged exposure at temperatures up to 30 °C in its natural environment during summer. We isolated four isoforms of heat-shock proteins 70 (HSP70) in R. exoculata (2 constitutive and 2 inducible isoforms) and two isoforms in P. varians (1 constitutive and 1 inducible isoform) and quantitatively compared their magnitude of induction at mRNA level, using real-time PCR, in the case of experimentally heat-stressed shrimps, with respect to control (unstressed) animals. Here, we report the first quantification of the expression of multiple hsp70 genes following heat stress in a deep-sea vent species living at 2300 m depth. Our results show a strong increase of hsp70 inducible genes in the vent shrimp (not, vert, similar 400-fold) compared to the coastal shrimp (not, vert, similar 15-fold). We therefore propose that, the highly inducible molecular response observed in R. exoculata may contribute to the ability of this species to tolerate thermal extremes

To focus-match or not to focus-match inverse spatially offset Raman spectroscopy : a question of light penetration

Funding: The work was supported by funding from the UK Engineering and Physical Sciences Research Council (EP/P030017/1 and EP/R004854/1) and the H2020 FETOPEN project “Dynamic” (EC-GA 863203).The ability to identify the contents of a sealed container, without the need to extract a sample, is desirable in applications ranging from forensics to product quality control. One technique suited to this is inverse spatially offset Raman spectroscopy (ISORS) which illuminates a sample of interest with an annular beam of light and collects Raman scattering from the centre of the ring, thereby retrieving the chemical signature of the contents while suppressing signal from the container. Here we explore in detail the relative benefits of a recently developed variant of ISORS, called focus-matched ISORS. In this variant, the Fourier relationship between the annular beam and a tightly focused Bessel beam is exploited to focus the excitation light inside the sample and to match the focal point of excitation and collection optics to increase the signal from the contents without out compromising the suppression of the container signal. Using a flexible experimental setup which can realise both traditional and focus-matched ISORS, and Monte-Carlo simulations, we elucidate the relative advantages of the two techniques for a range of optical properties of sample and container.Publisher PDFPeer reviewe

Microbial diversity associated with the hydrothermal shrimp Rimicaris exoculata gut and occurrence of a resident microbial community

En libre-accès sur Archimer : http://archimer.ifremer.fr/doc/00000/11142/7919.pdfInternational audienceRimicaris exoculata dominates the megafauna of several Mid-Atlantic Ridge hydrothermal sites. Its gut is full of sulphides and iron-oxide particles and harbours microbial communities. Although a trophic symbiosis has been suggested, their role remains unclear. In vivo starvation experiments in pressurized vessels were performed on shrimps from Rainbow and Trans-Atlantic Geotraverse sites in order to expel the transient gut contents. Microbial communities associated with the gut of starved and reference shrimps were compared using 16S rRNA gene libraries and microscopic observations (light, transmission and scanning electron microscopy and FISH analyses). We show that the gut microbiota of shrimps from both sites included mainly Deferribacteres, Mollicutes, Epsilon- and Gammaproteobacteria. For the first time, we have observed filamentous bacteria, inserted between microvilli of gut epithelial cells. They remained after starvation periods in empty guts, suggesting the occurrence of a resident microbial community. The bacterial community composition was the same regardless of the site, except for Gammaproteobacteria retrieved only in Rainbow specimens. We observed a shift in the composition of the microbiota of long-starved specimens, from the dominance of Deferribacteres to the dominance of Gammaproteobacteria. These results reinforce the hypothesis of a symbiotic relationship between R. exoculata and its gut epibionts

Insights into metazoan evolution from Alvinella pompejana cDNAs.

