Sea Urchin Strongylocentrotus Droebachiensis Research Articles

Mechanisms of stability of rhodolith beds: sedimentological aspects

Rhodolith beds are highly diverse benthic communities organized around the physical structure and primary productivity of red coralline algae. Despite a worldwide distribution and growing recognition that rhodolith beds are important calcium carbonate (CaCO₃) bio-factories, little is known of the factors and processes that regulate their structure, function, and stability. One prevalent and largely untested paradigm is that beds develop in environments where water motion is strong enough to prevent burial by sediments. Observations over seven months and three weeks in the centre and near the upper and lower margins of a Newfoundland rhodolith (Lithothamnion glaciale) bed, as well as a laboratory mesocosm experiment with rhodoliths and dominant macrofauna from the bed, were used to characterize, parse, and model spatial and temporal variation in rhodolith sediment load (RSL) and movement among presumably important abiotic and biotic factors. RSL and movement were largely mediated by a few dominant benthic invertebrates. Hydrodynamic forces were insufficient to displace rhodoliths. Daisy brittle stars (Ophiopholis aculeata) and small common sea stars (Asterias rubens) contributed to dislodgement of sediment from rhodoliths. Large green sea urchins (Strongylocentrotus droebachiensis) easily displaced rhodoliths in mesocosms. Results provide the first quantitative demonstration that rhodolith beds need not be exposed to threshold hydrodynamic conditions to avoid burial. Beds can simply occur in areas where burial is unlikely because of low sedimentation rates. In such cases, select resident bioturbators operating simultaneously at different spatial scales (within and outside rhodoliths) appear to suffice to maintain RSL below lethal quantities, contributing to stability of beds.

Will altered climate affect a discrete population of the sea urchin Strongylocentrotus droebachiensis?

The Green sea urchin Strongylocentrotus droebachiensis is a cold-water species that in the 70s and 80s was the main culprit in the major grazing of macrophytes in the Norwegian fjords and coastal areas.Recent reports have questioned a decline in the S. droebachiensis in the Oslofjord, similar to what was observed to occur in the Norwegian coastal population of S. droebachiensis after the 1990s. In surveys from 2013 we collected data on urchin density, test diameter, early urchin settlement and Gonad Index and created a framework in order to investigate if the current Inner Oslofjord populations of S. droebachiensis are different from surveys conducted in 1979 and 1992. This study found significant differences in density, diameter and settlement over time. Highest density in 1992 was at 10 and 15m, while being at 20m in 2013. Urchin diameter at the station with most urchins was on average 5cm in 1992 compared to 3cm in 2013. Settlement differed both between the number of settlers between 1992 and 2013, and season for highest settlement (summer in 1992, and autumn in 2013). The inner Oslofjord sea urchin data indicate a still healthy population, although environmental data (as temperature and salinity) have changed to less favorable conditions for this species.

Optimization of (Poly)Hydroxynaphthoquinone Extraction from Shells of Strongylocentrotus Droebachiensis Sea Urchins

Extraction of lipophilic substances from shells and spines of green sea urchins (Strongylocentrotus droebachiensis) was studied. It was found that the extraction time had the greatest influence on the yield of lipophilic substances whereas temperature and extraction modulus had insignificant effects. Ethanol (95%) was chosen as the extractant affording the maximum amount of lipophilic substances. Optimization of the defatting step established that the maximum yield of lipophilic substances (1.2%) was attained after extraction for 3 h at 55°C with a 1:8 raw-material—extractant ratio. Free fatty acids (57%), phospholipids (~7%), diglycerides, sterols, triglycerides, and hydrocarbons were detected in the lipophilic extract. Phospholipids in the lipophilic extract were represented mainly by phosphatidylcholine. Lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidylinositol, and phosphatidylethanolamine were detected in trace quantities. The (poly)hydroxynaphthoquinone pigment content after purifying the raw material of lipophilic substances was 98.5% according to HPLC.

