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Sea anemones are valuable for therapeutic research as a diversified source of bioactive molecules, due to their diverse bioactive molecules linked to predation and defence mechanisms involving toxins and antimicrobial peptides. Acid extracts from Actinia equina tentacles and body were examined for antibacterial activity against Gram-positive, Gram-negative bacteria, and fungi. The peptide fractions showed interesting minimum inhibitory concentration (MIC) values (up to 0.125 µg/mL) against the tested pathogens. Further investigation and characterization of tentacle acid extracts with significant antimicrobial activity led to the purification of peptides through reverse phase chromatography on solid phase and HPLC. Broad-spectrum antimicrobial peptide activity was found in 40% acetonitrile fractions. The resulting peptides had a molecular mass of 2612.91 and 3934.827 Da and MIC ranging from 0.06 to 0.20 mg/mL. Sequencing revealed similarities to AMPs found in amphibians, fish, and Cnidaria, with anti-Gram+, Gram-, antifungal, candidacidal, anti-methicillin-resistant Staphylococcus aureus, carbapenemase-producing, vancomycin-resistant bacteria, and multi-drug resistant activity. Peptides 6.2 and 7.3, named Equinin A and B, respectively, were synthesized and evaluated in vitro towards the above-mentioned bacterial pathogens. Equinin B exerted interesting antibacterial activity (MIC and bactericidal concentrations of 1 mg/mL and 0.25 mg/mL, respectively) and gene organization supporting its potential in applied research. [ABSTRACT FROM AUTHOR]

Sea anemones are valuable for therapeutic research as a diversified source of bioactive molecules, due to their diverse bioactive molecules linked to predation and defence mechanisms involving toxins and antimicrobial peptides. Acid extracts from Actinia equina tentacles and body were examined for antibacterial activity against Gram-positive, Gram-negative bacteria, and fungi. The peptide fractions showed interesting minimum inhibitory concentration (MIC) values (up to 0.125 µg/mL) against the tested pathogens. Further investigation and characterization of tentacle acid extracts with significant antimicrobial activity led to the purification of peptides through reverse phase chromatography on solid phase and HPLC. Broad-spectrum antimicrobial peptide activity was found in 40% acetonitrile fractions. The resulting peptides had a molecular mass of 2612.91 and 3934.827 Da and MIC ranging from 0.06 to 0.20 mg/mL. Sequencing revealed similarities to AMPs found in amphibians, fish, and Cnidaria, with anti-Gram+, Gram-, antifungal, candidacidal, anti-methicillin-resistant Staphylococcus aureus, carbapenemase-producing, vancomycin-resistant bacteria, and multi-drug resistant activity. Peptides 6.2 and 7.3, named Equinin A and B, respectively, were synthesized and evaluated in vitro towards the above-mentioned bacterial pathogens. Equinin B exerted interesting antibacterial activity (MIC and bactericidal concentrations of 1 mg/mL and 0.25 mg/mL, respectively) and gene organization supporting its potential in applied research.

Global warming and connected acidification of the world ocean attract a substantial amount of research efforts, in particular in a context of their impact on behaviour and metabolism of marine organisms, such as Cnidaria. Nevertheless, mechanisms underlying Cnidarians' neural signalling and behaviour and their (possible) alterations due to the world ocean acidification remain poorly understood. Here we researched for the first time modulation of GABAA receptors (GABAARs) in Actinia equina (Cnidaria: Anthozoa) by pH fluctuations within a range predicted by the world ocean acidification scenarios for the next 80–100 years and by selective pharmacological activation. We found that in line with earlier studies on vertebrates, both changes of pH and activation of GABAARs with a selective allosteric agonist (diazepam) modulate electrical charge transfer through GABAAR and the whole-cell excitability. On top of that, diazepam modifies the animal behavioural reaction on startle response. However, despite behavioural reactions displayed by living animals are controlled by GABAARs, changes of pH do not alter them significantly. Possible mechanisms underlying the species resistance to acidification impact are discussed. [ABSTRACT FROM AUTHOR]

