Deep-sea Organisms Research Articles

Molecular and functional characterization of short peptidoglycan recognition proteins in Vesicomyidae clam

Within cold seep environments, the Vesicomyidae clam emerges as a prevalent species, distinguished by its symbiotic relationship with microorganisms housed within its organ gill. Given the extreme conditions and the symbiotic nature of this association, investigating the host's immune genes, particularly immune recognition receptors, is essential for understanding their role in facilitating host-symbiotic interactions. Three short peptidoglycan recognition proteins (PGRPs) were identified in the clam. AmPGRP-S1, -S2, and -S3 were found to possess conserved amidase binding sites and Zn2+ binding sites. Quantitative Real-time PCR (qRT-PCR) analysis revealed differential expression patterns among the PGRPs. AmPGRP-S1 and AmPGRP-S2 exhibited elevated expression levels in the gill, while AmPGRP-S3 displayed the highest expression in the adductor muscle. Functional experiments demonstrated that recombinant AmPGRP-S1, -S2, and -S3 (rAmPGRPs) exhibited binding capabilities to both L-PGN and D-PGN (peptidoglycan). Notably, rAmPGRP-S1 and -S2 possessed Zn2+-independent amidase activity, while rAmPGRP-S3 lacked this enzymatic function. rAmPGRPs were shown to bind to five different bacterial species. Among these, rAmPGRP-S1 inhibited Escherichia coli and Bacillus subtilis, while rAmPGRP-S2 and -S3 inhibited Bacillus subtilis in the absence of Zn2+. In the presence of Zn2+, rAmPGRP-S1 and -S2 exhibited enhanced inhibitory activity against Staphylococcus aureus or Bacillus subtilis. These findings suggest that AmPGRPs may play a pivotal role in mediating the interaction between the host and endosymbiotic bacteria, functioning as PGN and microbe receptors, antibacterial effectors, and regulators of host-microbe symbiosis. These results contribute to our understanding of the adaptive mechanisms of deep-sea organisms to the challenging cold seep environments.

Comparative study of lysine acetylation in Vesicomyidae clam Archivesica marissinica and the manila clam Ruditapes philippinarum: adaptation mechanisms in cold seep environments

BackgroundThe deep-sea cold seep zone is characterized by high pressure, low temperature, darkness, and oligotrophy. Vesicomyidae clams are the dominant species within this environment, often forming symbiotic relationships with chemosynthetic microbes. Understanding the mechanisms by which Vesicomyidae clams adapt to the cold seep environment is significant. Acetylation modification of lysine is known to play a crucial role in various metabolic processes. Consequently, investigating the role of lysine acetylation in the adaptation of Vesicomyidae clams to deep-sea environments is worthwhile. So, a comparative study of lysine acetylation in cold seep clam Archivesica marissinica and shallow water shellfish Ruditapes philippinarum was conducted.ResultsA total of 539 acetylated proteins were identified with 1634 acetylation sites. Conservative motif enrichment analysis revealed that the motifs -KacR-, -KacT-, and -KacF- were the most conserved. Subsequent gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses were conducted on significantly differentially expressed acetylated proteins. The GO enrichment analysis indicated that acetylated proteins are crucial in various biological processes, including cellular response to stimulation, and other cellular processes ( p < 0.05 and false discovery rate (FDR) < 0.25). The results of KEGG enrichment analysis indicated that acetylated proteins are involved in various cellular processes, including tight junction, motor proteins, gap junction, phagosome, cGMP-PKG signaling pathways, endocytosis, glycolysis/gluconeogenesis, among others (p < 0.05 and FDR < 0.25). Notably, a high abundance of lysine acetylation was observed in the glycolysis/glycogenesis pathways, and the acetylation of glyceraldehyde 3-phosphate dehydrogenase might facilitate ATP production. Subsequent investigation into acetylation modifications associated with deep-sea adaptation revealed the specific identification of key acetylated proteins. Among these, the adaptation of cold seep clam hemoglobin and heat shock protein to high hydrostatic pressure and low temperature might involve an increase in acetylation levels. Acetylation of arginine kinase might be related to ATP production and interaction with symbiotic bacteria. Myosin heavy chain (Ama01085) has the most acetylation sites and might improve the actomyosin system stability through acetylation. Further validation is required for the acetylation modification from Vesicomyidae clams.ConclusionA novel comparative analysis was undertaken to investigate the acetylation of lysine in Vesicomyidae clams, yielding novel insights into the regulatory role of lysine acetylation in deep-sea organisms. The findings present many potential proteins for further exploration of acetylation functions in cold seep clams and other deep-sea mollusks.