Invasive tunicate restructures invertebrate community on fishing grounds and a large protected area on Georges Bank

Marine invasive species can profoundly alter ecosystem processes by displacing native species and changing community structures. The invasive tunicate Didemnum vexillum was first found on the northern edge of Georges Bank in 1998. It can form encrusting colonies on gravel substrates that are also a preferred habitat for a number of other invertebrates. In this study we used data collected via HabCam, a vessel-towed underwater imaging system, to investigate the distribution of D. vexillum and its relationship to other epibenthic macroinvertebrates in a portion of Georges Bank that includes fishing grounds and an area protected from bottom-fishing. This novel technology provides imaging of epibenthic species distributions in areas of the benthic environment that were previously unobservable. We found that D. vexillum density is negatively correlated with the Atlantic sea scallop (Placopecten magellanicus), barnacles (genus Balanus), the tube anemone (genus Cerianthus), the green sea urchin (Strongylocentrotus droebachiensis), the globular sponge of the genus Polymastia, and Bryozoa. However D. vexillum is positively correlated with Cancer spp. Crabs, the tube forming polychaete, Filograna implexa, and Asterias spp. sea stars. The hypothesis that D. vexillum restructures the invertebrate community is supported by principal components analysis, revealing it as a primary driver of variation in the community when present. Additionally, there is an effect of the closed area as compared to fishing grounds on the structure of the invertebrate community and the abundance of certain species as consistent with previous studies, bottom-fishing affects invertebrate community structure. Principal components analysis revealed that bottom-fishing also appears to weaken clustering among species in the invertebrate community as compared to the community structure in the closed area. Biodiversity in high gravel sites of the epibenthic environment, as measured by the Shannon diversity index, also declined with increasing D. vexillum percent cover, while the open and closed areas were not significantly different in their level of biodiversity. D. vexillum appears to be the key driver of biodiversity decline in the epibenthos when present, rather than other processes such as direct disturbance and extraction from dredging. This research evaluates ecological responses to the presence of an invasive tunicate and suggests that this invasive species is a major force in shaping the ecological interactions in invaded areas.

Оптимизация технологического процесса извлечения полигидроксинафтохинона из панциря морских ежей <i>Strongylocentrotus droebachiensis</i>

Изучен процесс экстракции липофильных веществ из панциря с иглами зеленого морского ежа. Установлено, что наибольшее влияние на выход липофильных веществ оказывает время экстракции, в то время как температура и модуль экстракции оказывают незначительное влияние. В качестве экстрагента, извлекающего максимальное количество липофильных веществ, выбран 95 % этиловый спирт. В результате оптимизации процесса обезжиривания установлено, что максимальный выход липофильных веществ (1,2 %) достижим при обработке сырья в течение 3 ч, при температуре экстракции 55 °C и соотношении сырьё — экстрагент (1:8). В липофильном экстракте обнаружены 57 % свободных жирных кислот, около 7 % фосфолипидов, диглицериды, стерины, триглицериды и углеводороды. Фосфолипиды в липофильном экстракте представлены преимущественно фосфатидилхолином. Лизофосфатидилхолин, лизофосфатидилэтаноламин, фосфатидилинозитол и фосфатидилэтаноламин обнаружены в следовых количествах. Содержание полигидроксинафтохинонового пигмента после очистки сырья от липофильных веществ по данным ВЭЖХ составило 98,5 %.

