Sea Urchin Echinus Esculentus Research Articles

Hidden cost of pH variability in seagrass beds on marine calcifiers under ocean acidification

Coastal ecosystems experience large environmental variability leading to local adaptation. The key role of variability and adaptation in modulating the biological sensitivity to ocean acidification is increasingly acknowledged. Monitoring and understanding the ecological niche at the right spatio-temporal scale is key to understand the sensitivity of any organism and ecosystems. However, the role of the variability in relevant carbonate chemistry parameters as a driver is often overlooked. For example, the balance between photosynthesis and respiration over the day/night cycle is leading to high pH/pCO2 variability in seagrass beds. We hypothesized that (i) the calcifying larvae of the sea urchin Echinus esculentus exposed to seagrass-driven variability would have some physiological mechanisms to respond to such variability; and (ii) these mechanisms would reach their limit under ocean acidification. We compared the presence and absence of the seagrass Zostera marina in flow through mesocosms fed with seawater with 4 pHs. The carbonate chemistry was monitored and biological response of a sea urchin larvae was documented over 3 weeks. Growth and net calcification rates were measured twice a day to encompass diurnal variability. Our results show that larvae growth rate significantly decreased with decreasing average pHT in both absence and presence of seagrass. Moreover, sea urchin larvae showed a slower growth rate in presence of seagrass, only visible in the lowest pH conditions. In addition, larvae raised in presence of seagrass, maximized calcification during the day, and lower their calcification during the night. In contrast, no significant difference was observed between day and night for the net calcification rate in larvae raised in absence of seagrass. Our results demonstrate the limit of local adaptation to the present range of variability under ocean acidification conditions. It also demonstrates that photosynthetic ecosystems such as seagrass may not play a role of refuge against future ocean acidification.

ECR Spotlight – Nicholas Barrett

ABSTRACT ECR Spotlight is a series of interviews with early-career authors from a selection of papers published in Journal of Experimental Biology and aims to promote not only the diversity of early-career researchers (ECRs) working in experimental biology but also the huge variety of animals and physiological systems that are essential for the ‘comparative’ approach. Nick Barrett is an author on ‘ Behavioural and physiological impacts of low salinity on the sea urchin Echinus esculentus’, published in JEB. Nick is a PhD student in the lab of Professor Lloyd Peck and Professor Elizabeth Harper at British Antarctic Survey, Cambridge, UK, and Department of Earth Sciences, University of Cambridge, UK, investigating the effects of osmotic stress on marine animals, with a focus on the resistance of Antarctic marine species to predicted freshening and lower salinity in the Southern Ocean as a result of climate change.

Behavioural and physiological impacts of low salinity on the sea urchin Echinus esculentus.

Reduced seawater salinity as a result of freshwater input can exert a major influence on the ecophysiology of benthic marine invertebrates, such as echinoderms. While numerous experimental studies have explored the physiological and behavioural effects of short-term, acute exposure to low salinity in echinoids, surprisingly few have investigated the consequences of chronic exposure, or compared the two. In this study, the European sea urchin, Echinus esculentus, was exposed to low salinity over the short term (11‰, 16‰, 21‰, 26‰ and 31‰ for 24 h) and longer term (21, 26 and 31‰ for 25 days). Over the short term, oxygen consumption, activity coefficient and coelomic fluid osmolality were directly correlated with reduced salinity, with 100% survival at ≥21‰ and 0% at ≤16‰. Over the longer term at 21‰ (25 days), oxygen consumption was significantly higher, feeding was significantly reduced and activity coefficient values were significantly lower than at control salinity (31‰). At 26‰, all metrics were comparable to the control by the end of the experiment, suggesting acclimation. Furthermore, beneficial functional resistance (righting ability and metabolic capacity) to acute low salinity was observed at 26‰. Osmolality values were slightly hyperosmotic to the external seawater at all acclimation salinities, while coelomocyte composition and concentration were unaffected by chronic low salinity. Overall, E. esculentus demonstrate phenotypic plasticity that enables acclimation to reduced salinity around 26‰; however, 21‰ represents a lower acclimation threshold, potentially limiting its distribution in coastal areas prone to high freshwater input.

Local flexibility in feeding behaviour and contrasting microhabitat use of an omnivore across latitudes.