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Theoretical models of animal contests such as the Hawk-Dove game predict that variation in fighting behavior will persist due to mixed evolutionarily stable strategies (ESS) under certain conditions. However, the genetic basis for this variation is poorly understood and a mixed ESS for fighting can be interpreted in more than one way. Specifically, we do not know whether variation in aggression within a population arises from among-individual differences in fixed strategy (determined by an individual's genotype—direct genetic effects [DGEs]), or from within-individual variation in strategy across contests. Furthermore, as suggested by developments of the original Hawk-Dove model, within-individual variation in strategy may be dependent on the phenotype and thus genotype of the opponent (indirect genetic effects—IGEs). Here we test for the effect of DGEs and IGEs during fights in the beadlet sea anemone Actinia equina. By exploiting the unusual reproductive system of sea anemones, combined with new molecular data, we investigate the role of both additive (DGE + IGE) and non-additive (DGE × IGE) genetic effects on fighting parameters, the latter of which have been hypothesized but never tested for explicitly. We find evidence for heritable variation in fighting ability and that fight duration increases with relatedness. Fighting success is influenced additively by DGEs and IGEs but we found no evidence for non-additive IGEs. These results indicate that variation in fighting behavior is driven by additive indirect genetic effects (DGE + IGE), and support a core assumption of contest theory that strategies are fixed by DGEs. [ABSTRACT FROM AUTHOR]

Abstract Anemones of the genus Actinia are ecologically important and familiar organisms on many rocky shores. However, this genus is taxonomically problematical and prior evidence suggests that the North Atlantic beadlet anemone, Actinia equina , may actually consist of a number of cryptic species. Previous genetic work has been largely limited to allozyme electrophoresis and there remains a dearth of genetic resources with which to study this genus. Mitochondrial DNA sequencing may help to clarify the taxonomy of Actinia. Here, the complete mitochondrial genome of the beadlet anemone Actinia equina (Cnidaria: Anthozoa: Actinaria: Actiniidae) is shown to be 20,690 bp in length and to contain the standard complement of Cnidarian features including 13 protein coding genes, two rRNA genes, two tRNAs and two Group I introns, one with an in-frame truncated homing endonuclease gene open reading frame. However, amplification and sequencing of the standard mtDNA barcoding region of the cytochrome oxidase I gene revealed only two haplotypes, differing by a single base pair, in widely geographically separated A. equina and its congener A. prasina. COI barcoding shows that whilst A. equina and A. prasina share the common mtDNA haplotype, haplotype frequency differed significantly between A. equina with red/orange pedal discs and those with green pedal discs, consistent with the hypothesis that these morphotypes represent incipient species. Highlights • The complete mitochondrial genome of the anemone Actinia equina is deduced. • Variability in the barcoding gene COI is low with just two haplotypes detected. • The frequency of haplotypes differs significantly between colour morphs. [ABSTRACT FROM AUTHOR]

The diversification of anthozoan toxins played an important role in the ability to colonize various ecological niches. In this study we evaluated the hemolytic activity of HPLC separated fraction of tentacle extracts of sea anemone Actinia equina. Toxic components from acid tissue tentacle extracts were investigated by size exclusion and reverse phase HPLC to characterize cytolytic molecules. A novel low molecular weight active fraction was sequenced by MALDI TOF analysis and a protein correspondent to 5.4 kDa Sodium channel neurotoxin (Ae1) from A. equina was identified. Synthetic Ae1 was assayed and it showed an hemolytic activity against mammalian erythrocytes in a dose dependent manner. Cytolytic activity in addition to neuro-inhibitory function could be a further property of Ae1 toxin repertoire.

Marine species represent a great source of biologically active substances; Actinia equina (AE), an Anthozoa Cnidaria belonging to the Actinidiae family, have been proposed as original food and have already been included in several cooking recipes in local Mediterranean shores, and endowed with excellent nutraceutical potential. The aim of this study was to investigate some unexplored features of AE, through analytical screening and an in-vitro and in-vivo model. An in-vitro study, made on RAW 264.7 stimulated with H2O2, showed that the pre-treatment with AE exerted an antioxidant action, reducing lipid peroxidation and up-regulating antioxidant enzymes. On the other hand, the in-vivo study over murine model demonstrated that the administration of AE extracts is able to reduce the carrageenan (CAR)-induced paw edema. Furthermore, the histological damage due to the neutrophil infiltration is prevented, and this highlights precious anti-inflammatory features of the interesting food-stuff. Moreover, it was assessed that AE extract modulated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) and The nuclear factor erythroid 2–related factor 2 (Nrf-2) pathways. In conclusion, our data demonstrated that thanks to the antioxidant and anti-inflammatory properties, AE extract could be used as a new food supplement for inflammatory pathology prevention.