Environmental DNA Metabarcoding of Cephalopod Diversity in the Tyrrhenian Deep Sea

The deep sea, the largest biome on Earth, is the least explored and understood. This lack of knowledge hampers our ability to understand and protect this important environment. In this study, water and sediment samples were collected at different depths in the central Mediterranean (224–780 m), specifically, within the Dohrn Canyon and the Palinuro Seamount, to investigate the diversity of cephalopods and establish a baseline knowledge of their distribution in these sites to preserve their habitats and estimate the impacts of human-driven environmental changes. Key taxa identified included Heteroteuthis sp., Loligo sp., and Histioteuthis sp., which were the most abundant across all sampling stations. A low overlap in species detection was observed between water and sediment samples, confirming previous findings that the typology of environmental matrices used in eDNA metabarcoding has a significant impact on the organisms detected and, therefore, the integrated use of different matrices to better represent local biodiversity is recommended. Furthermore, this study highlights the limitations posed by gaps in reference databases, particularly for deep-sea organisms, and addresses these by emphasising the need for improved multi-marker approaches and expanded reference databases to enhance the accuracy of eDNA-based biodiversity assessment.

Origin of Pressure Resistance in Deep-Sea Lactate Dehydrogenase.

High hydrostatic pressure has a dramatic effect on biochemical systems, as exposure to high pressure can result in structural perturbations ranging from dissociation of protein complexes to complete denaturation. The deep ocean presents an interesting paradox since it is teeming with life despite the high-pressure environment. This is due to evolutionary adaptations in deep-sea organisms, such as amino acid substitutions in their proteins, which aid in resisting the denaturing effects of pressure. However, the physicochemical mechanism by which these substitutions can induce pressure resistance remains unknown. Here, we use molecular dynamics simulations to study pressure-adapted lactate dehydrogenase from the deep-sea abyssal grenadier (Coryphaenoides armatus), in comparison with that of the shallow-water Atlantic cod (Gadus morhua). We examined structural, thermodynamic and volumetric contributions to pressure resistance, and report that the amino acid substitutions result in a decrease in volume of the deep-sea protein accompanied by a decrease in thermodynamic stability of the native protein. Our simulations at high pressure also suggest that differences in compressibility may be important for understanding pressure resistance in deep-sea proteins.

Cold-water octocoral interactions with microplastics under laboratory conditions

Microplastic pollution is ubiquitous in the oceans, threatening the health of marine ecosystems. The deep sea is recognized as a sink for microplastics, but there is a paucity of information on how deep-sea organisms are being affected by this stressor. Considering their vulnerability to disturbance, this information is crucial to fully understand the need for conservation actions. Here, we develop a novel methodology to provide a detailed characterisation of the behavioural responses of the cold-water octocoral Viminella flagellum to microplastic exposure under laboratory conditions. Coral fragments were individually exposed to a concentration of 1500 items/L of fluorescent green polyethylene microspheres biofouled for three weeks, for a period of 24 h, and carefully monitored for the entire exposure period using high resolution time-lapse video. After exposure, each fragment was transferred to another tank, free of microplastics, and monitored for further 24 h. The coral fragments were dissected at the end of the experimental period to assess the number of microplastics that remained in the digestive tract of each polyp. Our results showed that during this short-term exposure period, V. flagellum was ingesting microspheres, but most importantly it demonstrated the capacity of egesting all particles within 24 h. These results are especially important when quantifying microplastic contamination in cold-water corals in their natural habitat, as only recently ingested microplastics may be detected, leading to potential underestimations of their exposure. Additionally, our results indicated that microplastics adhered to the coral tissue surface could be discarded through periodic shedding of the mucus. These observations suggest that cold-water octocorals can handle microplastics as they do with other foreign particles, although the cleaning mechanisms may require significant energy expenditures.