As the environment is getting warmer and species are redistributed, consumers can be forced to adjust their interactions with available prey, and this could have cascading effects within food webs. To better understand the capacity for foraging flexibility, our study aimed to determine the diet variability of an ectotherm omnivore inhabiting kelp forests, the sea urchin Echinus esculentus, along its entire latitudinal distribution in the northeast Atlantic. Using a combination of gut content and stable isotope analyses, we determined the diet and trophic position of sea urchins at sites in Portugal (42° N), France (49° N), southern Norway (63° N), and northern Norway (70° N), and related these results to the local abundance and distribution of putative food items. With mean estimated trophic levels ranging from 2.4 to 4.6, omnivory and diet varied substantially within and between sites but not across latitudes. Diet composition generally reflected prey availability within epiphyte or understorey assemblages, with local affinities demonstrating that the sea urchin adjusts its foraging to match the small-scale distribution of food items. A net "preference" for epiphytic food sources was found in northern Norway, where understorey food was limited compared to other regions. We conclude that diet change may occur in response to food source redistribution at multiple spatial scales (microhabitats, sites, regions). Across these scales, the way that key consumers alter their foraging in response to food availability can have important implication for food web dynamics and ecosystem functions along current and future environmental gradients.

Antimicrobial and antibiofilm activity of the EeCentrocin 1 derived peptide EC1-17KV via membrane disruption

BackgroundThe antibiotic resistance and biofilm formation of pathogenic microbes exacerbate the difficulties of anti-infection therapy in the clinic. The structural modification of antimicrobial peptides (AMP) is an effective strategy to develop novel anti-infective agents.MethodSeventeen amino acids (AA) in the longer chain of EeCentrocin 1 (from the edible sea-urchin Echinus esculentus) were truncated and underwent further modification. To produce lead peptides with low toxicity and high efficacy, the antimicrobial activity or cytotoxicity of peptides was evaluated against various multidrug-resistant bacteria/fungi or mammalian cells in vivo/ in vitro. In addition, the stability and modes of action of the lead peptide were investigated.FindingsEC1-17KV displayed potent activity and an expanded antimicrobial spectrum, especially against drug-resistant gram-negative bacteria and fungi, attributable to its enhanced amphiphilicity and net charge. In addition, it exhibits bactericidal/fungicidal activity and effectively increased the animal survival rate and mitigated the histopathological damage induced by multidrug-resistant P. aeruginosa or C. albicans in infected mice or G. mellonella. Moreover, EC1-17KV had a poor ability to induce resistance in bacteria and fungi and exhibited desirable high-salt/high-temperature tolerance properties. In bacteria, EC1-17KV promoted divalent cation release to damage bacterial membrane integrity. In fungi, it changed C. albicans membrane fluidity to increase membrane permeabilization or reduced hyphal formation to suppress biofilm formation.InterpretationEC1-17KV is a promising lead peptide for the development of antimicrobial agents against antibiotic resistant bacteria and fungi.FundingThis work was funded by the National Natural Science Foundation of China (No. 81673483, 81803591); National Science and Technology Major Project Foundation of China (2019ZX09721001-004-005); National Key Research and Development Program of China (2018YFA0902000); "Double First-Class" University project (CPU2018GF/GY16); Natural Science Foundation of Jiangsu Province of China (No. BK20180563); and A Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.

Structure-activity relationship studies of shortened analogues of the antimicrobial peptide EeCentrocin 1 from the sea urchin Echinus esculentus.

EeCentrocin 1 is a potent antimicrobial peptide isolated from the marine sea urchin Echinus esculentus. The peptide has a hetero-dimeric structure with the antimicrobial activity confined in its largest monomer, the heavy chain (HC), encompassing 30 amino acid residues. The aim of the present study was to develop a shorter drug lead peptide using the heavy chain of EeCentrocin 1 as a starting scaffold and to perform a structure-activity relationship study with sequence modifications to optimize antimicrobial activity. The experiments consisted of 1) truncation of the heavy chain, 2) replacement of amino acids unfavourable for in vitro antimicrobial activity, and 3) an alanine scan experiment on the truncated and modified heavy chain sequence to identify essential residues for antimicrobial activity. The heavy chain of EeCentrocin 1 was truncated to less than half its initial size, retaining most of its original antimicrobial activity. The truncated and optimized lead peptide (P6) consisted of the 12 N-terminal amino acid residues from the original EeCentrocin 1 HC sequence and was modified by two amino acid replacements and a C-terminal amidation. Results from the alanine scan indicated that the generated lead peptide (P6) contained the optimal sequence for antibacterial activity, in which none of the alanine scan peptides could surpass its antimicrobial activity. The lead peptide (P6) was also superior in antifungal activity compared to the other peptides prepared and showed minimal inhibitory concentrations (MICs) in the low micromolar range. In addition, the lead peptide (P6) displayed minor haemolytic and no cytotoxic activity, making it a promising lead for further antimicrobial drug development.

