Pandalus Platyceros Research Articles

Ground Reaction Forces and Energy Exchange During Underwater Walking.

Underwater walking was a crucial step in the evolutionary transition from water to land. Underwater walkers use fins and/or limbs to interact with the benthic substrate and produce propulsive forces. The dynamics of underwater walking remain poorly understood due to the lack of a sufficiently sensitive and waterproof system to measure substrate reaction forces (SRFs). Using an underwater force plate (described in our companion paper), we quantify SRFs during underwater walking in axolotls (Ambystoma mexicanum) and Spot prawn (Pandalus platyceros), synchronized with videography. The horizontal propulsive forces were greater than the braking forces in both species to overcome hydrodynamic drag. In axolotls, potential energy (PE) fluctuations were far smaller than kinetic energy (KE) fluctuations due to high buoyant support (97%), whereas the magnitudes were similar in the prawn due to lower buoyant support (93%). However, both species show minimal evidence of exchange between KE and PE, which, along with the effects of hydrodynamic drag, is incompatible with inverted pendulum dynamics. Our results show that, despite their evolutionary links, underwater walking has fundamentally different dynamics compared with terrestrial walking and emphasize the substantial consequences of differences in body plan in underwater walking.

Transcriptome analysis of hepatopancreas in penaeus monodon under acute low pH stress

The decrease of seawater pH can affect the metabolism, acid-base balance, immune response and immunoprotease activity of aquatic animals, leading to aquatic animal stress, impairing the immune system of aquatic animals and weakening disease resistance, etc. In this study, we performed high-throughput sequencing analysis of the hepatopancreas transcriptome library of low pH stress penaeus monodon, and after sequencing quality control, a total of 43488612–56271828 Clean Reads were obtained, and GO annotation and KEGG pathway enrichment analysis were performed on the obtained Clean Reads, and a total of 395 DEGs were identified. we mined 10 differentially expressed and found that they were significantly enriched in the Metabolic pathways (ko01100), Biosynthesis of secondary metabolites (ko01110), Nitrogen metabolism (ko00910) pathways, such as PIGA, DGAT1, DGAT2, UBE2E on Metabolic pathways; UGT, GLT1, TIM genes on Biosynthesis of secondary metabolites; CA, CA2, CA4 genes on Nitrogen metabolism, are involved in lipid metabolism, induction of oxidative stress and inflammation in the muscular body of spot prawns. These genes play an important role in lipid metabolism, induction of oxidative stress and inflammatory response in the muscle of the shrimp. In summary, these genes provide valuable reference information for future breeding of low pH-tolerant shrimp.

Micro-Probe Potentiometric pH Sensor for Detection of Amplification in the LAMP Assay for White Spot Syndrome Virus (WSSV) in Shrimps

A novel application of pH sensors is in the detection of amplification in nucleic acid-based methods for diagnosis of organisms. The detection is based on the production of hydrogen ions during the amplification process. In this study, a micro-probe potentiometric sensor for pH was fabricated and applied in the reagentless detection of the White Spot Shrimp Virus (WSSV) through the loop-mediated isothermal amplification (LAMP) technique. The pH micro-probe contained a pencil graphite modified with polypyrrole nanotubes through galvanostatic electrodeposition in the presence of methyl orange (MO). Electropolymerization parameters and potentiometric measurements parameters were optimized to obtain maximum sensitivity. The probe was characterized using Field Emission–Scanning Electron Microscopy (FE-SEM) and Fourier Transform-Infrared (FT-IR) Spectroscopy. The sensor showed a sub-Nernstian response (−45.5 mV/pH) at pH range 2–8 and LOD of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${5.19}\times {10}^{-{8}}$ </tex-math></inline-formula> M; with minimum hysteresis ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula> m = ± 1.27 mV/pH), and low potential drift (±1.00 mV, pH 8). The probe was used to measure the pH of the microliter-volume reaction mixture at the start and at the end of the LAMP assay for WSSV. The probe detected pH change ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta $ </tex-math></inline-formula> pH = −0.675) that occurred during the LAMP assay. This behavior correlated well with the results of fluorescence detection of the LAMP assay kit using SYBR Safe® DNA gel stain. A high diagnostic sensitivity (93.8%) and specificity (100%) was observed. The fabricated potentiometric sensor showed promising result in monitoring positive LAMP reaction through measurement of pH. This provides a method to diagnose shrimp samples with WSSV that is rapid, easy-to-operate, and cost-effective.