Efficiency of trap type, soak time and bait type and quantities for harvesting the sea urchin Strongylocentrotus droebachiensis (Müller) in Norway

Two trials were conducted to test the following: i) the efficacy of three sea urchin trap types ii) the effect of trap soak time (1-8days) and iii) the efficacy of two bait types fed at various quantities. The results showed that the round flat, hinged trap design was the most effective and had the highest catch rate. The highest catch rate occurred after 5days and the authors recommend 3–8day soak periods for commercial trapping operations. The trials showed that fish bait attracted much higher diversity and quantities of by-catch than algae baits. The more bait stations (of either algae or fish bait) used the greater the catch. However, increasing the number of bait stations also increases the cost and time required to set the bait stations. The authors recommend a minimum of two bait stations per urchin trap to optimize CPUE. Comparisons of trap catch rate and associated costs and logistics indicate that trapping is an economically viable alternative to SCUBA diving and other harvest techniques in Norway.

Articulated coralline algae provide a spatial refuge to juvenile sea urchins from predatory crabs

Coralline algae provide settlement cues, food, and biotic structure for benthic marine invertebrates in intertidal and subtidal habitats. Here, we present evidence from laboratory experiments that juvenile sea urchins Strongylocentrotus droebachiensis (1.0–3.0 mm test diameter) are chemically attracted to articulated coralline algae Corallina vancouveriensis in the San Juan Archipelago (Washington, USA), resulting in movement of sea urchins into the algae. This behavior significantly reduced sea urchin mortality in the presence of predatory crabs Pagurus spp. and Cancer oregonensis as compared to treatments with no algae. In addition, we tested predation rates of various benthic predators from intertidal and subtidal habitats, and found that crabs were the most voracious predators of juvenile sea urchins. Our results indicate that C. vancouveriensis provides a spatial refuge to juvenile sea urchins from predatory crabs, and may facilitate recruitment into sea urchin populations by enhancing juvenile survival.

Ontogenetic shifts in swimming capacity of echinoderm propagules: a comparison of species with planktotrophic and lecithotrophic larvae

While developmental strategies can modulate the dispersal and recruitment of marine benthic species, the significance and drivers of propagule motility throughout ontogeny remain incompletely understood. Species with lecithotrophic (non-feeding) development are rarely studied, despite their predominance in some taxa, including echinoderms. Quantification of the swimming capacity (i.e. speed and trajectory) of early life history stages and its variability with environmental factors is required to improve the ability to predict population connectivity and assess trade-offs associated with complex life histories. In general, lecithotrophic larvae of echinoderms are ascribed weak swimming abilities relative to planktotrophic larvae, although explicit measures are scarce. Here, we explored selected metrics of swimming capacity in four co-occurring species of North Atlantic echinoderms displaying different types of pelagic development: planktotrophs represented by the sea star Asterias rubens and the sea urchin Strongylocentrotus droebachiensis, and lecithotrophs represented by the sea star Crossaster papposus and the sea cucumber Cucumaria frondosa. Swimming was characterized in still water based on the horizontal speed and path straightness of early life-history stages, from late blastula (hatched embryo) to late-stage larva. We tested the hypotheses that swimming capacity of propagules increases with progression through developmental stages and with increasing seawater temperature. Swimming speed increased with ontogeny in two of the four species (A. rubens and C. papposus) and with temperature in all species, although the effects of temperature were not uniform across life stages. The fastest swimming speeds across all species and temperatures were recorded in lecithotrophic propagules (i.e. max speed 1.2 mm s− 1 in the brachiolaria of C. papposus), whereas propagules of species with planktotrophic development displayed faster relative speeds (body lengths s− 1). Relative speeds increased with temperature in all tested species except C. papposus. Swimming paths typically increased in straightness from early to later developmental stages, and also became straighter with increased temperature in most species, except in C. papposus where they became more circular and complex. In general, planktotrophic and lecithotrophic propagules had similar swimming capacities when tested at the same level of increased temperature, though several stage-specific differences were detected; propagules of species with planktotrophic development had greater relative speeds at the gastrula stage and greater path-corrected speeds at the larval stage. Swimming paths and swimming speeds were similar between propagules of species with planktotrophic development and lecithotrophic development, suggesting that phylogenetically conserved, ontogenetic patterns of swimming capacity (seen here between two sea stars) may supersede the contribution of larval nutritional mode.