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.

NGFFFamide and echinotocin: structurally unrelated myoactive neuropeptides derived from neurophysin-containing precursors in sea urchins

The myoactive neuropeptide NGIWYamide was originally isolated from the holothurian (sea cucumber) Apostichopus japonicus but there is evidence that NGIWYamide-like peptides also occur in other echinoderms. Here we report the discovery of a gene in the sea urchin Strongylocentrotus purpuratus that encodes two copies of an NGIWYamide-like peptide: Asn-Gly-Phe-Phe-Phe-(NH(2)) or NGFFFamide. Interestingly, the C-terminal region of the NGFFFamide precursor shares sequence similarity with neurophysins, carrier proteins hitherto uniquely associated with precursors of vasopressin/oxytocin-like neuropeptides. Thus, the NGFFFamide precursor is the first neurophysin-containing neuropeptide precursor to be discovered that does not contain a vasopressin/oxytocin-like peptide. However, it remains to be determined whether neurophysin acts as a carrier protein for NGFFFamide. The S. purpuratus genome also contains a gene encoding a precursor comprising a neurophysin polypeptide and 'echinotocin' (CFISNCPKGamide) - the first vasopressin/oxytocin-like peptide to be identified in an echinoderm. Therefore, in S. purpuratus there are two genes encoding precursors that have a neurophysin domain but which encode neuropeptides that are structurally unrelated. Furthermore, both NGFFFamide and echinotocin cause contraction of tube foot and oesophagus preparations from the sea urchin Echinus esculentus, consistent with the myoactivity of NGIWYamide in sea cucumbers and the myoactivity of vasopressin/oxytocin-like peptides in other animal phyla. Presumably the NGFFFamide precursor acquired its neurophysin domain following partial or complete duplication of a gene encoding a vasopressin/oxytocin-like peptide, but it remains to be determined when in evolutionary history this occurred.

Molecular characterisation of SALMFamide neuropeptides in sea urchins

The SALMFamides are a family of neuropeptides found in species belonging to the phylum Echinodermata. Members of this family have been identified in starfish (class Asteroidea) and in sea cucumbers (class Holothuroidea) but not in other echinoderms. Our aim here was to characterise SALMFamide neuropeptides in sea urchins (class Echinoidea). Radioimmunoassays for the starfish SALMFamides S1 and S2 were used to test for related peptides in whole-body acetone extracts of the sea urchin Echinus esculentus. Fractionation of extracts using high performance liquid chromatography (HPLC) revealed several peaks of SALMFamide-like immunoreactivity, with two S2-like immunoreactive peaks (3 and 4) being the most prominent. However, peak 4 could not be purified to homogeneity and although peak 3 was purified, only a partial sequence (MRYH) could be obtained. An alternative strategy for identification of echinoid SALMFamides was provided by sequencing the genome of the sea urchin Strongylocentrotus purpuratus. Analysis of whole-genome shotgun sequence data using the Basic Local Alignment Search Tool (BLAST) identified a contig (347664) that contains a coding region for seven putative SALMFamide neuropeptides (PPVTTRSKFTFamide, DAYSAFSFamide, GMSAFSFamide, AQPSFAFamide, GLMPSFAFamide, PHGGSAFVFamide and GDLAFAFamide), which we have named SpurS1-SpurS7, respectively. Three of these peptides (SpurS1-3) have the C-terminal sequences TFamide or SFamide, which are identical or similar to the C-terminal region of the starfish SALMFamide S2. This may explain the occurrence of several S2-like immunoreactive peptides in extracts of Echinus esculentus. Detailed analysis of the sequence of contig 347664 indicated that the SALMFamide gene in Strongylocentrotus purpuratus comprises two exons, with the first exon encoding a signal peptide sequence and the second exon encoding SpurS1-SpurS7. Characterisation of this gene is important because it is the first echinoderm neuropeptide precursor sequence to be identified and, more specifically, it provides our first insight into the structure and organisation of a SALMFamide gene in an echinoderm. In particular, it has revealed a hitherto unknown complexity in the diversity of SALMFamide neuropeptides that may occur in an echinoderm species because all previous studies, which relied on peptide purification and sequencing, revealed only two SALMFamide neuropeptides in each species examined. It now remains to be established whether or not the occurrence of more than two SALMFamides in Strongylocentrotus purpuratus is a feature that is peculiar to this species and to echinoids in general or is more widespread across the phylum Echinodermata. Identification of SpurS1-SpurS7 provides the basis for comparative analysis of the physiological actions of these peptides in sea urchins and for exploitation of the sea urchin genome sequence to identify the receptor(s) that mediate effects of SALMFamides in echinoderms.