A deep-sea isopod that consumes Sargassum sinking from the ocean's surface.

Most deep-ocean life relies on organic carbon from the surface ocean. While settling primary production rapidly attenuates in the water column, pulses of organic material can be quickly transported to depth in the form of food falls. One example of fresh material that can reach great depths across the tropical Atlantic Ocean and Caribbean Sea is the pelagic macroalgae Sargassum. However, little is known about the deep-ocean organisms able to use this food source. Here, we encountered the isopod Bathyopsurus nybelini at depths 5002-6288 m in the Puerto Rico Trench and Mid-Cayman Spreading Center using the Deep Submergence Vehicle Alvin. In most of the 32 observations, the isopods carried fronds of Sargassum. Through an integrative suite of morphological, DNA sequencing, and microbiological approaches, we show that this species is adapted to feed on Sargassum by using a specialized swimming stroke, having serrated and grinding mouthparts, and containing a gut microbiome that provides a dietary contribution through the degradation of macroalgal polysaccharides and fixing nitrogen. The isopod's physiological, morphological, and ecological adaptations demonstrate that vertical deposition of Sargassum is a direct trophic link between the surface and deep ocean and that some deep-sea organisms are poised to use this material.

Role of a novel endoplasmic reticulum-resident glycoprotein Mtc6/Ehg2 in high-pressure growth: stability of tryptophan permease Tat2 in Saccharomyces cerevisiae.

Deep-sea organisms are subjected to extreme conditions; therefore, understanding their adaptive strategies is crucial. We utilize Saccharomyces cerevisiae as a model to investigate pressure-dependent protein regulation and piezo-adaptation. Using yeast deletion library analysis, we identified 6 poorly characterized genes that are crucial for high-pressure growth, forming novel functional modules associated with cell growth. In this study, we aimed to unravel the molecular mechanisms of high-pressure adaptation in S. cerevisiae, focusing on the role of MTC6. MTC6, the gene encoding the novel glycoprotein Mtc6/Ehg2, was found to stabilize tryptophan permease Tat2, ensuring efficient tryptophan uptake and growth under high pressure at 25MPa. The loss of MTC6 led to promoted vacuolar degradation of Tat2, depending on the Rsp5-Bul1 ubiquitin ligase complex. These findings enhance our understanding of deep-sea adaptations and stress biology, with broad implications for biotechnology, environmental microbiology, and evolutionary insights across species.

Integrated transcriptomic and metabolomic approaches reveal molecular response and potential biomarkers of the deep-sea mussel Gigantidas platifrons to copper exposure

Metal pollution caused by deep-sea mining activities has potential detrimental effects on deep-sea ecosystems. However, our knowledge of how deep-sea organisms respond to this pollution is limited, given the challenges of remoteness and technology. To address this, we conducted a toxicity experiment by using deep-sea mussel Gigantidas platifrons as model animals and exposing them to different copper (Cu) concentrations (50 and 500 μg/L) for 7 days. Transcriptomics and LC-MS-based metabolomics methods were employed to characterize the profiles of transcription and metabolism in deep-sea mussels exposed to Cu. Transcriptomic results suggested that Cu toxicity significantly affected the immune response, apoptosis, and signaling processes in G. platifrons. Metabolomic results demonstrated that Cu exposure disrupted its carbohydrate metabolism, anaerobic metabolism and amino acid metabolism. By integrating both sets of results, transcriptomic and metabolomic, we find that Cu exposure significantly disrupts the metabolic pathway of protein digestion and absorption in G. platifrons. Furthermore, several key genes (e.g., heat shock protein 70 and baculoviral IAP repeat-containing protein 2/3) and metabolites (e.g., alanine and succinate) were identified as potential molecular biomarkers for deep-sea mussel’s responses to Cu toxicity. This study contributes novel insight for assessing the potential effects of deep-sea mining activities on deep-sea organisms.