International audienceBACKGROUND: Alvinella pompejana is a representative of Annelids, a key phylum for evo-devo studies that is still poorly studied at the sequence level. A. pompejana inhabits deep-sea hydrothermal vents and is currently known as one of the most thermotolerant Eukaryotes in marine environments, withstanding the largest known chemical and thermal ranges (from 5 to 105°C). This tube-dwelling worm forms dense colonies on the surface of hydrothermal chimneys and can withstand long periods of hypo/anoxia and long phases of exposure to hydrogen sulphides. A. pompejana specifically inhabits chimney walls of hydrothermal vents on the East Pacific Rise. To survive, Alvinella has developed numerous adaptations at the physiological and molecular levels, such as an increase in the thermostability of proteins and protein complexes. It represents an outstanding model organism for studying adaptation to harsh physicochemical conditions and for isolating stable macromolecules resistant to high temperatures. RESULTS: We have constructed four full length enriched cDNA libraries to investigate the biology and evolution of this intriguing animal. Analysis of more than 75,000 high quality reads led to the identification of 15,858 transcripts and 9,221 putative protein sequences. Our annotation reveals a good coverage of most animal pathways and networks with a prevalence of transcripts involved in oxidative stress resistance, detoxification, anti-bacterial defence, and heat shock protection. Alvinella proteins seem to show a slow evolutionary rate and a higher similarity with proteins from Vertebrates compared to proteins from Arthropods or Nematodes. Their composition shows enrichment in positively charged amino acids that might contribute to their thermostability. The gene content of Alvinella reveals that an important pool of genes previously considered to be specific to Deuterostomes were in fact already present in the last common ancestor of the Bilaterian animals, but have been secondarily lost in model invertebrates. This pool is enriched in glycoproteins that play a key role in intercellular communication, hormonal regulation and immunity. CONCLUSIONS: Our study starts to unravel the gene content and sequence evolution of a deep-sea annelid, revealing key features in eukaryote adaptation to extreme environmental conditions and highlighting the proximity of Annelids and Vertebrates

Identifying toxic impacts of metals potentially released during deep-sea mining - a synthesis of the challenges to quantifying risk

In January 2017, the International Seabed Authority released a discussion paper on the development of Environmental Regulations for deep-sea mining (DSM) within the Area Beyond National Jurisdiction (the "Area"). With the release of this paper, the prospect for commercial mining in the Area within the next decade has become very real. Moreover, within nations' Exclusive Economic Zones, the exploitation of deep-sea mineral ore resources could take place on very much shorter time scales and, indeed, may have already started. However, potentially toxic metal mixtures may be released at sea during different stages of the mining process and in different physical phases (dissolved or particulate). As toxicants, metals can disrupt organism physiology and performance, and therefore may impact whole populations, leading to ecosystem scale effects. A challenge to the prediction of toxicity is that deep-sea ore deposits include complex mixtures of minerals, including potentially toxic metals such as copper, cadmium, zinc, and lead, as well as rare earth elements. Whereas the individual toxicity of some of these dissolved metals has been established in laboratory studies, the complex and variable mineral composition of seabed resources makes the a priori prediction of the toxic risk of DSM extremely challenging. Furthermore, although extensive data quantify the toxicity of metals in solution in shallow-water organisms, these may not be representative of the toxicity in deep-sea organisms, which may differ biochemically and physiologically and which will experience those toxicants under conditions of low temperature, high hydrostatic pressure, and potentially altered pH. In this synthesis, we present a summation of recent advances in our understanding of the potential toxic impacts of metal exposure to deep-sea meio- to megafauna at low temperature and high pressure, and consider the limitation of deriving lethal limits based on the paradigm of exposure to single metals in solution. We consider the potential for long-term and far-field impacts to key benthic invertebrates, including the very real prospect of sub-lethal impacts and behavioral perturbation of exposed species. In conclusion, we advocate the adoption of an existing practical framework for characterizing bulk resource toxicity in advance of exploitation

Etude de la réponse au stress thermique chez la crevette hydrothermale Rimicaris exoculata

La crevette hydrothermale R. exoculata forme des essaims sur les fumeurs des sites de la dorsale Médio-Atlantique. Cette espèce vit donc dans un environnement variable où les températures peuvent dépasser sa température critique maximale. L objectif de cette thèse a consisté à caractériser la réponse au stress thermique de R. exoculata afin de préciser ses conditions environnementales optimales. Plusieurs marqueurs de stress thermique ont ainsi été identifiés. L étude de l expression des gènes hsp70 a permis de mettre en évidence que R. exoculata est probablement rarement exposée à des températures supérieures à 30C pendant des périodes prolongées dans son habitat naturel. Cette hypothèse a été renforcée grâce à l utilisation du système de récolte sous pression, PERISCOP. Ces études nous ont conduits à établir un preferendum thermique de 10-25C pour cette espèce. Un comportement de thermorégulation pourrait donc être à l origine de la colonisation de cette crevette sur les fumeurs.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Assessing a species thermal tolerance through a multiparameter approach: the case study of the deep-sea hydrothermal vent shrimp Rimicaris exoculata

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