The mucus produced by many marine organisms is a complex mixture of proteins and polysaccharides forming a weak watery gel. It is essential for vital processes including locomotion, navigation, structural support, heterotrophic feeding and defence against a multitude of environmental stresses, predators, parasites, and pathogens. In the present study we focused on mucus produced by a benthic cnidarian, the sea anemone Actinia equina (Linnaeus, 1758) for preventing burial by excess sedimentation and for protection. We investigated some of the physico-chemical properties of this matrix such as viscosity, osmolarity, electrical conductivity, protein, carbohydrate, and total lipid contents. Some biological activities such as hemolytic, cytotoxic, and antibacterial lysozyme-like activities were also studied. The A. equina mucus is mainly composed by water (96.2% ± 0.3%), whereas its dry weight is made of 24.2% ± 1.3% proteins and 7.8% ± 0.2% carbohydrates, with the smallest and largest components referable to lipids (0.9%) and inorganic matter (67.1%). The A. equina mucus matrix exhibited hemolytic activity on rabbit erythrocytes, cytotoxic activity against the tumor cell line K562 (human erythromyeloblastoid leukemia) and antibacterial lysozyme-like activity. The findings from this study improve the available information on the mucus composition in invertebrates and have implications for future investigations related to exploitation of A. equina and other sea anemones’ mucus as a source of bioactive compounds of high pharmaceutical and biotechnological interest.

An individual's performance during a fight is influenced by a combination of their capacity and willingness to compete. While willingness to fight is known to be determined by both intrinsic and extrinsic drivers, an individual's capacity to fight is generally thought of as solely intrinsic, being driven by a host of physiological factors. However, evidence indicates that variation in fighting ability can also be generated through exposure to different environmental conditions. Environmental contributions to fighting ability may be particularly important for animals living in spatially and temporally heterogeneous habitats, in which fights can occur between rivals recently exposed to different environmental conditions. The rapidly changing environment experienced within intertidal zones, for example, means that seawater parameters, including dissolved oxygen content and temperature, can vary across small spatial and temporal scales. Here, we investigated the relative importance of these extrinsic contributions to fighting ability and resource value on contest dynamics in the beadlet sea anemone Actinia equina. We manipulated the extrinsic fighting ability of both opponents (through dissolved oxygen concentration prior to fights) and resource value (through seawater flow rate during the fight). Our results indicate that the extrinsic fighting ability of both opponents can interact with resource value to drive escalation patterns and that extrinsic drivers can be more important in determining contest dynamics than the intrinsic traits commonly studied. Our study highlights the need to combine data on intrinsic state and extrinsic conditions in order to gain a more holistic view of the factors driving contest behaviour. [ABSTRACT FROM AUTHOR]

Abstract We examined the gene expression levels of equinatoxin and equistatin in the sea anemone Actinia equina, when reared at varying environmental temperatures for five months. Both genes were significantly downregulated at 10 °C compared to 16 °C but showed no significant change at 22 °C. This provides the first evidence of an effect of temperature on gene expression, but with no effect of increasing temperatures such as those predicted due to climate change. Highlights • Our results indicate environmental temperature significantly influences the expression of two genes within Actinia equina. • Equinatoxin and equistatin are both downregulated when acclimatised from 16 to 10 °C. • There is no set relationship between toxin gene expression and temperature, the effect is gene specific. [ABSTRACT FROM AUTHOR]

The ability to mitigate the costs of engaging in a fight will depend on an individual's physiological state. However, the experience of fighting itself may, in turn, affect an individual's state, especially if the fight results in injury. Previous studies have found a correlation between immune state and fighting success, but the causal direction of this relationship remains unclear. Does immune state determine fighting success? Or does fighting itself influence subsequent immune state? Using the beadlet anemone, Actinia equina, we disentangled the cause and effect of this relationship, measuring immune response once pre-fight and twice post-fight. Contrary to previous findings, pre-fight immune response did not predict fighting success, but rather predicted whether an individual used its weapons during the fight. Furthermore, weapon use and contest outcome significantly affected post-fight immune response. Individuals that used their weapons maintained a stable immune response following the fight, whereas those that fought non-injuriously did not. Furthermore, although winners suffered a reduction in immune response similar to that of losers immediately postfight, winners began to recover pre-fight levels within 24 h. Our findings indicate that immune state can influence strategic fighting decisions and, moreover, that fight outcome and the agonistic behaviours expressed can significantly affect subsequent immunity. [ABSTRACT FROM AUTHOR]