At-sea application of the comet assay to a deep-sea fish

Given the go ahead, deep-sea mining operations are likely to continue for decades on a substantial spatial scale and the resulting sediment plumes combined, are likely to extend beyond the licenced mining areas, and could lead to the chronic exposure of deep-sea organisms to a mixture of metals, even mobile species, such as fish, that could conceivably display avoidance behaviour. The metal concentrations, often substantially below lethal doses, mean that individual mortality is too blunt a measure to allow assessment of “serious harm”. Commonly used cellular biomarkers of exposure in ecotoxicology include DNA damage using the Comet assay. True deep-sea ecotoxicological studies with fish are rare and to our knowledge, there are no published data or method optimizations for deep-sea fish. Coryphaenoides ssp. were collected during SMARTEX expedition 1 (Feb/Mar, 2023) to the Clarion Clipperton Zone (CCZ) in the Eastern Pacific Ocean using a baited trap deployed between 4580–4,732m depth for 24–48 h. Blood and gill tissue were removed and processed for the Comet assay. In order to reduce artefactual DNA damage from cryopreservation observed previously, two sets of samples were prepared: a cryopreservative (10% DMSO) was added to one set of samples and stored at −80 °C; the second set was used to perform a Comet assay within hours of collection. A custom-built gimble table enabled horizontal electrophoresis at sea after which Comet assay slides were dried and stored at room temperature until further analysis. The Comet assay was also assessed in freshly sampled and frozen rainbow trout cells as a proxy control in order to evaluate potential artefacts from the collection and sampling procedure of the deep-sea fish. The blood samples processed at sea had a significantly reduced level of DNA damage compared to the frozen samples. There was no significant difference between the fresh deep-sea and rainbow trout samples. However, the freshly prepared gill samples in Coryphaenoides ssp. showed substantial artefacts, possibly as a consequence of barotrauma. These results represent the first effort at establishing baseline DNA damage data for deep-sea fish, an essential component in understating and quantifying the impact of deep-sea mining.

Data Analysis in Deep-Sea Mineral and Organism Interplay: A Review

The deep sea, a realm characterized by extreme environmental conditions and remarkable biodiversity, has become a focal point for both scientific exploration and industrial exploitation. This comprehensive review aims to elucidate the data analysis techniques that are instrumental in studying the complex relationship between deep-sea mineral resources and the organisms that inhabit these extreme environments. The paper begins by outlining the types of deep-sea mineral resources and their distribution, followed by an overview of the methods and technologies used for exploration and extraction. It then delves into the diversity and classification of deep-sea organisms, their unique survival mechanisms, and their ecological roles. The core of the review focuses on data analysis techniques, covering traditional methods, advancements in machine learning and AI, and the inherent challenges and limitations in analyzing intricate deep-sea data. The paper concludes by discussing the direct and indirect impacts of mineral extraction on deep-sea ecosystems, supported by case studies and potential long-term effects on biodiversity and ecosystem health.

Consumer isoscapes reveal heterogeneous food webs in deep-sea submarine canyons and adjacent slopes

The deep sea is the largest biome on earth, but one of the least studied despite its critical role in global carbon cycling and climate buffering. Deep-sea organisms largely rely on particulate organic matter from the surface ocean for energy – these organisms in turn play critical roles in energy transport, transformation, storage, and sequestration of carbon. Within the deep sea, submarine canyons are amongst the most complex and dynamic environments in our oceans, where varied morphology, powerful currents, and variable nutrient conditions influence the distribution of species and transport of organic material throughout the water column and the seafloor. Significant habitat heterogeneity provides ideal substrates for cold-water corals, making submarine canyons of interest to conservation and management. However, how these and other topographic features in the deep ocean influence energy flow and trophic pathways is poorly known. Thus, submarine canyons serve as model systems to track variability in organic material flux and consequential utilization and assimilation by the benthos. In this study, we used an extensive stable isotope dataset to examine food-web structure in Baltimore and Norfolk submarine canyons and compared them to their adjacent slopes located along the U.S. Atlantic margin. Linear models were used to construct geospatially-explicit consumer isoscapes that predicted variation in carbon and nitrogen isotopes across the canyon-slope seascape, providing a predictive map from which to test hypotheses on the distribution and flow of energy resources, relevant to understanding whole community function. Communities were composed of isotopically diverse feeding groups with photosynthetically-derived organic carbon providing the basal food resource. Canyon communities were distinct from the slope, with canyon consumers significantly 13C-depleted, indicating a greater supply and/or utilization of fresh organic matter compared to the slope. Isoscapes for benthic and suspension feeders were distinct, possibly due to the consumption of different quality organic matter sources (fresh = suspension feeders, old = benthic feeders), each with distinct isotope composition. To our knowledge, our modeled isoscapes represent the first spatially extensive isotopic maps of deep-sea consumers, providing insights into regional-scale variation in stable carbon and nitrogen isotopes for different consumer groups. They provide a baseline for tracking climate-change induced fluctuations in the quality and availability of surface primary production and the consequential impact to benthic communities, which play critical roles in carbon cycling in our world’s oceans.

