Resistance to heavy metals of heterotrophic bacteria isolated from the deep-sea hydrothermal vent polychaete, Alvinella pompejana

Fifty-two heterotrophic bacteria isolated from the deep-sea hydrothermal vent polychaete, Alvinella pompejana, were tested for susceptibility to cadmium, zinc, copper, arsenate and silver ions by an agar dilution technique. Metal resistance was exhibited 96% of the total isolates. The frequencies of resistance to heavy metals were: copper, 88%; zinc and arsenic, 58%; cadmium, 38%. However, strains demonstrated a high susceptibility to silver. 71% of the strains tested were multiresistant to metals.     

卤虫无节幼体的营养强化对黑斑口虾蛄(Oratosquilla kempi)幼体发育的影响

用扁藻、酵母、“鱼油 酵母”强化和“不强化”4种方式处理的卤虫无节幼体投喂黑斑口虾蛄各期幼体,比较不同强化方法对黑斑口虾蛄幼体成活率、变态率、生长速度及总脂与脂肪酸组成的影响。结果表明,3种方式强化12h后的卤虫无节幼体与对照组相比,总脂含量都有不同程度的增加。卤虫无节幼体的脂肪酸组成与强化方式密切相关,其中“鱼油 酵母”强化的卤虫无节幼体20∶5n-3(EPA)和22∶6n-3(DHA)占总脂肪酸的比例最高,分别为5·74%和4·84%。投喂强化后富含EPA和DHA的卤虫无节幼体,可增加黑斑口虾蛄幼体体内脂肪酸尤其是EPA和DHA等不饱和脂肪酸的含量,从而提高其幼体的成活率、变态率与发育速度。     

Uptake and metabolism of arsenate by anexic cultures of the microalgae Dunaliella tertiolecta and Phaeodactylum tricornutum

Axenic cultures of the microalgae species, Dunaliella tertiolecta and Phaeodactylum tricornutum were grown at arsenic (As) concentrations typically found in uncontaminated marine environments ( 2 µg L^− 1) under different phosphorus concentrations. D. tertiolecta accumulated higher arsenic concentrations (mean: 13.7 ± 0.7 µg g^− 1 dry mass) than P. tricornutum (mean: 1.9 ± 0.2 µg g−1 dry mass). Media phosphorus concentrations (0.6–3 mg/L) had little influence on microalgae growth rates or arsenic accumulation. Arsenic was present as lipid bound (29–38%; 4.2–9.5%), water-soluble (20–29%; 26–34%) and residue bound (41–45%; 57–69%) arsenic species in D. tertiolecta and P. tricornutum respectively. Hydrolysed lipids contained mostly glycerol arsenoribose (OH- ribose), dimethylarsinate (DMA) and inorganic arsenic (As(V)) moieties. Water-soluble species of microalgae were very different. D. tertiolecta contained inorganic arsenic (54–86%) with variable amounts of DMA (7.4–20%), arsenoriboses (5–25%) and traces of methylarsonate (MA) ( 1%). P. tricornutum contained mostly DMA (32–56%) and phosphate arsenoribose (PO₄-ribose, 23–49%) and small amounts of OH-ribose (3.8–6.5%) and As(V) (9–16%). Both microalgae contained an unknown cationic arsenic species. The residue fractions of both microalgae contained predominately inorganic arsenic (99–100%). These results show that at natural seawater arsenic concentrations, both algae take up substantial amounts of inorganic arsenic that is complexed with structural elements or sequestered in vacuoles as stable complexes. A significant portion is also incorporated into lipids. Arsenic is metabolised to simple methylated species and arsenoriboses.     

Effect of cadmium, copper and mercury on antioxidant enzyme activities and lipid peroxidation in the gills of the hydrothermal vent mussel Bathymodiolus azoricus

Metals are known to influence lipid peroxidation and oxidative status of marine organisms. Hydrothermal vent mussels Bathymodiolus azoricus live in deep-sea environments with anomalous conditions, including high metal concentrations. Although B. azoricus are aerobic organisms they possess abundant methano and thioautotrophic symbiotic bacteria in the gills. The enzymatic defences (superoxide dismutase (SOD), catalase (CAT), total glutathione peroxidase (Total GPx) and selenium-dependent glutathione peroxidase (Se–GPx)) and lipid peroxidation were determined in the gills of B. azoricus exposed to Cd (0.9 μM), Cu (0.4 μM) and Hg (0.1 μM) with different times of exposure. The experiments were performed in pressurized containers at 9 ± 1 °C and 85 bars.Results show that vent mussels possess antioxidant enzymatic protection in the gills. Cd and Cu had an inhibitory effect in the enzymatic defence system, contrarily to Hg. These enzymatic systems are not completely understood in the B. azoricus, since reactive oxygen species might be produced through other processes than natural redox cycling, due to hydrogen sulphide and oxygen content present. Also the symbiotic bacteria may play an important contribution in the antioxidant protection of the gills.     