Anemones exhibit distinct between-individual differences in behaviours such as risk-taking and aggressiveness. The genus of anemone Actinia contains numerous morphotypes which occupy different locations on the shore and show different levels of aggressiveness. In this study we explored whether their propensity to take risks likewise differed between three groups of anemones: Actinia prasina ; a low shore morph of Actinia equina characterised by a blue limbus around the pedal disc (described as ring-present, RP); and upper shore morphs of A. equina characterised by a lack of such a ring (ring-absent, RA). Risk-taking behaviour was measured using startle-response durations across two trials, separated by two weeks. In-between trials anemones were allowed to engage in pairwise contests with a randomly-selected opponent, during which the number of occurrences of behaviours related to movement of the body, tentacles and acrorhagi were counted and compared between groups to identify systematic variation in potentially offensive and defensive postures. Length of holotrich nematocysts, thought to be linked to aggressiveness, was also measured. Both risk-taking and inflation/deflation of acrorhagi significantly differed between groups: RA anemones were risk-prone and aggressive, RP anemones risk-averse and non-aggressive, A. prasina occupying a position in-between. Likewise nematocyst lengths varied between groups, shortest among RP anemones and longest in RA anemones. These data suggest that different morphotypes are associated with differences in risk-taking which may result from a complex interplay of various ecological factors linked to the habitats these morphotypes occupy, and add further credence to theories on speciation within the Actinia equina species complex. [ABSTRACT FROM AUTHOR]

Fighting experience (specifically winning or losing a fight) can significantly alter boldness, a component of resource-holding potential (RHP). Previous studies have shown that both the repeatability of boldness and mean-level boldness can be affected by fighting experience and that these effects are strongest in the recipients of agonistic behaviour. However, whether these postfight changes in boldness impact future contest success and whether subsequent contests further affect boldness remain unknown. Furthermore, little is known about the effects of the specific tactics used within a fight (within-fight experience) and how these might influence future fight performance and boldness. Here, we investigated the relationship between fighting success and boldness (measured as recovery time when startled) across repeated contests in the beadlet sea anemone, Actinia equina , measuring boldness on five occasions before, between and after two contests. We found that boldness (both repeatability and mean-level) was generally robust to the effects of fighting experience, apart from a decrease in the immediate boldness of losers after their second fight. Furthermore, we found that while prefight boldness significantly predicted fighting success and the level of aggression used in an individual's first fight, it did not predict victory or aggression in the second fight. Our findings thus indicate that different traits may be important in determining fighting success in consecutive fights and, moreover, that fighting experience may alter which traits contribute to an individual's RHP. [ABSTRACT FROM AUTHOR]

Marine invertebrates have been attracting the attention of researchers for their application in nutrition, agriculture, and the pharmaceutical industry, among others. Concerning sea anemones (Cnidaria), little is known regarding their metabolic profiles and potential value as a source of pharmacologically-active agents. In this work, the chemical profiles of two species of sea anemones Actinia equina and Anemonia sulcata, were studied by high-performance liquid chromatography with diode-array detection (HPLC-DAD) and its impact upon immune and gastric cells was evaluated. In both species, the methylpyridinium alkaloid homarine was the major compound in aqueous extracts. The extracts were effective in reducing lipopolysaccharide (LPS)-induced levels of nitric oxide (NO) and intracellular reactive oxygen species (ROS) in a macrophage model of inflammation. Both the extracts and the alkaloid homarine were effective in inhibiting phospholipase A2 (PLA2), a pivotal enzyme in the initial steps of the inflammatory cascade. In order to mimic the oral consumption of these extracts; their effect upon human gastric cells was evaluated. While no caspase-9 activation was detected, the fact that the endoplasmic reticulum-resident caspase-4, and also caspase-3, were activated points to a non-classical mechanism of apoptosis in human gastric cells. This work provides new insights on the toxicity and biological potential of sea anemones increasingly present in human nutrition. [ABSTRACT FROM AUTHOR]