The complete mitochondrial genome of the spot prawn,Pandalus platycerosBrandt in von Middendorf, 1851 (Decapoda: Caridea: Pandalidae), assembled from linked-reads sequencing

AbstractPandalus platyceros Brandt in von Middendorf, 1851, the spot prawn, is a commercially important pandalid shrimp that sustains a small fishery in the northeastern Pacific Ocean. We report, for the first time, the complete mitochondrial genome of P. platyceros, while also testing whether linked-reads sequencing (10X Genomics) data can be used to assemble complete and accurate mitochondrial genomes. The pipeline GetOrganelle assembled and circularized the complete mitochondrial chromosome of P. platyceros with an average coverage of 28.2x from a dataset of 5 M pairs of linked reads. The AT-rich mitochondrial genome of P. platyceros is 16,628 bp in length and comprised of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes, and 24 transfer RNA genes. One copy of all tRNA genes was present, except for tRNA-G, which had three copies. A single 1,077 bp-long intergenic space was assumed to be the D-loop/Control region. Selective pressure analysis indicated the PCGs were under purifying selection, although levels differed among genes. The highest KA:KS ratios were found in nad4 and nad4l, suggesting weaker purifying selection and environmental constraints on these genes. The KA:KS ratios for cob and cox1 were a magnitude lower than the ratios in other PCGs, suggesting strong purifying selection acting upon these genes. A maximum likelihood phylogenetic analysis based on all PCGs that included a total of 91 species of shrimps supported the monophyly of the infraorder Caridea and family Pandalidae. Furthermore, the monophyly of other caridean families, including Alvinocaridae, Atyidae, Thoridae, Lysmatidae, and Palaemonidae was also supported by the same analysis. Our results thus suggest that mitochondrial PCGs have enough phylogenetic information to resolve relationships at high taxonomic levels (families) in Caridea. This study contributes new genomic resources for this commercially important species and demonstrates that linked-reads sequencing can be used to assemble accurate mitochondrial genomes.

Spot prawn parasite infection

This datasheet on spot prawn parasite infection covers Identity, Associated Diseases, Pests or Pathogens, Hosts/Species Affected.

Protandric Transcriptomes to Uncover Parts of the Crustacean Sex-Differentiation Puzzle

Hermaphrodite systems offer unique opportunities to study sexual differentiation, due to their high degree of sexual plasticity and to the fact that, unlike gonochoristic systems, the process is not confined to an early developmental stage. In protandric shrimp species, such as Hippolyte inermis and Pandalus platyceros, male differentiation is followed by transformation to femaleness during adulthood. The mechanisms controlling sexual differentiation have not been fully elucidated in crustaceans, but a key role has been attributed to the insulin-like hormone (IAG) produced by the androgenic gland (AG), a crustacean masculine endocrine organ. To uncover further transcriptomic toolkit elements affecting the sexual differentiation of H. inermis, we constructed eye and whole body RNA libraries of four representative stages during its protandric life cycle (immature, male, young female and mature female). The body libraries contained transcripts related to the reproductive system, among others, while the eye libraries contained transcripts related to the X-organ-sinus gland, a central endocrine complex that regulates crustacean reproduction. Binary pattern analysis, performed to mine for genes expressed differentially between the different life stages, yielded 19,605 and 6,175 transcripts with a specific expression pattern in the eye and body, respectively. Prominent sexually biased transcriptomic patterns were recorded for the IAG and vitellogenin genes, representing, respectively, a key factor within the masculine IAG-switch, and a precursor of the yolk protein, typical of feminine reproductive states. These patterns enabled the discovery of novel putative protein-coding transcripts exhibiting sexually biased expression in the H. inermis body and eye transcriptomes of males and females. Homologs to the above novel genes have been found in other decapod crustaceans, and a comparative study, using previously constructed transcriptomic libraries of another protandric shrimp, P. platyceros, showed similar sexually biased results, supporting the notion that such genes, mined from the H. inermis transcriptome, may be universal factors related to reproduction and sexual differentiation and their control in other crustaceans. This study thus demonstrates the potential of transcriptomic studies in protandric species to uncover unexplored layers of the complex crustacean sex-differentiation puzzle.

