Total oxyradical scavenging capacity of the deep-sea amphipod Eurythenes gryllus

Environmental concern for the deep-sea ecosystem is increasing as contaminants, originating from anthropogenic activities, have been detected in deep-sea biota. However, little is known on the xenobiotics metabolising capability of deep-sea fauna. In this study, the deep-sea amphipod Eurythenes gryllus was selected as sentinel species to measure the total oxyradical scavenging capacity (TOSC). Individuals of E. gryllus were sampled at 2000 m depth in the Arctic Ocean. The TOSC assay was measured on the cytosolic fraction and the soluble fraction (3 kDa) of the digestive gland and on the cell-free haemolymph toward peroxyl, hydroxyl and peroxynitrite radicals according to the method of Winston et al. [Free Radical Biology and Medicine 24 (3) (1998) 480] and Regoli and Winston [Toxicology and Applied Pharmacology 156 (1999) 96]. These results provide the first baseline data set for total antioxidant capacity in a deep-sea amphipod.     

Time-course evaluation of ROS-mediated toxicity in mussels, Mytilus galloprovincialis, during a field translocation experiment

Harbours can be considered as model environments for developing and validating field monitoring procedures and to investigate mechanistic relationships between different biological responses. In this study several biomarkers were investigated in marine mussels caged for 4 weeks (June-July 2001) into an industrialized harbour of NW Italy. Organisms were collected at different time-intervals to better characterize the sensitivity, temporal variations and interactions of analysed responses. Besides single antioxidants the total oxyradical scavenging capacity (TOSC) assay was used to analyse the capability of the whole antioxidant system to neutralize specific forms of radicals: these data were further integrated by measurement of DNA integrity, oxidized bases and the impairment of lysosomal membrane stability in haemocytes. Results showed a biphasic trend for single antioxidants and TOSC, with an increase during the first 2 weeks of exposure to the polluted site followed by a progressive decrease up to a severe depletion in the final part of the experiment.     

Time-course evaluation of ROS-mediated toxicity in mussels, Mytilus galloprovincialis, during a field translocation experiment

Harbours can be considered as model environments for developing and validating field monitoring procedures and to investigate mechanistic relationships between different biological responses. In this study several biomarkers were investigated in marine mussels caged for 4 weeks (June–July 2001) into an industrialized harbour of NW Italy. Organisms were collected at different time-intervals to better characterize the sensitivity, temporal variations and interactions of analysed responses. Besides single antioxidants the total oxyradical scavenging capacity (TOSC) assay was used to analyse the capability of the whole antioxidant system to neutralize specific forms of radicals: these data were further integrated by measurement of DNA integrity, oxidized bases and the impairment of lysosomal membrane stability in haemocytes. Results showed a biphasic trend for single antioxidants and TOSC, with an increase during the first 2 weeks of exposure to the polluted site followed by a progressive decrease up to a severe depletion in the final part of the experiment.     

Total oxyradical scavenging capacity and cell membrane stability of haemocytes of the Arctic scallop,Chlamys islandicus,following benzo(a)pyrene exposure

Industrial activities, notably oil and gas industries, are expanding in the Arctic. Most of the biomarkers were developed using temperate organisms living at temperatures above 10 degrees C. Little is known about the biomarker responses of organisms living between -1.88 and 5 degrees C. Therefore, assessment of the toxicity of chemicals to cold-water adapted species is required. In this study, the Arctic scallop, Chlamys islandicus, was selected as a key species for bio-monitoring because of wide distribution in Arctic waters and its commercial value. Test animals, stored in seawater at 2 degrees C, were injected with benzo(a)pyrene (diluted in cod liver oil 5 mg ml(-1)) in the adductor muscle every 24 h for four days giving a final dose of 0, 74 and 90.6 mg kg(-1) wet weight for control, low and high dose, respectively. The biomarkers used were total oxyradical scavenging capacity (TOSC) in the digestive gland and cell membrane stability of haemocytes. TOSC values were significantly reduced (ca. 30%) in exposed groups (P < 0.05), indicating a depletion in oxyradical molecular scavengers. The antioxidant defences appeared to be overwhelmed by the reactive oxygen species as the plasma membranes of haemocytes were destabilised (P < 0.05) probably due to lipid peroxidation. These data indicate that reactive oxygen species (ROS) were produced by Arctic scallops via the metabolisation of benzo(a)pyrene at 2 degrees C.     