Animal personality studies rely on collecting repeated behavioural data either in the field or under laboratory conditions. Conditions in the field should be far less stable than controlled laboratory conditions, and hence represent a potential source of variation in behaviour. Here we report on the first experiment to our knowledge that formally compares the repeatability of identical behaviours in the laboratory and the field, and across the transition from laboratory to field. Using a design that controls for observation number we compared two groups of sea anemones, observed across two experimental phases, either (1) in the field followed by the laboratory or (2) in the laboratory only. We analysed differences in behaviour across a range of levels including repeatability and its between- and within-individual variance components. Although mean startle response durations varied between the laboratory and field, there was no significant difference in repeatability across situations. Within-individual variance differed between the two periods of the experiment for animals observed only in the laboratory but this effect was not present for those that transitioned from field to laboratory. Furthermore, the rank order of individual responses was stable for animals observed only in the laboratory but changed for those that transitioned from field to laboratory. These results show that although repeatability estimates in the laboratory can yield results like those obtained in the field, the underlying components of consistent variation in behaviour might be influenced by an interaction between prior experiences and the current situation in which the animals are observed. [ABSTRACT FROM AUTHOR]

The diversification of anthozoan toxins played an important role in the ability to colonize various ecological niches. In this study we evaluated the hemolytic activity of HPLC separated fraction of tentacle extracts of sea anemone Actinia equina. Toxic components from acid tissue tentacle extracts were investigated by size exclusion and reverse phase HPLC to characterize cytolytic molecules. A novel low molecular weight active fraction was sequenced by MALDI TOF analysis and a protein correspondent to 5.4 kDa Sodium channel neurotoxin (Ae1) from A. equina was identified. Synthetic Ae1 was assayed and it showed an hemolytic activity against mammalian erythrocytes in a dose dependent manner. Cytolytic activity in addition to neuro-inhibitory function could be a further property of Ae1 toxin repertoire.

The diversification of anthozoan toxins played an important role in the ability to colonize various ecological niches. In this study we evaluated the hemolytic activity of HPLC separated fraction of tentacle extracts of sea anemone Actinia equina. Toxic components from acid tissue tentacle extracts were investigated by size exclusion and reverse phase HPLC to characterize cytolytic molecules. A novel low molecular weight active fraction was sequenced by MALDI TOF analysis and a protein correspondent to 5.4 kDa Sodium channel neurotoxin (Ae1) from A. equina was identified. Synthetic Ae1 was assayed and it showed an hemolytic activity against mammalian erythrocytes in a dose dependent manner. Cytolytic activity in addition to neuro-inhibitory function could be a further property of Ae1 toxin repertoire. [ABSTRACT FROM AUTHOR]

The Cnidaria phylum includes organisms that are among the most poisonous animals. The exact composition of cnidarian bioactive molecules is not known in detail, but little is known on the cells that produce the toxins. Here we have shown that the presence of cytolysins is not exclusive of nematocysts. A plaque-forming assay was carried out with cell populations extracted from the percoled body fluid showed for the first time that anthozoan granulocytes are able to form plaque of lysis. We have partitioned the total population of free cells into three distinct discrete bands by discontinuous Percoll gradient, and we have identified six small different types cells: morular granulocytes; cells with large or small peripherical granules, granulocytes with irregular shape containing blue and red granules, cells showing one fine red granule of uniform size and, finally, cells with elongated shape and small dispersed granules. Cell lysate of each cellular band resulted cytolytic toward different erythrocytes types. SDS page analysis of the lysate cell fraction showed a predominant of 20 kDa that corresponds to the weight of the cytolytic equinatoxin. The nature of equinatoxins-related activity was demonstrated by inhibition experiments using bovine sphingomyelin.

The mucus produced by many marine organisms is a complex mixture of proteins and polysaccharides forming a weak watery gel. It is essential for vital processes including locomotion, navigation, structural support, heterotrophic feeding and defence against a multitude of environmental stresses, predators, parasites, and pathogens. In the present study we focused on mucus produced by a benthic cnidarian, the sea anemone Actinia equina (Linnaeus, 1758) for preventing burial by excess sedimentation and for protection. We investigated some of the physico-chemical properties of this matrix such as viscosity, osmolarity, electrical conductivity, protein, carbohydrate, and total lipid contents. Some biological activities such as hemolytic, cytotoxic, and antibacterial lysozyme-like activities were also studied. The A. equina mucus is mainly composed by water (96.2% ± 0.3%), whereas its dry weight is made of 24.2% ± 1.3% proteins and 7.8% ± 0.2% carbohydrates, with the smallest and largest components referable to lipids (0.9%) and inorganic matter (67.1%). The A. equina mucus matrix exhibited hemolytic activity on rabbit erythrocytes, cytotoxic activity against the tumor cell line K562 (human erythromyeloblastoid leukemia) and antibacterial lysozyme-like activity. The findings from this study improve the available information on the mucus composition in invertebrates and have implications for future investigations related to exploitation of A. equina and other sea anemones' mucus as a source of bioactive compounds of high pharmaceutical and biotechnological interest. [ABSTRACT FROM AUTHOR]