Lethal and sublethal effects of the anti‐sea lice formulation Salmosan® on the Pacific spot prawn (Pandalus platyceros)

AbstractThe effects of the aquaculture chemotherapeutant Salmosan® (active ingredient [a.i.]: azamethiphos) were examined in Pacific spot prawns (Pandalus platyceros) at three temperatures (5, 11, and 17°C). Post‐molt prawns were more sensitive to Salmosan® than intermolt prawns; repeated (3x) 1‐hr LC50 values for post‐molt prawns ranged from 17 (9.3–31 95% confident intervals) to 40 (25–63) μg/L a.i. while intermolt prawns survived 3 × 1‐hr exposures up to 100 μg/L a.i. Using LC50 values, Salmosan® was approximately 2.4 times more toxic at 17 versus 5°C. Temperature significantly altered chemosensory and locomotory behaviors in intermolt prawns with the highest activity at the intermediate temperature. Significant decreases in antennule flicking (84 and 104% over controls) were seen at 17°C after 3 × 1‐hr pulse exposures to 50 and 100 μg/L a.i., respectively. Temperature, but not Salmosan®, affected molting success: at 17°C significantly lower survival was seen during ecdysis (60% of those at 5°C) and at 5°C, molt time was longer (41 ± 3 days) compared to 11°C (34 ± 4 days) or 17°C (21 ± 4 days). Life stage (molt status) and environmental parameters (temperature) alter the effects of Salmosan® to non‐target spot prawns.

Biological traits of the spot prawn Pandalus platyceros Brandt, 1851 (Decapoda, Caridea) at its southernmost distribution limit

Abstract The spot prawn fishery, targeting Pandalus platyceros, has failed to prove commercially viable on the Mexican Pacific coast. A survey was carried out off the northwestern coast of Baja California, at depths of 140-180 m. The objective was to describe the biological traits of the species to test the hypothesis that warmer water stimulates higher growth parameters. An average model was estimated that anticipated an inverted exponential growth curve, consequently the growth parameters of the Von Bertalanffy model were obtained as , carapace length (CL) and . Being a protandric hermaphrodite, the transition size was estimated at 40.8 mm CL. The results challenged the hypothesis that P. platyceros grows faster in temperate environments than in cold environments.

Elemental and structural changes associated with white spot formation in sun‐dried Pacific white shrimp shells

AbstractStructural and elemental properties of dried Pacific white shrimp (WSS) (Litopenaeus vannamei) shell having the white spots were compared with non‐white spot shrimp (NWSS) shell. Based on X‐ray diffraction (XRD) analysis, both samples showed two characteristic peaks representing chitin. However, WSS sample had two additional major peaks at 2θ of 26.65 and 29.53º, which were related to quartz and calcite, respectively. Scanning electron microscope coupled with energy‐dispersive X‐ray spectrophotometer (SEM‐EDX) mapping showed the movement of various elements towards the exo‐ and endocuticle. The Raman spectroscopic study confirmed the formation of calcite crystals in the white spots. The looser chitin matrix was obtained for WSS as compared to that of NWSS as depicted in SEM micrographs. Therefore, the white spots developed in the shell were caused by the formation of calcite, which exhibited different structural arrangements and elemental positioning as compared to shrimp shell without white spots.