Accumulation of polychlorinated biphenyls in the ovaries of deep-sea chemosynthetic clam Phreagena okutanii

Polychlorinated biphenyls (PCBs) persistently pollute marine ecosystems even though their production has been discontinued decades ago. Deep-sea organisms have been shown to accumulate PCBs and other persistent organic compounds; however, the extent of contamination and its effects remain poorly understood. Here, we measured PCB concentrations in separated organs of non-feeding bivalve clams belonging to Phreagena, a taxon representative of deep-sea chemosynthetic ecosystems. The highest concentrations of PCBs were detected in the ovaries. We also examined surface sediments of the clam habitat and observed concentrations comparable to those in the sediments of the seas around Japan, including shallow waters. The results showed that PCBs from the environment penetrate Phreagena clams through the body surface and accumulate in the female reproductive system. This raises concerns about a potentially severe direct impact on the survival of vulnerable and highly endemic deep-sea chemosynthetic bivalves.

Effects of extreme hydrostatic pressure on the molecular structure and properties of the elastomeric material for soft robots

The successful exploration of the Mariana Trench, Earth's deepest trench, by soft robots inspired by deep-sea organisms, showcasing the potential of soft robots for extreme deep-sea exploration. However, deep-sea extreme pressure significantly alters the structure and properties of robot materials, affecting their detectability. In this study, to ensure soft robots maintain excellent performance even in such extreme environments, meticulous attention is devoted to these pressure-induced changes before designing them. The results demonstrate that applying pressure (416.67 MPa) can induce the glass transition in silicone rubber (SR) even at room temperature. Unlike the traditional realization mechanism (cooling material to its glass transition temperature (Tg)), the realization mechanism through pressurizing is reported that adjusting the Tg of target material to approach a specific temperature. Furthermore, the different transition mechanisms under the two realizations are also revealed. Based the dynamic analysis of SR under extremely low temperature and high pressure, the glass transition pressure (Pg) is proposed, and the glass transition strategy by jointly regulating temperature and pressure to construct equivalent extreme pressure environment is also investigated. This study, taking SR as the case study, holds significant importance for the future development of extreme pressure-resistant soft robots for extreme environment exploration.

An in situ digital synthesis strategy for the discovery and description of ocean life.

Revolutionary advancements in underwater imaging, robotics, and genomic sequencing have reshaped marine exploration. We present and demonstrate an interdisciplinary approach that uses emerging quantitative imaging technologies, an innovative robotic encapsulation system with in situ RNA preservation and next-generation genomic sequencing to gain comprehensive biological, biophysical, and genomic data from deep-sea organisms. The synthesis of these data provides rich morphological and genetic information for species description, surpassing traditional passive observation methods and preserved specimens, particularly for gelatinous zooplankton. Our approach enhances our ability to study delicate mid-water animals, improving research in the world's oceans.