Oxidative stress in ecotoxicology: from the analysis of individual antioxidants to a more integrated approach

An integrate approach will be discussed for investigations on oxidative stress in xenobiotic toxicity. While the analysis of individual antioxidants is useful for their sensitivity and to understand the mode of action of a stressor, the integration with the analysis of the total antioxidant capacity provides a more holistic assessment of the overall biological significance of such variations. TOSC has a greater predictive value on the health condition of the organisms and allows to discriminate the different role of specific ROS in oxidative stress syndrome.     

Mediterranean deep-sea amphipods: composition, structure and affinities of the fauna

The recent revision of the Mediterranean amphipod fauna includes 415 species (i.e. 8% of the worldwide fauna). The number of endemic species is estimated to be about 190 (i.e. 46% of the total fauna).The deep-sea fauna, which includes all those species inhabiting depths >150m, comprises 154 species (37.1% of the total fauna), belonging to 89 genera and 25 families. 84 of these species inhabited depths down to 400m, 47 down to 1000m, and 31 to depths >2000m. Considering the upper limits to their bathymetric ranges, 49 species are restricted to depths >150m, 15 to >400m, 9 to >1000m and just 5 to depths >2000m. 62.9% of the gammaridean fauna is restricted to the continental shelf at depths shallower than 150m. Only 11.3% of this fauna inhabits depths >1000m. and only 2.2% is restricted to these deeper depths.The composition of this deep-living fauna has complex zoogeographical relationships. There are four main categories of species: eurybathic, Atlantico-Mediterranean bathyal, endemic bathyal and endemic abyssal species.The deep-living species include 71 (46%) which are endemic. There are also 71 species which zoogeographically are Atlantico-Mediterranean, 4 which are cosmopolitan, 5 Atlantico-Pacifico-Mediterranean, one Indo-Atlantico-Mediterranean and one Pacifico-Mediterranean. The 71 endemic species belonging to 52 genera. Three of these genera are endemic and five others were previously known only as Indo-Pacific.The presence of bathyal endemic species belonging to bathyal genera, and the affinity of some other species otherwise occurring only in the Indo-Pacific, confirms that a Tethyan component persists in the amphipod fauna, and indicates that during the Messinian Crisis the Mediterranean did not completely dry up. Thus a relict amphipod fauna was able to survive in some of the residual basins.     

The response of abyssal organisms to low pH conditions during a series of CO2-release experiments simulating deep-sea carbon sequestration

The effects of low-pH, high-pCO₂ conditions on deep-sea organisms were examined during four deep-sea CO₂ release experiments simulating deep-ocean C sequestration by the direct injection of CO₂ into the deep sea. We examined the survival of common deep-sea, benthic organisms (microbes; macrofauna, dominated by Polychaeta, Nematoda, Crustacea, Mollusca; megafauna, Echinodermata, Mollusca, Pisces) exposed to low-pH waters emanating as a dissolution plume from pools of liquid carbon dioxide released on the seabed during four abyssal CO₂-release experiments. Microbial abundance in deep-sea sediments was unchanged in one experiment, but increased under environmental hypercapnia during another, where the microbial assemblage may have benefited indirectly from the negative impact of low-pH conditions on other taxa. Lower abyssal metazoans exhibited low survival rates near CO₂ pools. No urchins or holothurians survived during 30–42 days of exposure to episodic, but severe environmental hypercapnia during one experiment (E1; pH reduced by as much as ca. 1.4 units). These large pH reductions also caused 75% mortality for the deep-sea amphipod, Haploops lodo, near CO₂ pools. Survival under smaller pH reductions (ΔpH<0.4 units) in other experiments (E2, E3, E5) was higher for all taxa, including echinoderms. Gastropods, cephalopods, and fish were more tolerant than most other taxa. The gastropod Retimohnia sp. and octopus Benthoctopus sp. survived exposure to pH reductions that episodically reached −0.3 pH units. Ninety percent of abyssal zoarcids (Pachycara bulbiceps) survived exposure to pH changes reaching ca. −0.3 pH units during 30–42 day-long experiments.     