Comparative stability of dimeric and monomeric pigments extracted from sea urchin Strongylocentrotus droebachiensis

Ultraviolet–visible spectroscopy and UPLC–DAD–MS were used for analysis of stability of ethanol solutions of ethylidene-6,6′-bis(2,3,7-trihydroxynaphthazarin) (ENZ), spinochrome dimer (SDM) and spinochrome D (SD) that were isolated from Strongylocentrotus droebachiensis. In the freshly prepared solution, the concentration of ENZ at pH 6.0 was at 6 fold less comparing to pH 1.6. The increase of pH up to 4.0 resulted to increase of SD concentration and to decrease of SDM concentration. After 48 h storage, both dimers showed the highest stability at pH 1.6, while the elevation of the pH solution up to 6.0 activates degradation of SDM and ENZ at 1.3 and 3.6 fold correspondingly. The concentration of SD after 48 h storage at the pH 1.6 was at two-fold less comparing to the initial concentration, and at the pH 6.0 – at 4 fold less. This study contributes to increasing the knowledge on the stability of the spinochrome pigments.

Silver nanoparticles and dissolved silver activate contrasting immune responses and stress-induced heat shock protein expression in sea urchin.

Using immune cells of sea urchin Strongylocentrotus droebachiensis in early development as a model, the cellular protective mechanisms against ionic and poly(allylamine)-coated silver nanoparticle (AgNPs; 14 ± 6 nm) treatments at 100 μg L-1 were investigated. Oxidative stress, heat shock protein expression, and pigment production by spherulocytes were determined as well as AgNP translocation pathways and their multiple effects on circulating coelomocytes. Sea urchins showed an increasing resilience to Ag over time because ionic Ag is accumulated in a steady way, although nanoAg levels dropped between 48 h and 96 h. A clotting reaction emerged on tissues injured by dissolved Ag (present as chloro-complexes in seawater) between 12 h and 48 h. Silver contamination and nutritional state influenced the production of reactive oxygen species. After passing through coelomic sinuses and gut, AgNPs were found in coelomocytes. Inside blood vessels, apoptosis-like processes appeared in coelomocytes highly contaminated by poly(allylamine)-coated AgNPs. Increasing levels of Ag accumulated by urchins once exposed to AgNPs pointed to a Trojan-horse mechanism operating over 12-d exposure. However, under short-term treatments, physical interactions of poly(allylamine)-coated AgNPs with cell structures might be, at some point, predominant and responsible for the highest levels of stress-related proteins detected. The present study is the first report detailing nano-translocation in a marine organism and multiple mechanisms by which sea urchin cells can deal with toxic AgNPs. Environ Toxicol Chem 2017;36:1872-1886. © 2016 SETAC.

Genomic Characterization of the Evolutionary Potential of the Sea Urchin Strongylocentrotus droebachiensis Facing Ocean Acidification.

Ocean acidification (OA) is increasing due to anthropogenic CO2 emissions and poses a threat to marine species and communities worldwide. To better project the effects of acidification on organisms’ health and persistence, an understanding is needed of the 1) mechanisms underlying developmental and physiological tolerance and 2) potential populations have for rapid evolutionary adaptation. This is especially challenging in nonmodel species where targeted assays of metabolism and stress physiology may not be available or economical for large-scale assessments of genetic constraints. We used mRNA sequencing and a quantitative genetics breeding design to study mechanisms underlying genetic variability and tolerance to decreased seawater pH (-0.4 pH units) in larvae of the sea urchin Strongylocentrotus droebachiensis. We used a gene ontology-based approach to integrate expression profiles into indirect measures of cellular and biochemical traits underlying variation in larval performance (i.e., growth rates). Molecular responses to OA were complex, involving changes to several functions such as growth rates, cell division, metabolism, and immune activities. Surprisingly, the magnitude of pH effects on molecular traits tended to be small relative to variation attributable to segregating functional genetic variation in this species. We discuss how the application of transcriptomics and quantitative genetics approaches across diverse species can enrich our understanding of the biological impacts of climate change.