Modulation of protein-saccharide interactions by deep-sea osmolytes under high pressure stress

Deep-sea organisms must cope with high hydrostatic pressures (HHP) up to the kbar regime to control their biomolecular processes. To alleviate the adverse effects of HHP on protein stability most organisms use high amounts of osmolytes. Little is known about the effects of these high concentrations on ligand binding. We studied the effect of the deep-sea osmolytes trimethylamine-N-oxide, glycine, and glycine betaine on the binding between lysozyme and the tri-saccharide NAG3, employing experimental and theoretical tools to reveal the combined effect of osmolytes and HHP on the conformational dynamics, hydration changes, and thermodynamics of the binding process. Due to their different chemical makeup, these cosolutes modulate the protein-sugar interaction in different ways, leading to significant changes in the binding constant and its pressure dependence. These findings suggest that deep-sea organisms may down- and up-regulate reactions in response to HHP stress by altering the concentration and type of the intracellular osmolyte.

Deep-Sea Biological Detection Method Based on Lightweight YOLOv5n.

Deep-sea biological detection is essential for deep-sea resource research and conservation. However, due to the poor image quality and insufficient image samples in the complex deep-sea imaging environment, resulting in poor detection results. Furthermore, most existing detection models accomplish high precision at the expense of increased complexity, and leading cannot be well deployed in the deep-sea environment. To alleviate these problems, a detection method for deep-sea organisms based on lightweight YOLOv5n is proposed. First, a lightweight YOLOv5n is created. The proposed image enhancement method based on global and local contrast fusion (GLCF) is introduced into the input layer of YOLOv5n to address the problem of color deviation and low contrast in the image. At the same time, a Bottleneck based on the Ghost module and simAM (GS-Bottleneck) is developed to achieve a lightweight model while ensuring sure detection performance. Second, a transfer learning strategy combined with knowledge distillation (TLKD) is designed, which can reduce the dependence of the model on the amount of data and improve the generalization ability to enhance detection accuracy. Experimental results on the deep-sea biological dataset show that the proposed method achieves good detection accuracy and speed, outperforming existing methods.

Pseudomonassin, a New Bioactive Ribosomally Synthesised and Post-Translationally Modified Peptide from Pseudomonas sp. SST3.

Genome mining and metabolomics have become valuable tools in natural products research to evaluate and identify potential new chemistry from bacteria. In the search for new compounds from the deep-sea organism, Pseudomonas sp. SST3, from the South Shetland Trough, Antarctica, a co-cultivation with a second deep-sea Pseudomonas zhaodongensis SST2, was undertaken to isolate pseudomonassin, a ribosomally synthesised and post-translationally modified peptide (RiPP) that belongs to a class of RiPP called lasso peptides. Pseudomonassin was identified using a genome-mining approach and isolated by means of mass spectrometric guided isolation. Extensive metabolomics analysis of the co-cultivation of Pseudomonas sp. SST3 and P. zhaodongensis SST2, Pseudomonas sp. SST3 and Escherichia coli, and P. zhaodongensis SST2 and E. coli were performed using principal component analysis (PCA) and orthogonal projections to latent structures discriminant analysis (OPLS-DA), which revealed potential new metabolites in the outlier regions of the co-cultivation, with other metabolites identified previously from other species of Pseudomonas. The sequence of pseudomonassin was completely deduced using high collision dissociation tandem mass spectrometry (HCD-MS/MS). Preliminary studies on its activity against the pathogenic P. aeruginosa and its biofilm formation have been assessed and produced a minimum inhibitory concentration (MIC) of 63 μg/mL and 28 μg/mL, respectively.

Latitudinal gradient and influencing factors of deep-sea particle export along the Kyushu-Palau Ridge in the Philippine Sea