大西洋庸鲽(Hippoglossus hipoglossus L.)精液脂肪酸分析及激素GnRHa诱导对其组成的影响

采用气相色谱检测的方法,进行大西洋庸鲽精液脂肪酸组成分析及激素GnRHa诱导对其组成影响的研究。结果表明,大西洋庸鲽精液中含量最高的脂肪酸种类为22:6n-3(DHA,二十二碳六烯酸),占总脂肪酸比例25.67%±0.94%;其次为16:0(PA,棕榈酸)、20:5n-3(EPA,二十碳五烯酸);重要必需不饱和脂肪酸20:4n-6(AA,花生四烯酸)含量较低,为1.76%±0.01%。精液中高不饱和脂肪酸(PUFA)含量较高,为44.25%±0.30%;饱和脂肪酸(SAT)含量为27.72%±0.22%。重要脂肪酸比例DHA/EPA为2.33±0.26;EPA/AA为6.30±0.51;n-3/n-6为9.22±0.60。激素诱导未对精液中脂肪酸组成产生显著影响。重要必需脂肪酸DHA、EPA、AA,以及n-3、n-6等重要种类的脂肪酸总量在激素诱导组与非诱导对照组样品间无显著差异;在激素诱导后的三个取样时间的样品间也无显著差异(P0.05)。     

一种新的海洋经济微藻——粉核油球藻

以Pinguiococcuspyrenoidosus CCMP 2004为实验藻种,研究分析了藻粉的基本生化组成和培养周期中PUFAs组成与含量的动态变化.结果表明,该藻的蛋白质量分数为37.54%,粗脂肪为27.45%,其中PUFAs包括18:2,18:3,18:4,20:4(AA,Arachidonic acid),20:5(EPA,Eicosapentaenoic acid),22:4(DTA,Docosatetraenoic acid)和22:6(DHA,Docosahexaenoic acid).该藻PUFAs的组成特征是EPA含量高,质量分数为20.93%,其他不饱和脂肪酸(16 : 3,16:4,18:3和18 : 4)的含量极微.分析结果显示粉核油球藻的营养价值较高,是一种新的具有商业化开发潜力的海洋微藻.     

不同培养条件对三角褐指藻生长及其生物活性成分积累的影响

以三角褐指藻(Phaeodactylum tricornutum)为研究材料,比较了Na NO3、NH4HCO3和CO(NH2)2为氮源的两种培养基(m L1和ASW培养基)对其生长和生物活性成分(岩藻黄素、金藻昆布糖和二十碳五烯酸(C20:5,EPA))时相积累的影响,同时分析了脂肪酸组成和总脂含量的变化。结果表明:以m L1培养基培养时,三角褐指藻的生物质质量浓度明显高于ASW培养基培养时的生物质质量质量浓度,尿素优于其他两种氮源,最大生物质质量质量浓度为3.7 g/L。不同培养条件下岩藻黄素含量的时相变化规律一致,均随着培养时间的延长呈现先增加后减少的趋势,其最高积累量分别为:13.27 mg/g(Na NO3)、13.23 mg/g(CO(NH2)2)和13.89 mg/g(NH4HCO3)(m L1);13.2 mg/g(Na NO3)、14.92 mg/g(CO(NH2)2)和13.6 mg/g(NH4HCO3)(ASW),由此可知氮源对岩藻黄素积累量影响不大。金藻昆布糖含量随着培养时间延长逐渐增加,其最大积累量分别为9.82 mg/g(NH4HCO3)(m L1)和8.59 mg/g(Na NO3)(ASW)。不同培养条件下其总脂含量变化不显著,均在培养末期达到最大值,分别为24.18%(NH4HCO3)(m L1)和23.79%(Na NO3)(ASW);其主要脂肪酸组成为:豆蔻酸(C14:0)、棕榈酸(C16:0)、棕榈油酸(C16:1)、硬脂酸(C18:0)、油酸(C18:1)、亚油酸(C18:2)、花生一烯酸(C20:1)、木焦油酸(C24:0)和EPA,其中,EPA含量随着培养时间延长逐渐下降,尿素最有利于EPA的积累。     

Depth-stratified phytoplankton dynamics in Cyclone Opal, a subtropical mesoscale eddy

As part of E-Flux III cruise studies in March 2005, we investigated phytoplankton community dynamics in a cyclonic cold-core eddy (Cyclone Opal) in the lee of the Hawaiian Islands. Experimental incubations were conducted under in situ temperature and light conditions on a drift array using a two-treatment dilution technique. Taxon-specific estimates of growth, grazing and production rates were obtained from analyses of incubation results based on phytoplankton pigments, flow cytometry and microscopy. Cyclone Opal was sampled at a biologically and physically mature state, with an 80–100 m doming of isopycnal surfaces in its central region and a deep biomass maximum of large diatoms. Depth-profile experimentation defined three main zones. The upper (mixed) zone (0–40 m), showed little compositional or biomass response to eddy nutrient enrichment, but growth, grazing and production rates were significantly enhanced in this layer relative to the ambient community outside of the eddy. Prochlorococcus spp. dominated the upper mixed layer, accounting for 50–60% of its estimated primary production both inside and outside of Opal. In contrast, the deep zone of 70–90 m showed little evidence of growth rate enhancement and was principally defined by a 100-fold increase of large (>20-μm) diatoms and a shift from Prochlorococcus to diatom dominance (80%) of production. The intermediate layer of 50–60 m marked the transition between the upper and lower extremes but also contained an elevated biomass of physiologically unhealthy diatoms with significantly depressed growth rates and proportionately greater grazing losses relative to diatoms above or below. Microzooplankton grazers consumed 58%, 65% and 55%, respectively, of the production of diatoms, Prochlorococcus and the total phytoplankton community in Cyclone Opal. The substantial grazing impact on diatoms suggests that efficient recycling was the major primary fate of diatom organic production, consistent with the low export fluxes and selective export of biogenic silica, as empty diatom frustules, in Cyclone Opal.     