Cellular energy allocation in the Arctic sea ice amphipod Gammarus wilkitzkii exposed to the water soluble fractions of oil

Increasing offshore oil and gas activities in the European Arctic has raised concerns of the potential anthropogenic impact of oil-related compounds on the polar marine ecosystem. We measured cellular energy allocation (CEA) in the sea ice amphipod Gammarus wilkitzkii after exposure for one month to the water soluble fraction (WSF) of oil. The CEA biomarker measures the energy budget of organisms by biochemically assessing changes in carbohydrates, protein and lipid content as well as the electron transport system activity. A significantly higher protein content was observed in the medium dose compared to controls, while the total energy budget was not affected in G. wilkitzkii. This indicates that parts of the energy budget of G. wilkitzkii, which is a key species in the Arctic ecosystem, is affected by a WSF of oil.     

Total oxyradical scavenging capacity and cell membrane stability of haemocytes of the Arctic scallop, Chlamys islandicus, following benzo(a)pyrene exposure

Industrial activities, notably oil and gas industries, are expanding in the Arctic. Most of the biomarkers were developed using temperate organisms living at temperatures above 10 °C. Little is known about the biomarker responses of organisms living between −1.88 and 5 °C. Therefore, assessment of the toxicity of chemicals to cold-water adapted species is required. In this study, the Arctic scallop, Chlamys islandicus, was selected as a key species for bio-monitoring because of wide distribution in Arctic waters and its commercial value. Test animals, stored in seawater at 2 °C, were injected with benzo(a)pyrene (diluted in cod liver oil 5 mg ml⁻¹) in the adductor muscle every 24 h for four days giving a final dose of 0, 74 and 90.6 mg kg⁻¹ wet weight for control, low and high dose, respectively. The biomarkers used were total oxyradical scavenging capacity (TOSC) in the digestive gland and cell membrane stability of haemocytes. TOSC values were significantly reduced (ca. 30%) in exposed groups (P<0.05), indicating a depletion in oxyradical molecular scavengers. The antioxidant defences appeared to be overwhelmed by the reactive oxygen species as the plasma membranes of haemocytes were destabilised (P<0.05) probably due to lipid peroxidation. These data indicate that reactive oxygen species (ROS) were produced by Arctic scallops via the metabolisation of benzo(a)pyrene at 2 °C.     

Antioxidant efficiency and detoxification enzymes in spotted dogfish Scyliorhinus canicula

Although elasmobranchs are widely distributed species, commonly found on sandy, gravely or muddy bottoms, several biological aspects of their metabolism still remain poorly investigated. In this work the efficiency of antioxidant system and detoxification enzymes were investigated in the coastal spotted dogfish Scyliorhinus canicula and in the red mullet Mullus barbatus for comparison with a teleost species. Organisms were sampled during a bottom trawl survey and analyzed for the biotransformation activity (EROD), levels of metallothioneins, catalase, glutathione S-transferases and total oxyradical scavenging capacity (TOSC) toward peroxyl radicals and hydroxyl radicals. EROD activity in the elasmobranchs was more than one order of magnitude lower than in the red mullets, while similar levels of metallothioneins were measured in these species. S. canicula showed significantly lower antioxidant enzymes and a more reduced efficiency in neutralizing *OH; on the other hand the scavenging capability toward ROO* was comparable in S. canicula and M. barbatus.     

Environmental prognostics: an integrated model supporting lysosomal stress responses as predictive biomarkers of animal health status

The potential prognostic use of lysosomal reactions to environmental pollutants is explored in relation to predicting animal health in marine mussels, based on diagnostic biomarker data. Cellular lysosomes are already known to accumulate many metals and organic xenobiotics and the lysosomal accumulation of the carcinogenic polycyclic aromatic hydrocarbon 3-methylcholanthrene (3-MC) is demonstrated here in the hepatopancreatic digestive cells and ovarian oocytes of the blue mussel. Lysosomal membrane integrity or stability appears to be a generic indicator of cellular well-being in eukaryotes; and in bivalve molluscs it is correlated with total oxygen and nitrogen radical scavenging capacity (TOSC), protein synthesis, scope for growth and larval viability; and inversely correlated with DNA damage (micronuclei), as well as lysosomal swelling (volume density), lipidosis and lipofuscinosis, which are all characteristic of failed or incomplete autophagy. Integration of multiple biomarker data is achieved using multivariate statistics and then mapped onto "health status space" by using lysosomal membrane stability as a measure of cellular well-being. This is viewed as a crucial step towards the derivation of explanatory frameworks for prediction of pollutant impact on animal health; and has facilitated the development of a conceptual mechanistic model linking lysosomal damage and autophagic dysfunction with injury to cells, tissues and the whole animal. This model has also complemented the creation and use of a cell-based bioenergetic computational model of molluscan hepatopancreatic cells that simulates lysosomal and cellular reactions to pollutants. More speculatively, the use of coupled empirical measurements of biomarker reactions and modelling is proposed as a practical approach to the development of an operational toolbox for predicting the health of the environment.     