The IAG-Switch and Further Transcriptomic Insights Into Sexual Differentiation of a Protandric Shrimp

The insulin-like androgenic gland hormone (IAG) secreted from the androgenic gland (AG) is a unique endocrine controller (the IAG-switch) of crustacean sexual differentiation. However, while previous studies of the IAG-switch focused mainly on sexual differentiation at early developmental stages of gonochoristic species, this mechanism is yet to be deciphered during naturally occurring sexual shifts in hermaphrodite species. The Northern spot shrimp, Pandalus platyceros, is a protandric hermaphrodite species, native to the North Pacific Ocean. We collected four stages of spot shrimp in Southeast Alaska including: juveniles, adult males, transitionals and adult females. The AG was dissected from each stage and characterized histologically. Additionally, the IAG mRNA was sequenced. The function of the IAG-switch during the life history of this protandric species was demonstrated through monitoring IAG gene expression. Transcript levels were highest at the juvenile stage, then decreased significantly in mature males and became negligible in the transitional and female stages. Moreover, manipulating the IAG-switch via IAG loss of function in males through RNAi, induced the expected masculine to feminine sexual transformation that naturally occurs in this species. This included reduction in IAG transcript levels in males, elevation of vitellogenin gene expression in hepatopancreas and transformation of the gonad from an ovotestis containing both ovarian and testicular tissue to a true ovary with vitellogenic oocytes. Furthermore, a transcriptomic library from tissues associated with the endocrine axis upstream and downstream the IAG-switch yielded 1,801, 1,707, 1,946 and 182 differentially expressed genes between males, transitionals and females in the AG, eyestalk, gonad and hepatopancreas, respectively. Among these genes, the transcriptional pattern of six of them (all of them in the AG), between males, transitionals and females, had similar or inverted transcriptional pattern to that of IAG in P. platyceros. Five of these putatively IAG-switch associated genes are downregulated and one is upregulated throughout the P. platyceros shift from maleness to femaleness. Homolog protein sequences for the above novel genes were found in 17 other decapod species suggesting that they might represent conserved factors associated with the IAG-switch and involved in universal crustacean sexual differentiation mechanisms.

The protandric life history of the Northern spot shrimp Pandalus platyceros: molecular insights and implications for fishery management

The Northern spot shrimp, Pandalus platyceros, a protandric hermaphrodite of commercial importance in North America, is the primary target species for shrimp fisheries within Southeast Alaska. Fishery data obtained from the Alaska Department of Fish and Game indicate that spot shrimp populations have been declining significantly over the past 25 years. We collected spot shrimps in Southeast Alaska and measured reproductive-related morphological, gonadal and molecular changes during the entire life history. The appendix masculina, a major sexual morphological indicator, is indicative of the reproductive phase of the animal, lengthening during maturation from juvenile to the male phase and then gradually shortening throughout the transitional stages until its complete disappearance upon transformation to a female. This morphological change occurs in parallel with the degeneration of testicular tissue in the ovotestis and enhanced ovarian vitellogenesis. Moreover, we obtained the entire mRNA sequence of the yolk protein precursor, vitellogenin, and monitored its transcript levels throughout the entire shrimp life-cycle. Vitellogenin transcript levels in the hepatopancreas increased in the early transitional stage until reaching a peak prior to extruding eggs. Such transcriptomic analyses, coupled with a comprehensive description of the gonad, external sex characters and timing of the reproductive life history of spot shrimps contribute to a better understanding of the hermaphroditic reproduction process in the cold Southeast Alaskan waters. This knowledge can contribute to a revision of current conservation efforts to maintain wild populations sustainable for both commercial and ecological considerations.