The effect of diet type and quantity on the development of common sea urchin larvae Echinus esculentus

Several species of sea urchins are now being cultivated for commercial purposes and with the continued increased demand for sea urchin gonads as a food product, new species are being assessed for their aquaculture and market potential. This study focussed on establishing protocols for the production of common sea urchin Echinus esculentus larvae and juveniles to assess its potential as an echinoculture species. Two trials were carried out, the first trial evaluated the influence of three microalgal diets (D= Dunaliella tertiolecta only, mixed D/P= D. tertiolecta plus Phaeodactylum tricornutum and P= P. tricornutum only) on larval morphology. Larval length, width, post-oral arm length and rudiment length were significantly effected by diet. Diets D and D/P prompted more rapid metamorphosis. In the second trial, the effects of different rations of D. tertiolecta were tested. The food ration, standard ration (SR; 1000, 3000, and 5000 cells ml −1 ) and high ration (HR; 3000, 9000, and 15,000 cells ml −1 ) were increased as the larvae acquired the 3rd and 4th pair of larval arms. Larvae fed the SR were significantly larger (longer and wider) and had significantly longer rudiments than those in the HR treatment. The number of larvae metamorphosing and settling onto substrates was significantly higher in treatment SR compared to HR. Optimising the larval diet shortened the larval stage from 21–23 days in the first trial to 16 days in the second trial. The maximum percentage of metamorphosing individuals which survived to post-larvae or juveniles (10 days after they were first judged competent to settle) was 46.6%, suggesting E. esculentus is a viable aquaculture candidate.

Nutritive value of protein from sea urchin, and its effects on intestinal leucine aminopeptidase and intestinal and hepatic gamma-glutamyltranspeptidase

Seafoods are a rich source of easily digestible protein that also provides polyunsaturated fatty acids, vitamins and minerals for human nutrition. The purpose of this study was to determine the nutritive value of diets high in protein from two species of sea urchin (Paracentrotus lividus and Echinus esculentus) as compared to a high-quality reference protein such as casein, as well as the effects of these diets on leucine aminopeptidase and gamma-glutamyltranspeptidase, intestinal and hepatic enzymes. The test was carried out on three groups of male rats fed these diets for 23 days. The result of the nutritive parameters indicated that sea urchin, Echinus esculentus, were significantly lower than the casein protein except for food intake, and the nutritive parameters of sea urchin, Paracentrotus lividus, were similar to the values obtained for casein protein except for digestibility and net protein utilization. Intestinal leucine aminopeptidase activity was significantly lower (P < 0.05) in the group fed Paracentrotus lividus as compared to the group fed casein. Intestinal gamma-glutamyltranspeptidase showed a significantly higher activity in the group fed E. esculentus than in the two other groups and the hepatic gamma-glutamyltranspeptidase activity in the groups fed the two species of sea urchin were lower. Nutritive values suggested that these marine species are a good protein source and similar to casein. The activity of the enzymes under study must have been affected by the amino acid composition of the protein.

The macrofauna of a stony sand area in the German Bight (North Sea)