Contribution of trimethylamine N-oxide on the growth and pressure tolerance of deep-sea bacteria

Trimethylamine N-oxide(TMAO) is widely dispersed in marine environments and plays an important role in the biogeochemical cycle of nitrogen. Diverse marine bacteria utilize TMAO as carbon and nitrogen sources or as electron acceptor in anaerobic respiration. Alteration of respiratory component according to the pressure is a common trait of deep-sea bacteria. Deep-sea bacteria from dif ferent genera harbor high hydrostatic pressure(HHP) inducible TMAO reductases that are assumed to be constitutively expressed in the deep-sea piezosphere and facilitating quick reaction to TMAO released from ?sh which is a potential nutrient for bacterial growth. However, whether deep-sea bacteria universally employ this strategy remains unknown. In this study, 237 bacterial strains affliated to 23 genera of Proteobacteria,Bacteroidetes, Firmicutes and Actinobacteria were isolated from seawater, sediment or amphipods collected at dif ferent depths. The pressure tolerance and the utilization of TMAO were examined in 74 strains. The results demonstrated no apparent correlation between the depth where the bacteria inhabit and their pressure tolerance, regarding to our samples. Several deep-sea strains from the genera of Alteromonas, Halomonas,Marinobacter, Photobacterium, and Vibrio showed capacity of TMAO utilization, but none of the isolated Acinebacter, Bacillus, Brevundimonas, Muricauda, Novosphingobium, Rheinheimera, Sphingobium and Stenotrophomonas did, indicating the utilization of TMAO is a species-speci?c feature. Furthermore, we noticed that the ability of TMAO utilization varied among strains of the same species. TMAO has greater impact on the growth of deep-sea isolates of Vibrio neocaledonicus than shallow-water isolates. Taken together, the results describe for the ?rst time the TMAO utilization in deep-sea bacterial strains, and expand our understanding of the physiological characteristic of marine bacteria.     

“海龙Ⅲ”号ROV系统深海试验与应用研究

深海水下机器人主要用于深远海地质、矿物资源和生物调查研究,以及海洋石油工程服务等水下综合作业,能够实现深海近底高精度、长时间的定点取样作业及其他精细化调查。结合国内外深海ROV装备和技术发展现状,以新研发的6 000 m级"海龙Ⅲ"号ROV搭载"大洋一号"船执行的2018年南海综合海试和48航次为例,从深海试验流程和方法、浅水区功能测试、深水区功能测试、深海观测及取样功能测试等方面,详细阐述了ROV海上试验和应用作业过程,对作业水深、功率配置、水下运动能力、搭载能力等关键性能指标进行了试验验证。海上功能测试和试验性应用结果表明,"海龙Ⅲ"ROV各项性能指标满足设计要求,验证了系统在不同深度、不同地形条件下的观测取样作业能力,创新了深水ROV作业方法手段,分析得出此类装备目前在国内发展存在的不足之处,并结合实际应用提出后期改进计划,以期为深海ROV的海试应用提供技术参考。     

深海能源土含气储层力学特性三轴试验研究

为研究深海能源土在负压开采过程中含气储层的力学特性,基于含气土赋存理论,提出一种能够控制含气量及气泡大小的制样方法,通过GDS标准应力路径三轴试验系统,开展深海能源土含气储层的固结排水试验研究,分析深海能源土在不同黏土含量及不同含气量下的力学响应规律。研究结果表明：围压变化对深海能源土含气储层的抗剪强度峰值大小影响显著,围压越大抗剪强度峰值越高;黏土含量是决定应力应变曲线变化趋势的关键影响因素,黏土含量越高试样抗剪强度越低,试样抵抗应变软化效应的能力越强;含气土比饱和土体承载能力更低,且承载能力随含气量的增大呈衰减趋势;黏土含量和含气量是深海能源土含气储层抗剪强度指标的重要影响因素,黏土含量、含气量越高,土体自身的总抗剪强度值越低。     