Following the flow of ornithogenic nutrients through the Arctic marine coastal food webs

Arctic colonial seabirds are recognized as effective fertilizers of terrestrial ecosystems by delivering marine-origin nutrients to the vicinities of their nesting sites. A proportion of this ornithogenic matter is then thought to return to the sea and, concentrated within a smaller area, locally provides additional nutrients for the nearshore marine communities. The aim of this study was to assess the presence and impact of local ornithogenic enrichment on two important elements of the Arctic coastal food web: (1) the planktonic pathway originating in the surface water, and (2) the benthic pathway based on benthic primary production. We sampled two areas in Isfjorden (Spitsbergen): one located below a coastal mixed breeding colony of guillemots and kittiwakes, and a control area not influenced by the colony. Slightly higher nitrogen stable isotope ratios (δ15N) were found in particulate organic matter suspended in the surface water (POM), sedimentary organic matter (SOM) from outside the zone of dense kelp forest, and the predatory/scavenging whelks Buccinum sp. collected below the seabird colony (the components recognized as following the planktonic path). In contrast, no ornithogenic isotopic enrichment was detected in the herbivorous gastropod Margarites helicinus or in SOM from the kelp zone (benthic path). The data are compatible with those obtained from the same location a year before, showing δ15N enrichment in predatory/scavenging hermit crabs Pagurus pubescens below the seabird, and no such changes in kelps Saccharina latissima or their presumed consumers, sea urchins Strongylocentrotus droebachiensis (Zmudczyńska-Skarbek et al., 2015a). The results suggest that, in the conditions of periodic, short-term pulses of ornithogenic nutrient inputs to the local marine environment, which typify the short High Arctic summer, planktonic organisms are the initial organisms to incorporate these nutrients before transfer to the benthic food web via pelagic–benthic coupling. However, the supply of ornithogenic resources alone is insufficient to support benthic producers and the trophic pathways based on them. Overall, the ornithogenic subsidies are not a major nutrient source for marine organisms from below the seabird colony.

Search for the new anti-inflammatory agents based on glycosylated polypeptide complex extracted from sea urchins Strongylocentrotus droebachiensis

We performed the study of the anti-inflammatory activity of glycosylated polypeptide complex (GPC) extracted from sea urchins Strongylocentrotus droebachiensis in the model of acute bronchitis induced by endotracheal administration of 1% formalin solution in male Wistar rats. Animals of experimental groups were inhaled by GPC solution at 25, 50 and 100 mcg/kg, control animals – by the reference drug ambroxol at 3.6 mg/kg once daily during 7 days starting from the day of pathology induction. 24 hours after pathology induction GPC at 100 mcg/kg reduced the total leukocyte count in the bronchoalveolar lavage fluid by 34%, after 48 hours – by 61% compared with control animal group (р ≤ 0.05). If the normal number of goblet cells per 1 mm bronchial mucosa was 33.7 ± 1.7 and after formalin exposure – 67.5 ± 1.8, then after a course administration of polypeptide complex (7 days) at 100 mcg/kg – 55.7 ± 2.7. By the results of morphology and histology study we determined that mononuclear infiltration of bronchial submucosa layer by lymphocytes and macrophages, neutrophil leukocytes of mucosa and submucosa was significantly less than in control animal group (р < 0.05) affected by formalin without any pharmacological protection. Upon the results of the study, we determined the anti-inflammatory activity of glycosylated polypeptide complex at 25, 50 and 100 mcg/kg, which was not inferior to the similar activity of ambroxol (3.6 mg/kg).

Seed Predation by the Shore Crab Carcinus maenas: A Positive Feedback Preventing Eelgrass Recovery?