Contest theory predicts the evolution of a stable mixture of different strategies for fighting. Here, we investigate the possibility that stable between-individual differences in startle-response durations influence fighting ability or ‘resource-holding potential’ (RHP) in the beadlet sea anemone, Actinia equina. Both winners and losers showed significant repeatability of pre-fight startle-response durations but mean pre-fight startle-response durations were greater for eventual losers than for eventual winners, indicating that RHP varies with boldness. In particular, individuals with short startle responses inflicted more attacks on their opponent. Both repeatability and mean-level responses were changed by the experience of fighting, and these changes varied with outcome. In losers, repeatability was disrupted to a greater extent and the mean startle-response durations were subject to a greater increase than in winners. Thus, following a fight, this behavioural correlate of RHP behaves in a way similar to post-fight changes in physiological status, which can also vary between winners and losers. Understanding the links between aggression and boldness therefore has the potential to enhance our understanding of both the evolution of animal personality and the ‘winner and loser effects’ of post-fight changes in RHP. [ABSTRACT FROM AUTHOR]

Contest behavior, where individuals compete directly against one another for access to limited resources, is widespread across animal taxa. In many cases, contests are settled though the use of noninjurious behavior such as agonistic signals and even fights that involve weapons are often resolved through processes of assessment and strategic decision making. Here, we determine the role of these “decision rules” during staged contests in a simple animal, the beadlet sea anemone Actinia equina using a recently suggested approach of analyzing 1) traits linked to resource holding potential (RHP), 2) relationships between RHP and contest duration, and 3) contest dynamics. Depending on the activities used in the encounter, RHP, is linked to overall body size, the size of stinging nematocyst weapons, or by the ability to land blows on the opponent. Furthermore, changes in the intensity of aggression as the contest progresses indicate the use of 2 distinct types of self-assessment-based decision rules, which differ according to whether weapons are used in the contest. Therefore, these fights in animals that lack a centralized nervous system appear to involve the use of logical decision rules similar to those observed in contests in animals that are often assumed to be more “complex” in their behavior. Indeed, anemones appear to use different sources of information about incurred costs, depending on the intensity of the contest. [ABSTRACT FROM PUBLISHER]

Animal personality' means that individuals differ from one another in either single behaviours or suites of related behaviours in a way that is consistent over time. It is usually assumed that such consistent individual differences in behaviour are driven by variation in how individuals respond to information about their environment, rather than by differences in external factors such as variation in microhabitat. Since behavioural variation is ubiquitous in nature we might expect 'animal personality' to be present in diverse taxa, including animals with relatively simple nervous systems. We investigated in situ startle responses in a sea anemone, Actinia equina, to determine whether personalities might be present in this example of an animal with a simple nervous system. We found very high levels of repeatability among individuals that were re-identified in the same locations over a three week sampling period. In a subset of the data, where we used tidepool temperature measurements to control for a key element of variation in microhabitat, these high levels of repeatability remained. Although a range of other consistent differences in micro-habitat features could have contributed to consistent differences between the behaviour of individuals, these data suggest the presence of animal personality in A. equina. Rather than being restricted to certain groups, personality may be a general feature of animals and may be particularly pronounced in species with simple nervous systems. [ABSTRACT FROM AUTHOR]

The article discusses a study on the diet of intertidal Actinia equina found at different heights on shores of various wave exposure levels in Ireland. The study involved sea anemones collected on falling tides within a few minutes of the tide living them in summer 2009. The diet of sea anemones found at the exposed shore and the lower part of the semi-exposed shore was dominated by molluscs. Results showed that shore exposure and shore height influence the coelenteron contents of A. equina. Also noted is the preference of A. equina for dead or damaged animals given the fact that mussels with cut adductor muscles were fully digested by the organism.