Bycatch of rockfish in spot prawn traps and estimated magnitude of trap loss in Washington waters of the Salish Sea

Derelict fishing gear is a known stressor to rockfish populations in the Washington waters of the Salish Sea, including two species currently federally protected under the Endangered Species Act. In Washington and British Columbia, rockfish bycatch in actively fished (non-derelict) prawn traps has been documented in spot prawn test fisheries conducted by state and provincial government, and both live and dead rockfish have been found in derelict prawn traps encountered during derelict fishing gear removal operations in Washington. This study calculates rockfish bycatch rates in actively fishing prawn traps and provides preliminary trap loss rates for both commercial and recreational fisheries. Rockfish bycatch rates were determined through analysis of Washington Department of Fish and Wildlife (WDFW) Spot Prawn Test Fishery Data collected from 2004 to 2013. Data from WDFW creel surveys were used to update preliminary prawn trap loss rates. Interviews with WDFW marine enforcement officers were conducted to estimate the number of lost traps that are recovered before becoming derelict. The overall rockfish catch rates in Washington waters of the Salish Sea were 0.023 rockfish per trap drop, with considerable spatial and temporal variability. The lowest catch rates were consistently seen in Marine Area 7 (San Juan Islands and North Puget Sound); while the highest catch rates were seen in Marine Area 11 (south-central Puget Sound). The trap loss rate estimated for the recreational fishery is 2.33% of all traps fished. We estimate that over the years 2012 and 2013 an average of 653 recreational prawn traps became derelict each year. The accumulation of derelict prawn traps has a mostly unknown effect on benthic habitats of Puget Sound, which warrants additional research. While rockfish bycatch and prawn trap loss rates reported here are low, our findings support evaluating methods to reduce rockfish encounters with prawn traps.

Online Monitoring of Shrimp Aquaculture in Bangka Island Using Wireless Sensor Network

In this paper, it will be described the design and realization of online water quality monitoring system based on wireless sensor network (WSN). The new system has been implemented specifically to monitor parameters Dissolved Oxygen (DO), pH and temperature in one spot shrimp aquaculture in Bangka island. The aim was to create suitable water conditions for shrimp aquaculture and save the cost of energy consumption using an automated aeration system, by maintaining the value of the DO above 5 mg/L. On the other hand, water quality data collected from sensor measurements are sent to a data logger using WSN, and then the data is sent to a data center using cellular network (GPRS) such that this data can be viewed using the website. The experimental results show that the system has great prospects and can be used for shrimp aquaculture by providing information that is relevant and timely. The resulting data the collection can be used for research and analysis.

Characterizing the sponge grounds of Grays Canyon, Washington, USA

Deep-sea sponge grounds are relatively understudied ecosystems that may provide key habitats for a large number of fish and invertebrates including commercial species. Glass sponge grounds have been discovered from the tropics to polar regions but there are only a few places with high densities of dictyonine sponges. Dictyonine glass sponges have a fused skeleton, which stays intact when they die and in some areas the accumulation of successive generations of sponges leads to the formation of reefs. In 2010 and 2016, we surveyed an area near Grays Canyon in Washington, USA, where dense aggregations of glass sponges and potential sponge reefs were discovered in 2007. Our primary aims were to make a preliminary assessment of whether the glass sponges form reefs at this location, characterize the sponge assemblage present at this site and examine associations between the sponges and commercially important species. Multibeam mapping and sub-bottom profiling indicate that the glass sponges at this site do not form reefs and are mostly attached to hard substrates. Analysis of photographs collected by an autonomous underwater vehicle and samples collected by a remotely operated vehicle guided by telepresence revealed the presence of two abundant dictyonine sponge species at this site, Heterochone calyx and Aphrocallistes vastus (mean densities = 1.43 ± 0.057 per 10m2, max = 24 per 10m2). We also observed a large number of non-reef-building glass sponges and various demosponges including a potentially new species in the genus Acarnus. A diverse fish assemblage was recorded at this site including eight species of rockfish. Rockfish abundance was positively related to sponge abundance. Spot prawns (Pandalus platyceros) were also abundant and were strongly associated with sponges. Despite not finding sponge reefs, this is an ecologically significant area. Further research is necessary to determine the environmental factors that give rise to the abundance of large dictyonine sponges at this location and also to determine if other similar sponge grounds exist along the west coast of the United States.

Evaluating the promise and pitfalls of a potential climate change-tolerant sea urchin fishery in southern California.