There is an increasing interest to restore the ecosystem services that eelgrass provides, after their continuous worldwide decline. Most attempts to restore eelgrass using seeds are challenged by very high seed losses and the reasons for these losses are not all clear. We assess the impact of predation on seed loss and eelgrass establishment, and explore methods to decrease seed loss during restoration in the Swedish northwest coast. In a laboratory study we identified three previously undescribed seed predators, the shore crab Carcinus maenas, the hermit crab Pagurus bernhardus and the sea urchin Strongylocentrotus droebachiensis, of which shore crabs consumed 2–7 times more seeds than the other two species. The importance of shore crabs as seed predators was supported in field cage experiments where one enclosed crab caused 73% loss of seeds over a 1-week period on average (~ 21 seeds per day). Seedling establishment was significantly higher (14%) in cages that excluded predators over an 8-month period than in uncaged plots and cages that allowed predators but prevented seed-transport (0.5%), suggesting that seed predation constitutes a major source of seed loss in the study area. Burying the seeds 2 cm below the sediment surface prevented seed predation in the laboratory and decreased predation in the field, constituting a way to decrease seed loss during restoration. Shore crabs may act as a key feedback mechanism that prevent the return of eelgrass both by direct consumption of eelgrass seeds and as a predator of algal mesograzers, allowing algal mats to overgrow eelgrass beds. This shore crab feedback mechanism could become self-generating by promoting the growth of its own nursery habitat (algal mats) and by decreasing the nursery habitat (seagrass meadow) of its dominant predator (cod). This double feedback-loop is supported by a strong increase of shore crab abundance in the last decades and may partly explain the regime shift in vegetation observed along the Swedish west coast.

Small macro‐benthic invertebrates influence the survival, growth and behaviour of juvenile green sea urchins Strongylocentrotus droebachiensis in the laboratory

AbstractRecent settlers of many marine benthic invertebrates are cryptic, which exposes them to a suite of animals that differs from those they may experience as adults, potentially resulting in interactions causing mortality and/or reducing growth. Previous field experiments have indicated that such is the case with small juvenile green sea urchins Strongylocentrotus droebachiensis but which taxa are responsible for the mortality and reduced growth was not determined. A laboratory study was conducted to examine the effects of small macro‐benthic invertebrates, specifically chitons, scaleworms and larger juvenile conspecifics, as well as the full suite of cobble‐dwelling organisms, on the mortality, growth and behaviour of small (<3 mm) juvenile sea urchins. The likelihood of survival of small juvenile sea urchins was lower in the presence of larger juvenile sea urchins or with the full suite of cobble‐dwelling organisms than in the absence of animals. The small juvenile sea urchins survived and grew the best when they were with chitons and scaleworms. The behaviour of small sea urchins with the full suite of cobble‐dwelling organisms was more cryptic than the behaviour of urchins with scaleworms. This study indicates that interactions with the suite of small organisms living amongst cobbles can affect survival, growth and behaviour of small juvenile sea urchins, and that larger juvenile sea urchins can be a source of mortality for smaller conspecifics.

Solar-dried kelp as potential feed in sea urchin aquaculture

Over the past two decades, fishery landings for the highly valued green sea urchin (Strongylocentrotus droebachiensis) have decreased significantly in the Gulf of Maine. Methods for sea urchin aquaculture have been developed in the region, but further growth of the industry is inhibited by the expense of formulated feeds. A potential low-cost solution to this issue is to take advantage of the region’s developing sea vegetable aquaculture industry. A feeding trial was conducted with juvenile hatchery-reared urchins comparing somatic and gonadal growths when fed either fresh wild Saccharina latissima, dried S. latissima, fresh laboratory-reared Porphyra umbilicalis, or the formulated Nofima diet. Somatic and gonadal growths of urchins fed dried S. latissima were intermediate to those fed fresh macroalgae (S. latissima or P. umbilicalis) and the formulated Nofima diet, with significantly faster growth observed in urchins fed the formulated diet and significantly slower growth seen in those fed the fresh macroalgae diets. In light of these results, we propose that dried kelp could suffice as a potential feed in sea urchin aquaculture.