The sublittoral macrofauna of the Steingrund, a stony area east-northeast of Helgoland, was investigated from May till October 1991 using a van Veen grab and a small dredge. The diverse endo- and epifauna of the sandy bottoms, pebbles and boulders of this Saalian end moraine comprised 289 taxa, whereby the polychaetesMagelona papillicornis, Lanice conchilega andSpiophanes bombyx dominated in terms of abundance. Species rare in the German Bight, such as the spongeLeucandra fistulosa, the sea urchinEchinus esculentus, and the sea anemoneHaliplanella lineata, were also found. The two sample sets were processed separately with multivariate techniques, and differentiated on the basis of occurrence and numbers of the abundant species. The analysis of the grab samples revealed two types of theTellina-fabula-community. These associations were differentiated by the presence of species of the coarse-sand-inhabitingGoniadella-Spisula-community and were related to the distribution of the grain size of the sediment. Likewise, two epifaunal assemblages were distinguished. Sandy bottoms were characterized byOphiura albida, Liocarcinus holsatus andPagurus bernhardus, while boulders and pebbles were covered by a varied sessile and mobile epifauna dominated by the sessile bryozoanFlustra foliacea and the mobile pantopodeAechelia echinata. Numerical density, biomass and annual production estimates are in the range of values determined for the macrobenthos of the German Bight, while annual P/B ratios mounted up to 5.

Natural growth bands and growth variability in the sea urchin Echinus esculentus: results from tetracycline tagging

Growth of the European edible sea urchin Echinus esculentus L. was studied in a population held for 2 yr in cages on the sea bed, after labelling with the skeletal growth marker tetracycline. The final position of the tetracycline tag on the genital plates agreed with an annual periodicity in natural growth zones; two such growth zones appeared beyond the position of the tag on the ground surface of the plate as light-reflecting bands separated by narrow dark lines in the middle layer. Individual and group (pooled data) growth parameters were estimated from the growth increment shown in the genital plate, whose lateral growth displayed a linear relationship to the diameter of the urchin test within the size range of these measurements. Von Bertalanffy growth parameters (asymptotic size and growth-rate function K) fitted to the growth increment on each individual were highly significantly correlated to those fitted to the natural growth lines, assuming an annual periodicity. The inferred growth pattern agrees well with conclusions based on H. B. Moore's growth-band data. The caged urchins can be assumed to have experienced exactly similar conditions, yet the growth curves fitted to individuals showed considerable variability. The good agreement between estimated growth function parameters of individuals obtained by the two methods indicate that this reflects real variability in growth between individuals that probably is genetically rather than environmentally determined. The growth of E. esculentus, and the adaptational significance of high growth variability in the population is briefly discussed.

Growth Bands in the sea Urchin Echinus Esculentus: Results from Tetracycline-Mark/Recapture

Recoveries of tetracycline-labelled specimens of the sea urchin Echinus esculentus (Echinodermata: Echinoidea) from a wild population marked two years previously indicate very low skeletal growth rates in large adults. The post-tag growth in the test of a smaller specimen showed two clear growth zones in the middle layer of the plates, this conforming to the expectation of a single growth band each year. Merging of the spinochrome pigment bands present in the outer layer near the plate edge in older urchins will probably result in underestimation of age based on counts of these bands.The large literature on growth banding in the European sea urchin Echinus esculentus L. and other echinoids is reviewed by Pearse &amp; Pearse (1975), Smith (1980) and Gage (1991). Moore (1935) utilised spinochrome pigment banding in the genital (apical) plates of E. esculentus from the Isle of Man (Irish Sea) and Firth of Clyde (western Scotland) in one of the first studies utilising growth bands to interpret the age structure and growth rates of sea urchins. A single band was assumed to be formed each year. Counts of spinochrome bands have been used to obtain nearly all subsequently published age data for this species (Sime, 1982; Nichols et al., 1985; Sime &amp; Cranmer, 1985; Comely &amp; Ansell, 1988).The present study was aimed at helping to resolve differing interpretations of age and growth rates in Echinus esculentus provided by these studies. This was undertaken by time marking the skeletal plates of a large sample of a wild population accessible by scuba diving on a submerged rock reef at 10–15 m depth off the islet of Eilean Mor near the Dunstaffnage Laboratory.

Growth in populations of the sea-urchin EchinusEsculentus L. (Echinodermata : Echinoidea) from the English Channel and Firth of Clyde

Growth and rate of growth curves, computed by the single logistic model, are given for populations of Echinus esculentus L. from sites near Plymouth, in the English Channel, and at Great Cumbrae, Firth of Clyde. The growth curves show a sigmoid shape, with their origins corresponding well with directly-read diameters of recently-metamorphosed juveniles, and the upper asymptote, approaching 14 cm horizontal diameter for Plymouth and 12 cm for Cumbrae, corresponding with ages of 8–12 yr and 8–10 yr, respectively. The gonopores open, and the gonads become functional, at between 0.94 and 1.66 cm ambital diameter, corresponding to an age of 1.5 to 2.5 yr. Maximum rate of growth in the Plymouth region was at mean age 4.7 yr, and at Cumbrae 4.3 yr. Results for Cumbrae are compared with those obtained there on the same species by two previous workers.

