1,721,016 research outputs found
Different demographic responses of the polychaete Dinophilus gyrociliatus to metal exposure.
No full textThe purpose of this study was to investigate in comparison the sensitivity of some populationparameters such as the population growth rate l, the life expectancy e0 and the net reproduction rate R0estimated for cohorts of Dynophilus gyrociliatus exposed to different heavy metals. Comparison of thesurvival, fecundity and demographic indices of a laboratory culture of D. gyrociliatus between two treatedcohorts kept in artificial seawater enriched with nominal concentrations of 1.00 mg Zn/ml added as ZnCl2 and1.00 mg Cr/ml added as Cr Cl3 respectively, and two control groups was performed. The net growth rate, R0,appeared the demographic parameter most sensitive to metal enrichment: in fact both zinc and trivalentchromium determined a sharp decline of R0 with respect to controls. To a lesser extend life expectancy, e0,was also reduced by zinc and chromium, while metal enrichment did not affect the population growth rate, l.Although l is often used as index of population fitness, the variations of R0 due to pollutants should not beunderestimated from a population biology perspective. Considering all demographic effects of a toxicant ontarget organisms would appear to be a precautionary means to ensure the maintenance of wild populations
Ecotoxicity of hallachrome, an unusual 1-2 anthraquinone excreted by the infaunal polychaete Halla parthenopeia: evidence for a chemical defence?
Full text linkPolychaetes play a prominent role in marine systems, but little is known about their secondary metabolites compared with other benthic taxa. In the present study, we investigated the toxicity of hallachrome, an unusual 1-2 anthraquinone identified from the skin of some polychaetes, including the Mediterranean infaunal species Halla parthenopeia. Under stress conditions, this worm releases a harmful purple mucus, whose noxious compounds were still unknown. We hypothesized that hallachrome also occurs in the purple mucus, giving rise to its color and toxicity. Soon after the production of the purple exudate, H. parthenopeia also secretes a harmless, transparent mucus, which pushes away the toxic one, suggesting protective functions for the worm itself. LC-MS and H-1-NMR analyses confirmed the presence of the pigment hallachrome in the purple mucus. The average concentration of the pigment in the purple mucus was about 310 mg L-1. Ecotoxicological bioassays on representative species of bacteria, protozoans, rotifers, crustaceans (Artemia franciscana) and polychaetes (Dinophilus gyrociliatus) revealed its severe toxic effects: LC50/EC(50)values ranged from 0.11-5.67 mg L-1. Hallachrome showed higher toxicity for A. franciscana than other naturally occurring anthraquinones. Tests on encapsulated embryos of D. gyrociliatus evidenced the ability of a mucus layer to limit hallachrome diffusion, confirming the protective role of the transparent mucus. Given the information available on polychaetes anti-predator strategies, hallachrome cannot be considered a consumer deterrent. However its toxicity and wide range of activity suggest chemical defensive functions against potential competitors, parasites and/or pathogens
Response to Tilic and Bartolomaeus's Commentary on the original Research Paper “Unravelling the ultrastructure and mineralogical composition of fireworm stinging bristles” (Zoology, 144)
No full textIn their Commentary to our paper recently published in Zoology (Righi et al., 2021a), Tilic and Bartolomaeus question our findings that the chaetae of Hermodice carunculata (Annelida) are hollow and able to store and deliver venoms. They sustain the idea that inflammatory chemicals are secreted through epidermal glands and possibly exposed to predator trough wounds caused by the brittle chaetae. We provide evidence-based arguments in support of our considerations. The sample preparation procedures did not affect the native inner structure of unfixed fireworm chaetae, which is clearly hollow as supported by both ultrastructure observation and crystal-chemical analysis of constituents. Furthermore, our previous and more recent feeding bioassays and chemical analysis indicate both that chaetae retain strong deterrent capacities even when isolated from the body of H. carunculata, and that they contain venoms. The cellular mechanisms involved in fireworm chaeta storage and deliver of chemicals are still unstudied. We strongly believe that this lack of knowledge should draw further attention on H. carunculata biology, pursuing new hypotheses and studies based on the noteworthy information which has been obtained so far
Optimal growth and feeding behaviour of the valuable bait Halla parthenopeia (Polychaeta: Oenonidae) in small-scale rearing systems
Full text linkGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Exploring the Antimicrobial Potential of Hallachrome, a Defensive Anthraquinone from the Marine Worm Halla parthenopeia (Polychaeta)
Full text linkAntimicrobial resistance is a critical global health issue, with rising resistance among bacteria and fungi. Marine organisms have emerged as promising, but underexplored, sources of new antimicrobial agents. Among them, marine polychaetes, such as Halla parthenopeia, which possess chemical defenses, could attract significant research interest. This study explores the antimicrobial properties of hallachrome, a unique anthraquinone found in the purple mucus of H. parthenopeia, against Gram-negative bacteria (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 9027), Gram-positive bacteria (Enterococcus faecalis ATCC 29212, Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 12228), and the most common human fungal pathogen Candida albicans ATCC 10231. Antibacterial susceptibility testing revealed that Gram-negative bacteria were not inhibited by hallachrome at concentrations ≤2 mM. However, Gram-positive bacteria showed significant growth inhibition at 0.12–0.25 mM, while C. albicans was inhibited at 0.06 mM. Time-kill studies demonstrated dose-dependent growth inhibition of susceptible strains by hallachrome, which exerted its effect by altering the membrane permeability of C. albicans, E. faecalis, and S. epidermidis after 6 h and S. aureus after 24 h. Additionally, hallachrome significantly reduced biofilm formation and mature biofilm in S. aureus, E. faecalis, and C. albicans. Additionally, it inhibited hyphal growth in C. albicans. These findings highlight hallachrome’s potential as a novel antimicrobial agent, deserving further exploration for clinical experimentation