Marine fishery stakeholders are beginning to consider and implement adaptation strategies in the face of growing consumer demand and potential deleterious climate change impacts such as ocean warming, ocean acidification, and deoxygenation. This study investigates the potential for development of a novel climate change-tolerant sea urchin fishery in southern California based on Strongylocentrotus fragilis (pink sea urchin), a deep-sea species whose peak density was found to coincide with a current trap-based spot prawn fishery (Pandalus platyceros) in the 200-300-m depth range. Here we outline potential criteria for a climate change-tolerant fishery by examining the distribution, life-history attributes, and marketable qualities of S. fragilis in southern California. We provide evidence of seasonality of gonad production and demonstrate that peak gonad production occurs in the winter season. S. fragilis likely spawns in the spring season as evidenced by consistent minimum gonad indices in the spring/summer seasons across 4 years of sampling (2012-2016). The resiliency of S. fragilis to predicted future increases in acidity and decreases in oxygen was supported by high species abundance, albeit reduced relative growth rate estimates at water depths (485-510 m) subject to low oxygen (11.7-16.9 µmol kg-1) and pHTotal (<7.44), which may provide assurances to stakeholders and managers regarding the suitability of this species for commercial exploitation. Some food quality properties of the S. fragilis roe (e.g. colour, texture) were comparable with those of the commercially exploited shallow-water red sea urchin (Mesocentrotus franciscanus), while other qualities (e.g. 80% reduced gonad size by weight) limit the potential future marketability of S. fragilis. This case study highlights the potential future challenges and drawbacks of climate-tolerant fishery development in an attempt to inform future urchin fishery stakeholders.

Comparison of Faunal Scavenging of Submerged Carrion in Two Seasons at a Depth of 170 m, in the Strait of Georgia, British Columbia.

The taphonomy of carcasses submerged in the ocean is little understood, yet it is extremely important ecologically and forensically. The objectives of this study were to determine the fate of pig carcasses as human proxies in the Strait of Georgia at 170 m in spring and fall. Using Ocean Networks Canada’s Victoria Experimental Network Underseas (VENUS) observatory, two carcasses per season were placed under a cabled platform hosting a webcam and instruments measuring water chemistry. Two minutes of video were recorded every 15 min. In spring, Lyssianassidae amphipods and Pandalus platyceros were immediately attracted and fed on the carcasses, the amphipods removed the bulk of the soft tissue from the inside whilst the shrimp shredded the skin and tissue. The carcasses were skeletonized on Days 8 and 10. In fall, Metacarcinus magister was the major scavenger, removing most of the soft tissue from one carcass. Amphipods did not arrive in large numbers until Day 15, when they skeletonized the scavenged carcass by Day 22 and the less scavenged carcass by Day 24. Amphipods remained for some days after skeletonization. This skeletonization was very different from previous experiments at different depths and habitats. Such data are very valuable for predicting preservation, planning recoveries, and managing family expectations.

Ecophysiological limits to aerobic metabolism in hypoxia determine epibenthic distributions and energy sequestration in the northeast Pacific ocean

AbstractExpansion of oxygen deficient waters (hypoxia) in the northeast Pacific Ocean (NEP) will have marked impacts on marine life. The response of the resident communities will be a function of their ecophysiological constraints in low oxygen, although this remains untested in the NEP due to a lack of integrative studies. Here, we combine in situ surveys and lab‐based respirometry experiments were conducted on three indicator species (spot prawnPandalus platyceros, slender soleLyopsetta exilis, squat lobsterMunida quadrispina) of seasonally hypoxic systems in the NEP to test if metabolic constraints determine distributions and energy sequestration in a hypoxic setting. These experiments were integrated with a global review of critical oxygen levels (; lower threshold of aerobic metabolism) for crustaceans to determine if‐based hypoxia thresholds are different among ocean basins. Our results show that species‐specific differences inand standard metabolic rates (1) determine the lowest environmental oxygen ([O2]env) at which in situ populations occur, (2) result in disproportionate shifts in distributions among co‐occurring species during summer hypoxia expansion events, and (3) characterize shifts in megafaunal community respiration rates due to marked spatio‐temporal variability in [O2]env. Our results show that‐based hypoxia thresholds are significantly lower in the East Pacific Ocean relative to other major ocean basins, which suggests that the physiological response of local fauna to deoxygenation can be determined by the natural variability and oxygen exposure in a region. In order to establish realistic predictions on the biological consequences of marine deoxygenation, we suggest integrating metabolism‐based traits to calculate hypoxia thresholds for marine ecosystems.