Nucleic acid concentrations (DNA,RNA) in the continental and deep-sea sediments of the eastern Mediterranean: relationships with seasonally varying organic inputs and bacterial dynamics

In order to study temporal variations of the genetic material in the continental shelf and deep-sea sediments of the extremely oligotrophic Cretan Sea, samples were collected on seasonal basis from August 1994 to September 1995, with a multiple corer, at seven stations (from 40 to 1540 m depth). Surface sediments (0–1 cm) were sub-sampled and analyzed for nucleic acid content (DNA, RNA) and bacterial density. DNA concentrations in the sediments were high (on annual average, 25.0 μg g^-1) and declined with increasing water depth, ranging from 3.5 to 55.2 μg g^-1. DNA concentrations displayed wide temporal changes also at bathyal depths confirming the recent view of the large variability of the deep-sea environments. Also RNA concentrations decreased with increasing water depth (range: 0.4–29.9 μg g^-1). The ratio of RNA to DNA did not show a clear spatial pattern but was characterized by significant changes between sampling periods. DNA concentrations were significantly correlated with protein and phytopigment concentrations in the sediment, indicating a possible relationship with the inputs of primary organic matter from the photic layer. Bacterial densities were generally high (range: 0.9–4.6×10⁸ cells g^-1) compared to other deep-sea environments and decreased with increasing water depth. Estimates of the bacterial contribution to the sedimentary genetic material indicated that bacterial-DNA accounted, on annual average, for a small fraction of the total DNA pool (4.3%) but that bacterial-RNA represented a significant fraction of the total sedimentary RNA (26%). Bacterial contribution to nucleic acids increased, even though irregularly, with increasing depth. In deep-sea sediments, changes in RNA concentrations appear to be largely dependent upon bacterial dynamics. Estimates of the overall living contribution to the DNA pools (i.e. microbial plus meiofaunal DNA) indicated that the large majority (about 90%) of the DNA in continental and deep-sea sediments of the eastern Mediterranean was detrital. The non-living DNA pools reach extremely high concentrations up to 0.41 g DNA m^-2 cm^-1. Thus, especially in deep benthic habitats, characterized by low inputs of labile organic compounds, detrital DNA could represent a suitable and high quality food source or a significant reservoir of nucleic acid precursors for benthic metabolism.     

Distribution pattern of pelagic amphipods and its affecting facors in the East China Sea

1 IntroductionAmphipoda, an order of marine pelagic shell-fish, belongs to class Crustacea, subclass Malacost-raca (Chen and Shi,2002). Species of this ordercan be found all over the world, especially in tropi-cal and subtropical oceans. As fish diets, th…     

深海化能极端环境中劳盆拟刺铠虾(Munidopsis lauensis)的全长转录组测序分析

劳盆拟刺铠虾(Munidopsis lauensis)是一种十足目铠甲虾, 能够适应深海化能合成生态系统的极端环境, 但是其已知基因序列信息却很少。为此, 采用PacBio平台的SMRT测序技术对来自南海台西南冷泉劳盆拟刺铠虾的肝胰腺、鳃、肌肉和肠混合组织进行了三代全长转录组测序。通过聚类、校正、去冗余之后共获得28 811条高质量isoform, 平均长度为2 086 bp, N50长度为2 275 bp。使用Nr、SwissPort、KEGG、KOG数据库对转录本序列进行功能注释, 共有20 616 (71.56%)条isoform得到注释。进一步高级注释共获得21 848个蛋白编码序列, 共预测到537个转录因子、6 430个长链非编码RNA和10 060个SSRs位点。KEGG通路分析发现两条可能与劳盆拟刺铠虾适应深海化能极端生境相关的通路, 分别为过氧化物酶体通路和谷胱甘肽代谢通路。其中, 共有180条isoform被发现参与编码过氧化物酶体通路中的31个关键酶, 213条isoform参与谷胱甘肽代谢通路中19个关键酶的编码。基于全长转录组数据, 利用同源比对、功能结构域预测及系统发育树构建等方法对劳盆拟刺铠虾谷胱甘肽S-转移酶(GST)基因家族进行挖掘与鉴定, 共发现属于theta、delta、mu、kappa四种亚家族的20条GST候选序列。通过对劳盆拟刺铠虾全长转录组测序、功能注释和环境适应相关的重要基因及通路的分析, 不仅丰富了深海组学数据资源, 也为进一步揭示甲壳动物适应深海化能极端环境的分子机制奠定了基础。     