The export of particulate organic matter (POM) to deep-sea is crucial for deep-sea ecosystems. However, in situ measurements of large-scale POM export flux are scarce in the tropical and subtropical western Pacific, leading to reliance on biogeochemical models or sediment trap data from a few stations. To address this gap, the underwater vision profiler was used to measure particulate density and to calculate particulate organic carbon (POC) fluxes along the Kyushu–Palau Ridge (KPR) in the Philippine Sea. The results revealed a significant latitudinal gradient of POC fluxes: 37 % of the POC output from 200 m depth was preserved to 2000 m in the Western Pacific Warm Pool and up to 51 % was preserved in the North Pacific Subtropical Gyre. The near-bottom POC fluxes north of 25°N (1.64 ± 0.80 mg m−2 d−1) were significantly higher than the average near-bottom value of the entire transect (0.60 ± 0.43 mg m−2 d−1). Multiple linear regression analysis showed that the chlorophyll concentration had a significant positive effect on the POC fluxes at all depths, except near the bottom, while local factors such as mesoscale eddies and the interaction effect between the topography and current velocity only had significant effects on the POC fluxes at depths of >2000 m. Particle size spectrum analysis revealed that particles ranging from 64 to 323 μm in size exerted a dominant influence on the increase in the POC fluxes in the near-bottom layers situated north of 25°N. These findings indicated that the spatial heterogeneity of POC fluxes in the western Pacific was governed not only by upper ocean primary productivity but also by mesoscale processes, current velocity, and topography. These results provided crucial fundamental information for cartography of the distribution and simulation of the dynamics of deep-sea organisms along the KPR in the Philippine Sea.

A new species of Janiralata Menzies, 1951 (Isopoda: Janiridae) from Japanese bathyal waters, with a review of the associations with invertebrates among the species of Janiralata

Abstract Isopods of the genus Janiralata Menzies, 1951 (Asellota: Janiridae) are known from shallow and deep waters of the Northern Hemisphere. Most species are free-living, but some are symbiotic on the surface of other benthic invertebrates. We obtained from three beam- and four otter-trawl hauls 18 Janiralata asellote specimens from the bathyal zone off the Pacific coasts of Tohoku, northeastern Japan. Partial nucleotide sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene (505 bp) were determined for 16 of the 18 collected specimens. Non-significant genetic differences (&amp;lt; 0.8%) indicated that the individuals were conspecifics. Morphological analysis indicated that all the specimens belonged to a single species, Janiralata planasp. nov. based on the unique morphology of the anterolateral and distolateral projections on the head and pleotelson, surface and lateral margins of the body, antennula article 1, and of the male pleopod 1. Six of the 18 collected specimens were found attached to the surface of an unidentified sea anemone (Hormathiidae), ten to the solasterid starfish Crossaster borealis Fisher, 1906 and two were obtained from the bottom sediment. Three COI haplotypes of the new species were shared by individuals from two neighboring sites, which suggests that genetic isolation occurs on a relatively narrow horizontal scale, although the bathymetric distribution range was rather wide. We describe a case study of the geographic and bathymetric distributions of an asellote species with low dispersal ability and its genetically differentiated populations. Such approach could help elucidate the diversity and distribution of deep-sea organisms and their diversification processes.

Deep sea nature-based solutions to climate change

The deep sea (below 200 m depth) is the largest carbon sink on Earth. It hosts abundant biodiversity that underpins the carbon cycle and provides provisioning, supporting, regulating and cultural ecosystem services. There is growing attention to climate-regulating ocean ecosystem services from the scientific, business and political sectors. In this essay we synthesize the unique biophysical, socioeconomic and governance characteristics of the deep sea to critically assess opportunities for deep-sea blue carbon to mitigate climate change. Deep-sea blue carbon consists of carbon fluxes and storage including carbon transferred from the atmosphere by the inorganic and organic carbon pumps to deep water, carbon sequestered in the skeletons and bodies of deep-sea organisms, carbon buried within sediments or captured in carbonate rock. However, mitigating climate change through deep-sea blue carbon enhancement suffers from lack of scientific knowledge and verification, technological limitations, potential environmental impacts, a lack of cooperation and collaboration, and underdeveloped governance. Together, these issues suggest that deep-sea climate change mitigation is limited. Thus, we suggest that a strong focus on blue carbon is too limited a framework for managing the deep sea to contribute to international goals, including the Sustainable Development Goals (SDGs), the Paris Agreement and the post-2020 Biodiversity Goals. Instead, the deep sea can be viewed as a more holistic nature-based solution, including many ecosystem services and biodiversity in addition to climate. Environmental impact assessments (EIAs), area-based management, pollution reduction, moratoria, carbon accounting and fisheries management are tools in international treaties that could help realize benefits from deep-sea, nature-based solutions.