Co-culturing green sea urchins (Strongylocentrotus droebachiensis) with mussels (Mytilus spp.) to control biofouling at an integrated multi-trophic aquaculture site

In a field study, five different stocking densities (i.e. 0, 30, 60, 90, 120ind.net−1 or 0, 2.46, 4.91, 7.37, 9.82ind.m−2) of adult green sea urchins (Strongylocentrotus droebachiensis) were randomly assigned to 30 predator-exclusion nets (i.e. n=6) around cultured mussels (Mytilus spp.) to test the effect of urchin density on biofouling intensity (percent net occlusion) and urchin/mussel growth. After 174days of culture, nets in all treatments containing sea urchins were significantly less fouled than those in the control treatment without urchins. Fouling intensities on nets with the two highest stocking densities of urchins (90 and 120ind.net−1) were approximately 40% less than that on nets with urchins held at the lowest stocking density (30ind.net−1) and 45% less than that on nets without urchins. The differences in fouling intensity among nets with 60, 90, and 120ind.net−1 were not statistically significant. While fouling was significantly reduced in the presence of urchins compared to the control treatment with no urchins, it was not completely eliminated since they were only able to access the inside surface of the nets. Sea urchin somatic and gonad growth declined with increasing stocking density, but there was no significant difference in mussel growth at the different urchin stocking densities. Mussels and sea urchins can be successfully co-cultured with no food input, but there may be a trade-off between the effectiveness of biofouling control and sea urchin growth. Statement of relevanceThis paper examined the use of sea urchins (Strongylocentrotus droebachiensis) to mitigate biofouling in mussel (Mytilus spp.) aquaculture and the effect of sea urchin density on biofouling coverage and mussel growth. Treatments containing sea urchins showed significantly less fouling than a control treatment without urchins. Urchin density had no significant effect on mussel growth.

Novel Antimicrobial Peptides EeCentrocins 1, 2 and EeStrongylocin 2 from the Edible Sea Urchin Echinus esculentus Have 6-Br-Trp Post-Translational Modifications.

The global problem of microbial resistance to antibiotics has resulted in an urgent need to develop new antimicrobial agents. Natural antimicrobial peptides are considered promising candidates for drug development. Echinoderms, which rely on innate immunity factors in the defence against harmful microorganisms, are sources of novel antimicrobial peptides. This study aimed to isolate and characterise antimicrobial peptides from the Edible sea urchin Echinus esculentus. Using bioassay-guided purification and cDNA cloning, three antimicrobial peptides were characterised from the haemocytes of the sea urchin; two heterodimeric peptides and a cysteine-rich peptide. The peptides were named EeCentrocin 1 and 2 and EeStrongylocin 2, respectively, due to their apparent homology to the published centrocins and strongylocins isolated from the green sea urchin Strongylocentrotus droebachiensis. The two centrocin-like peptides EeCentrocin 1 and 2 are intramolecularly connected via a disulphide bond to form a heterodimeric structure, containing a cationic heavy chain of 30 and 32 amino acids and a light chain of 13 amino acids. Additionally, the light chain of EeCentrocin 2 seems to be N-terminally blocked by a pyroglutamic acid residue. The heavy chains of EeCentrocins 1 and 2 were synthesised and shown to be responsible for the antimicrobial activity of the natural peptides. EeStrongylocin 2 contains 6 cysteines engaged in 3 disulphide bonds. A fourth peptide (Ee4635) was also discovered but not fully characterised. Using mass spectrometric and NMR analyses, EeCentrocins 1 and 2, EeStrongylocin 2 and Ee4635 were all shown to contain post-translationally brominated Trp residues in the 6 position of the indole ring.