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, for monitoring the impact of an offshore platform in the Adriatic Sea

An ecotoxicological protocol with caged mussels, Mytilus galloprovincialis, was developed to evaluate the potential impact of an offshore gas platform in the central Adriatic Sea. Reference organisms were collected on a seasonal basis from an unpolluted site and transplanted for four weeks in both the sampling area and to the investigated platform. Chemical analyses of trace metals in mussel tissues were integrated with a multi-biomarker approach for the early detection of biological responses at several cellular targets. Induction of metallothioneins, peroxisomal proliferation and activity of acetylcholinesterase were measured as markers for specific classes of chemicals. Special attention was given to oxyradical metabolism and appearance of oxidative-mediated toxicity to reveal a more general onset of cellular disturbance. In addition to individual antioxidants (superoxide dismutase, catalase, glutathione S-transferases, glutathione reductase, Se-dependent and Se-independent glutathione peroxidases, and levels of total glutathione), the total oxyradical scavenging capacity (TOSC) allowed a quantification of the overall capability to neutralize specific forms of intracellular reactive oxygen species (ROS; i.e. peroxyl and hydroxyl radicals). Cellular damages were evaluated as lysosomal destabilization (membrane stability, accumulation of lipofuscin and neutral lipids), lipid peroxidation products (malondialdehyde) and DNA integrity (strand breaks and micronuclei); the air survival test was finally applied to evaluate the overall physiological condition of mussels. Concentration of trace metals (As, Ba, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Zn) revealed only limited variations in transplanted mussels during various experimental periods and such changes appeared partly related to natural fluctuations. Among biological responses, variations of antioxidants and lysosomal stability were confirmed as sensitive early warning signals for biological disturbance of both natural and anthropogenic origin. The presented protocol with caged mussels allowed marked biological effects caused by the investigated platform to be excluded, and represented a useful approach that is easy to extend for monitoring the impact of offshore activities in the Adriatic sea.     

A preliminary study of the Caprella scaura amphipod culture for potential use in aquaculture

The caprellid amphipod Caprella scaura Templeton, 1836 was investigated as a mass culture organism, for potential use as natural prey in aquaculture. C. scaura showed good population growth during 3 months of culturing with nauplii of Artemia sp. and microalgae as food source. A final mean population size of 12,510.67 individuals/tank and a maximum density of 10,460 individuals m^− 2 were obtained; a 50-fold increase of the initial population was observed. Juveniles were the most abundant stage in the culture (86.0% of total), followed by mature females (5.4%) and immature males (3.1%). Three kinds of plastic mesh with different complexity levels were used as artificial substrates for amphipods to attach to and shelter. There were no significant differences in the total number of individuals present on each kind of mesh, although female and male adults were more abundant in folded meshes with larger pore diameter. This research demonstrated that the caprellid amphipod C. scaura may be readily cultured at high densities with a variety of mesh morphologies allowing more efficient use of tank volume and improved handling.     

Antioxidant efficiency and detoxification enzymes in spotted dogfish Scyliorhinus canicula

Although elasmobranchs are widely distributed species, commonly found on sandy, gravely or muddy bottoms, several biological aspects of their metabolism still remain poorly investigated. In this work the efficiency of antioxidant system and detoxification enzymes were investigated in the coastal spotted dogfish Scyliorhinus canicula and in the red mullet Mullus barbatus for comparison with a teleost species.Organisms were sampled during a bottom trawl survey and analyzed for the biotransformation activity (EROD), levels of metallothioneins, catalase, glutathione S-transferases and total oxyradical scavenging capacity (TOSC) toward peroxyl radicals and hydroxyl radicals.EROD activity in the elasmobranchs was more than one order of magnitude lower than in the red mullets, while similar levels of metallothioneins were measured in these species. S. canicula showed significantly lower antioxidant enzymes and a more reduced efficiency in neutralizing ^√OH; on the other hand the scavenging capability toward ROO^√ was comparable in S. canicula and M. barbatus.