Impact of Marine Submergence and Season on Faunal Colonization and Decomposition of Pig Carcasses in the Salish Sea.

Pig carcasses, as human proxies, were placed on the seabed at a depth of 300 m, in the Strait of Georgia and observed continuously by a remotely operated camera and instruments. Two carcasses were deployed in spring and two in fall utilizing Ocean Network Canada’s Victoria Experimental Network under the Sea (formerly VENUS) observatory. A trial experiment showed that bluntnose sixgill sharks could rapidly devour a carcass so a platform was designed which held two matched carcasses, one fully exposed, the other covered in a barred cage to protect it from sharks, while still allowing invertebrates and smaller vertebrates access. The carcasses were deployed under a frame which supported a video camera, and instruments which recorded oxygen, temperature, salinity, density, pressure, conductivity, sound speed and turbidity at per minute intervals. The spring exposed carcass was briefly fed upon by sharks, but they were inefficient feeders and lost interest after a few bites. Immediately after deployment, all carcasses, in both spring and fall, were very rapidly covered in vast numbers of lyssianassid amphipods. These skeletonized the carcasses by Day 3 in fall and Day 4 in spring. A dramatic, very localized drop in dissolved oxygen levels occurred in fall, exactly coinciding with the presence of the amphipods. Oxygen levels returned to normal once the amphipods dispersed. Either the physical presence of the amphipods or the sudden draw down of oxygen during their tenure, excluded other fauna. The amphipods fed from the inside out, removing the skin last. After the amphipods had receded, other fauna colonized such as spot shrimp and a few Dungeness crabs but by this time, all soft tissue had been removed. The amphipod activity caused major bioturbation in the local area and possible oxygen depletion. The spring deployment carcasses became covered in silt and a black film formed on them and on the silt above them whereas the fall bones remained uncovered and hence continued to be attractive to large numbers of spot shrimp. The carcass remains were recovered after 166 and 134 days respectively for further study.

Effects of submarine power transmission cables on a glass sponge reef and associated megafaunal community

We examined the effects of submarine power transmission cable installation and operation on glass sponge reef condition and associated megafauna. Video and still imagery were collected using a Remotely Operated Vehicle twice a year for 4 years following cable installation. The effects of cables on glass sponges were assessed by comparing sponge cover along fixed transects and at marked index sites. Megafauna counts along transects were used to explore the effects on associated community. We found no evidence of cable movement across the sponge reef surface. Live sponge cover was found to be consistently lower along cable transects and at cable index sites compared to controls. Live sponge cover was the lowest (55 ± 1.1% decrease) at cable index sites 1.5 years after installation and recovered to 85 ± 30.6% of the original size over the following 2 years. Our data suggest 100% glass sponge mortality along the direct cable footprint and 15% mortality in the surrounding 1.5 m corridor 3.5 years after cable installation. Growth rate of a new glass sponge was 1 and 3 cm/year in first and second year, respectively, and appeared to be seasonal. We observed a diverse megafaunal community with representatives from 7 phyla and 14 classes. Total megafauna, spot prawn, and other Arthropoda abundances were slightly lower along cable transects although the effect of cable presence was not statistically significant. The following measures could be taken to reduce the amount of damage to glass sponge reefs and associated fauna: routing the cable around reefs, whenever possible, minimizing cable movement across the surface of the reef at installation and routine operation, and assessing potential damage to glass sponges prior to decommissioning.

A comparison of nanoindentation creep deformation characteristics of hydrothermal vent shrimp (Rimicaris exoculata) and shallow water shrimp (Pandalus platyceros) exoskeletons

Abstract