Predazione di Hermodice carunculata (Annelida: Amphinomidae) su esacoralli (Anthozoa)
No full textThe ability of the polychaete Hermodice carunculata to prey on some species of hexacorals was assessed through laboratory feeding experiments. Soft corals and sea anemones were almost completely consumed, while the carbonatic skeleton of hard corals seems to discourage polychaetes from consumption. The results highlighted the capacity of Mediterranean H. carunculata to prey on a wide range of anthozoans
Organic enrichment effects on a marine meiofauna community, with focus on Kinorhyncha
No full textWithin the framework of a programme aimed at monitoring the impact of fish farming on the marine biota, we have had the opportunity to study the effect of the organic enrichment caused by the fish farm on meiofauna abundances and Kinorhyncha communities’ structure over two farming cycles. Up to now, studies on kinorhynchs have focussed mostly on the taxonomy, biogeography, and the ultrastructure, and, more recently, on the phylogenetic aspects of the taxon. Only few studies have dealt with the ecology of these creatures and studies focusing on the response of these animals to disturbances of anthropogenic origin are rare. The study took place in the Western Mediterranean and fauna was investigated based on three replicate cores collected from eight sites: one beneath the farm, four along a transect with increasing distances from the farm, and three control sites. Density data from beneath the cage and the three control sites was analysed within a beyond-B.A.C.I. (Before-After, Control-Impact) with asymmetrical sampling design, while a Before-After approach was used to analyse data from other sites. The latter approach was applied also to investigate the environmental variables from all the surveyed sites. Overall, 21 major meiofaunal groups were found in the area, with total densities ranging from 595 to 6818 ind/10 cm2. We recorded a variation of the densities of several taxa after each cycle. In particular, we observed a significant increase of the total meiofauna and nematodes abundances, and a marked decrease of kinorhynchs diversity and density at the sites beneath and near the farming ‘Cage’. Conversely, kinorhynch density increased at sites far from the farm. Kinorhynchs were present with ten species, including a representative of the rare genus Condyloderes, and densities up to more than 245 ind./10 cm2. Analyses indicate that kinorhynchs are particularly sensitive to sulfides. Accumulation of organic matter and high concentration of sulfides caused a marked reduction or even the disappearance of kinorhynchs. If confirmed by additional studies, the nematodes/kinorhynchs ratio could be used as simple and useful tool for the assessment of organic enrichment in marine environments, especially in muddy bottoms
Unravelling the ultrastructure and mineralogical composition of fireworm stinging bristles
No full textAmphinomid fireworms are notorious for their stinging dorsal bristles (notochaetae), but it is still unclear whether the irritation they cause is merely mechanical or if the notochaetae contain toxins. Furthermore, although fireworm chaetae have always been described as calcareous, their composition has never been investigated to date and strong debates are ongoing on their internal structure. Unravelling the native ultrastructure and composition of fireworm chaetae is the first crucial step to assess whether the hypothesis of toxin vehiculation could be fully considered. We examined for the first time the chemical and mineralogical composition, the ultrastructure and the external structure of the dorsal and ventral chaetae of the large species Hermodice carunculata. All the measurements were carried out on samples prepared without the use of chemical reagents, except for those targeted to investigate if decalcification altered the ultrastructure of the chaetae. A crystal-chemical strategy, combining chemical, diffraction and thermal analyses clearly showed the occurrence of crystalline calcium carbonate and clusters of phosphatic amorphous material. Scanning electron micrographs and energy dispersive X-ray measurements showed that the dorsal chaetae have an extremely shallow insertion point in the body respect to the ventral chaetae, that could facilitate the release of the notochaetae in the environment. Their proximal part is characterized by canals with a hexagonal pattern rich in Ca and P, followed by a large cavity upwards. The harpoon-shaped ends and the central canals of the notochaetae completely disappeared after exposure to EDTA. The notochaetae are hollow and may be able to vehicle toxins. The absence of the honeycomb pattern in the distal part of the notochaetae and their slenderness probably contribute to their brittleness and high sensitivity to breakage on contact. These observations constitute keystone understandings to shed light on fireworm defensive and offensive capacities and their ecological success
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