Abstract: The population genetics of most cnidarians remain poorly understood, in part due to the complexities of their modes of reproduction and hybridization among closely related species. Actinia equina is the most common species of sea anemone along coastal areas in Europe and the Mediterranean. Members of this species vary in reproductive modes and presumably in genetic diversity among sites. Here we follow genetic variation of Actinia populations along the Mediterranean coasts of Israel, at the southern limit of the species range. Three sites, Yafo, Mikhmoret and Akhziv (south to north along a distance of 120 km; showing a decreased abundance of polyps towards the south) were chosen. Genetic profiles using amplified fragment length polymorphism (AFLP) markers indicated that each individual had a unique banding pattern and thus a distinct genetic identity. This suggests exclusive sexual reproduction, in contrast to clonal replication known in other Actinia populations. Nei''s mean genetic distance analysis revealed that all three studied populations interbreed, marked by reduced genetic diversity and polymorphism in the northernmost population at Akhziv. The Israeli populations exhibit a higher genetic polymorphism than other Actinia populations from the Mediterranean Sea. We conclude that environmentally stressful conditions, especially high temperatures at the southernmost limit of this species in the Mediterranean, restrict these populations to sexual reproduction, generating higher levels of genetic heterogeneity. [Copyright &y& Elsevier]

Abstract: Sea anemones are rich in biologically active polypeptides such as toxins and protease inhibitors. These polypeptides have so far been isolated from whole bodies, tentacles or secreted mucus. Recently, two novel peptide toxins with crab lethality have been isolated from acrorhagi (specialized aggressive organs elaborated by only certain species of sea anemones belonging to the family Actiniidae) of Actinia equina. This prompted us to survey biologically active polypeptides in the acrorhagi of two species of sea anemones, Anthopleura aff. xanthogrammica and Anthopleura fuscoviridis. No potent crab lethality was displayed by the acrorhagial extracts of both species. However, significantly high protease inhibitory activity was instead detected in the acrorhagial extracts of the two species and also in that of A. equina. From the acrorhagi of A. equina, A. aff. xanthogrammica and A. fuscoviridis, one (AEAPI), one (AXAPI) and two (AFAPI-I and AFAPI-III) protease inhibitors were isolated, respectively. The complete amino acid sequences of the four inhibitors were elucidated by N-terminal sequencing and sequencing of the C-terminal peptide fragment produced upon asparaginylendopeptidase digestion. The determined amino acid sequences revealed that all the four inhibitors are new members of the Kunitz-type protease inhibitor family. [Copyright &y& Elsevier]

Abstract: Venomous organisms are usually resistant to their own venoms, and utilize mechanical behavioral means to resolve intra-specific conflicts, such as those occurring over territory, mates or social status. The present study deals with a venom apparatus, which has been specifically designed for conspecific aggression, by the aid of a unique pharmacology. Actinarian sea anemones such as Actinia equina utilize vesicular organs termed acrorhagi in order to deter conspecific territorial competitors. The territorial aggression was shown to be performed by the aid of acrorhagial cnidocysts, which inflict localized tissue necroses on the body of the approaching–threatening anemone. In view of the fact that sea anemones were shown to resist mechanical injuries and their own cytolytic, necrosis-inducing pore-forming substances—the above acrorhagial injuries are ambiguous. Using an electrical device to collect acrorhagial cnidocyst-derived venom, we have shown that the venom is devoid of paralytic–neurotoxic activity, contains heat denaturable hemolytic polypeptides of a low molecular weight and is capable of inducing intracellular formation of reactive oxygen species (ROS) upon medium application to various cultured cells. The ROS formation phenomenon provides a reasonable pharmacological solution to the, above-mentioned, paradoxical conspecific self-intoxication by triggering a preexisting global endogenous mechanism of oxygen toxicity common to aerobic organisms. [Copyright &y& Elsevier]