POPULATION PHARMACOKINETICS OF ENROFLOXACIN AND ITS METABOLITE CIPROFLOXACIN IN THE GREEN SEA URCHIN (STRONGYLOCENTROTUS DROEBACHIENSIS) FOLLOWING INTRACOELOMIC AND IMMERSION ADMINISTRATION.

Sea urchin mass mortality events have been attributed to both infectious and noninfectious etiologies. Bacteria, including Vibrio spp. and Pseudoalteromonas spp., have been isolated during specific mortality events. Aquarium collection sea urchins are also subject to bacterial infections and could benefit from antimicrobial treatment, but pharmacokinetic studies have been lacking for this invertebrate group until recently. This study evaluated the pharmacokinetics of enrofloxacin and its active metabolite ciprofloxacin in the green sea urchin (Strongylocentrotus droebachiensis) after intracoelomic injection and medicated bath immersion administration. The utility of a population pharmacokinetic method using nonlinear mixed effects modeling (NLME) was also evaluated. Thirty sea urchins were assigned to either the injection or immersion group. Twelve study animals and three untreated controls were utilized for each administration method: enrofloxacin 10 mg/kg intracoelomic injection or a 6-hr enrofloxacin 10 mg/L immersion. Each animal was sampled four times from 0 to 120 hr. Water samples were collected during immersion treatment and posttreatment time points in both groups. Hemolymph and water sample drug concentrations were analyzed using high-performance liquid chromatography, and pharmacokinetic parameters were determined using an NLME population pharmacokinetic method. Enrofloxacin concentrations were fit to a two-compartment model with first-order input for the intracoelomic injection group. The enrofloxacin elimination half-life (t½), peak hemolymph concentration (CMAX), and area under the curve (AUC) were 38.82 hr, 90.92 μg/ml, and 1,199 hr·μg/ml, respectively. Enrofloxacin was modeled to a one-compartment model with first-order input for the immersion treatment. The enrofloxacin t½, CMAX, and AUC were 33.46 hr, 0.48 μg/ml, and 32.88 hr·μg/ml, respectively. Ciprofloxacin was detected in trace concentrations in all hemolymph samples, indicating minimal production of this metabolite. The concentrations of enrofloxacin achieved far exceeded minimum inhibitory concentrations reported for teleost pathogens. No adverse effects were associated with enrofloxacin administration by either treatment method or from hemolymph sampling.

Genetic diversity of the NE Atlantic sea urchin Strongylocentrotus droebachiensis unveils chaotic genetic patchiness possibly linked to local selective pressure.

We compared the genetic differentiation in the green sea urchin Strongylocentrotus droebachiensis from discrete populations on the NE Atlantic coast. By using eight recently developed microsatellite markers, genetic structure was compared between populations from the Danish Strait in the south to the Barents Sea in the north (56–79°N). Urchins are spread by pelagic larvae and may be transported long distances by northwards-going ocean currents. Two main superimposed patterns were identified. The first showed a subtle but significant genetic differentiation from the southernmost to the northernmost of the studied populations and could be explained by an isolation by distance model. The second pattern included two coastal populations in mid-Norway (65°N), NH and NS, as well as the northernmost population of continental Norway (71°N) FV. They showed a high degree of differentiation from all other populations. The explanation to the second pattern is most likely chaotic genetic patchiness caused by introgression from another species, S. pallidus, into S. droebachiensis resulting from selective pressure. Ongoing sea urchin collapse and kelp forests recovery are observed in the area of NH, NS and FV populations. High gene flow between populations spanning more than 22° in latitude suggests a high risk of new grazing events to occur rapidly in the future if conditions for sea urchins are favourable. On the other hand, the possibility of hybridization in association with collapsing populations may be used as an early warning indicator for monitoring purposes.Electronic supplementary materialThe online version of this article (doi:10.1007/s00227-015-2801-y) contains supplementary material, which is available to authorized users.