Bactericidal Activity of Coelomic Fluid of the Sea Urchin, Echinus Esculentus, on Different Marine Bacteria

Coelomic fluid from the edible sea urchin Echinus esculentus (L.) has in vitro bactericidal activity against the marine pseudomonad, designated strain No. 111 (Wardlaw &amp; Unkles, 1978). This particular bacterial strain was chosen because of its highly characteristic jet-black, agar-digesting colonies on marine agar plates which permitted it to be easily distinguishable from contaminants in bactericidal tests. Bactericidal activity is localised in the cellular components of the coelomic fluid, particularly in the red spherule cells (Messer &amp; Wardlaw, 1980) and is demonstrable in almost all animals tested.

The innervation of spines in the sea-urchin Echinus esculentus L.

The fine structure of the soft tissues at the bases of spines in the sea-urchin Echinus esculentus has been examined with particular reference to the innervation of these appendages. The basal nerve ring encircling the spine contains many somata of neurones, and circumferentially directed elements, as well as tangled neuropil. The smooth muscles that bring about spine-pointing movements are innervated by terminals that contain two different types of vesicles, suggesting dual innervation by neurones containing different neurotransmitters. The neuromuscular junctions include apparent synapses between nerve cell bodies and muscle fibres. There are also neural elements that may be involved in the control of the catch apparatus of the spine. The complexity of the nerve ring and effector innervation implies that coordination of spine movements is more sophisticated than has been previously supposed.

Echinochrome-A as a bactericidal substance in the coelomic fluid of Echinus esculentus (L.)

1. 1. The concentrations of echinochrome-A in coelomic fluid from healthy specimens of the sea urchin Echinus esculentus (L.) ranged from 3 to 60 μg/ml, with a geometric mean of 14 μg/ml. 2. 2. Echinochrome-A (50 μg/ml) dissolved in sea water, with the aid of mammalian proteins as dispersants, was bactericidal or bacteriostatic towards six out of seven strains of marine gram-negative and gram-positive bacteria. 3. 3. Echinochrome-A is suggested as a major factor in the bactericidal activity of coelomic fluid from E. esculentus.

Shallow sublittoral ecosystems in the Inner Hebrides

SynopsisRapid advances in scientific SCUBA diving have provided a means of investigating the previously difficult ground of the shallow sublittoral. Dhing surveys of the Inner Hebridean islands have been promoted and coordinated by the Nature Conservancy Council (NCC) and the Underwater Conservation Society (UCS) to provide appropriate data for reviewing the marine nature conservation importance of the area. Although the surveys have been extensive rather than intensive, and many areas have yet to be investigated, a short preliminary descriptive account of the communities of the shallow seas of the Inner Hebrides is presented in this paper.The classification and description of sublittoral habitats is essentially related to the substratum type and the influence of water movement and light penetration. Although the diversity of habitat types is probably less for the Inner Hebrides than either the outer islands or the mainland, the larger islands show a range of exposure from the sheltered mud of sea lochs to wave- and tide-exposed bedrock. The juxtaposition of three marine biogeographical regions around the British Isles is reflected in the biota of the Inner Hebrides. In addition to the typical ‘Scottish’ sublittoral biota there is an associated assemblage of south-western species, and a number of northern species at their south-western limit. In many areas the diversity of the biota is reduced by the intense grazing of the sea urchin Echinus esculentus, a notably Scottish phenomenon.

Papers from the Echinoderm Conference. 9. A biometrical study of populations of the European sea-urchin Echinus esculentus (Echinodermata: Echinoidea) from four areas of the British Isles

Results submitted by mainly amateur diving groups during Underwater Conservation Year 1977 in the United Kingdom show that there are regional differences in the relationship between both size and shape of specimens of the European sea-urchin Echinus esculentus Linnaeus and the depth at which they occur. Populations from South-West England are significantly bigger at all depths than those from the other areas surveyed, those from Western Scotland increase in size more rapidly with increasing depth of water, and those from the North Sea decrease in size with increasing depth. Two sites surveyed in South-West Ireland show that exposure may affect the size of urchins inhabiting shallow waters. The results are compared with those of a similar survey by Larsson (1968) on the same species in Swedish waters.