Abstract: The compositions of the volatile and polar fractions from two coexisting Black Sea invertebrates, the mussel Mytilus galloprovincialis and the beadlet anemone Actinia equina, were established. The main metabolites in the volatile fraction from the investigated animals appeared to be methyl esters of fatty acids and fatty aldehydes. In the polar fraction from both animals low concentrations of free acids and nitrogen-containing compounds were obtained. Free carbohydrates were in much higher concentrations in M. galloprovincialis than in A. equina. Some sterols, probably as polar conjugates, were identified mainly in A. equina. Significant changes among all compounds appeared after treatment of both invertebrates with two different concentrations of cobalt ions. The variety of changes in each invertebrate could be due to their different evolutionary status. The effect of cobalt ions was often stronger at medium cobalt-ion concentrations. [Copyright &y& Elsevier]

Abstract: The lipid and sterol fractions of the mussel Mytilus galloprovincialis and the anemone Actinia equina were analyzed before and after incubation with cobalt ions. There were significant changes in the lipid and sterol composition, strongly depending on the cobalt ions concentrations. The changes in the lipid composition of both invertebrates were different for neutral lipids and phospholipids. These changes concern the length of the fatty acid chains as well as their unsaturation. The cobalt ions inhibited the oxidation of sterols and their alkylation at C-24. Because of these results we can assume that some of the changes caused by cobalt ions might possess adaptive value. [Copyright &y& Elsevier]

Abstract: Two peptide toxins, acrorhagin I (50 residues) and II (44 residues), were isolated from special aggressive organs (acrorhagi) of the sea anemone Actinia equina by gel filtration on Sephadex G-50 and reverse-phase HPLC on TSKgel ODS-120T. The LD50 against crabs of acrorhagin I and II were estimated to be 520 and 80μg/kg, respectively. 3′- and 5′-RACE established the amino acid sequences of the acrorhagin precursors. The precursor of acrorhagin I is composed of both signal and mature peptides and that of acrorhagin II has an additional sequence (propart) between signal and mature peptides. Acrorhagin I has no sequence homologies with any toxins, while acrorhagin II is somewhat similar to spider neurotoxins (hainantoxin-I from Selenocosmia hainana and Tx 3-2 from Phoneutria nigriventer) and cone snail neurotoxin (ω-conotoxin MVIIB from Conus magus). In addition, analogous peptides (acrorhagin Ia and IIa) were also cloned during RT-PCR experiments performed to confirm the nucleotide sequences of acrorhagins. This is the first to demonstrate the existence of novel peptide toxins in the sea anemone acrorhagi. [Copyright &y& Elsevier]

Polyps of Actinia equina are the most common sea anemones in the rocky intertidal zone of the Mediterranean coast of Israel, where they occur in one of the southernmost populations of this species in the northern hemisphere. We examined effects of feeding rate on polyp growth at ambient sea temperature for this population. Under laboratory conditions, polyps were left unfed, or were fed with brine shrimp (Artemia) once every 2 weeks, once a week, or twice a week. Of the four experimental treatments, only feeding twice a week resulted in polyp growth; under all other regimes, the sea anemones lost body mass. We conclude that a high rate of feeding is required at sea temperatures in the eastern Mediterranean, where these sea anemones may have high metabolic rates relative to more northern populations. [Copyright &y& Elsevier]

Among eighteen point mutants of equinatoxin II produced in E. coli, containing a single cystein substitution at variable position, EqtIIK77C was chosen for its peculiar properties. It was almost 100 times less hemolytic than the wild-type, but its hemolytic activity could be restored by chemical modification of the thiol group, provided that a positive charge was reintroduced. This indicates that a positive charge at this position is necessary for toxin activity. The mutant formed larger pores as compared to the wild type, but displayed the same cation selectivity. The pores reverted to normal size upon reintroduction of the positive charge. The conformation of EqtIIK77C and its binding to lipid membranes, either vesicles or red blood cells, was almost normal. However the kinetics of calcein release from lipid vesicles was substantially slower than that of the wild-type. Taken together with the different size of the pore formed, this is an indication that mutation of Lys77 --> Cys influences the normal development of the aggregate which is required for assembling the functional pore. [ABSTRACT FROM AUTHOR]

Reveals that intrinsic tryptophan fluorescence of equinatoxin II, a pore-forming polypeptide from the sea anemone Actinia equina L, monitors its interaction with lipid membranes.

Highlights: [•] Contests occur when rivals compete over indivisible resources. [•] Contests may involve injurious or non-injurious behaviour. [•] We investigated the effects of relatedness on the use of injurious stings during contests in sea anemones. [•] The likelihood of stinging increased with the degree of relatedness between opponents. [ABSTRACT FROM AUTHOR]

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