Appearance of Chelophyes appendiculata and Abylopsis tetragona (Cnidaria, Siphonophora) in the Bay of Villefranche, northwestern Mediterranean

The vertical and temporal distribution of two calycophoran siphonophores, Chelophyes appendiculata (Eschscholtz, 1829) and Abylopsis tetragona (Otto, 1823) in the Bay of Villefranche (northwestern Mediterranean) was investigated by an analysis of three different planktonic time series. A daily series (1993–1995) showed seasonal peaks of the nectophores of C. appendiculata during spring and particularly in late summer, while the abundance of A. tetragona remained similar throughout the year. A weekly series (1994–1995) showed that C. appendiculata (nectophores and eudoxids) became concentrated above the thermal discontinuity, in the most stratified and warm waters, whereas A. tetragona was collected in large numbers below this discontinuity. A 27-year survey (1966–1993) showed long-term fluctuations of these siphonophore populations, which became abundant in the Bay starting from 1980 and especially after 1984, when the water column grew warm and hypersaline, corresponding to a less rainy period. Temporal (seasonal and long-term) and bathymetric (between 10 and 60 m depth) successions of these two siphonophores were noted in this shallow coastal bay.     

Biomarker responses to pollution in two invertebrate species: Scrobicularia plana and Nereis diversicolor from the Cádiz bay (SW Spain)

The clam Scrobicularia plana and the polychaete worm Nereis diversicolor were collected in several sites from a littoral enclosure in SW Spain. The aim of our study was to relate various biomarker responses in these species to a pollution gradient caused by untreated domestic discharges and to verify the adequacy of the selected species as sentinels in this habitat. The biomarkers selected were the antioxidant enzymes catalase (CAT), glutathione peroxidase (GPX) and DT-diaphorase (DT-D). In addition, the activities of cytochrome P450-dependent ethoxyresorufin O-deethylase (EROD) activity, the phase II detoxifying enzyme glutathione S-transferase (GST) and the neurotoxicity marker acetylcholinesterase (AChE) were measured. Metallothionein levels were selected as biomarkers of heavy metals exposure in both species. The results suggest a different response in the water filtering organism (clam) and the sediment eater (polychaete), probably as a consequent of different pollution exposure and that samples from the “Caño Sancti-Petri” were exposed to biologically active compounds that altered some of their biochemical responses. AChE was the most sensitive biomarker in both species and N. diversicolor proved to be a more robust sentinel in this ecosystem.     

红树林下人工笼养中华乌塘鳢(Bostrychus sinensis)肌肉营养成分的分析与评价

红树林因其独特的生长环境,具有重要的生态、经济和社会意义。中华乌塘鳢(Bostrychus sinensis)是我国优良的养殖品种。为提高红树林的生态与经济效益,对红树林下中华乌塘鳢铁笼养殖技术进行研究探讨,并分析比较红树林下养殖鱼、光滩笼养鱼与野生鱼肌肉的营养成分。结果显示:以上各组鱼体的粗蛋白含量均较高(74.65%~83.08%),粗脂肪含量较低(0.89%~1.63%),其中红树林下养殖鱼的粗蛋白和粗脂肪含量分别高于光滩养殖鱼;各组实验鱼的氨基酸总量(71.72%~79.27%)、鲜味氨基酸总量(29.03%~30.92%)、必需氨基酸总量(27.47%~31.57%)、非必需氨基酸总量(44.25%~47.69%)均以野生鱼为最高,光滩投饵组最低,红树林下养殖组高于光滩养殖组;各组实验鱼肌肉必需氨基酸指数EAAI均较高(66.83~74.90),限制性氨基酸为缬氨酸、异亮氨酸和(蛋+胱)氨酸,支链氨基酸总量/芳香族氨基酸总量(F值)为2.17~2.22;红树林下养殖鱼肌肉中的n-3系列多不饱和脂肪酸含量和(EPA+DHA)含量均分别高于光滩养殖鱼,红树林下养殖的中华乌塘鳢肌肉脂肪酸组成比光滩养殖鱼具有更高的营养价值。     

Esterification of vertebrate-like steroids in the eastern oyster (Crassostrea virginica)

The esterification of two model vertebrate steroid hormones – estradiol (E2) and dehidroepiandrosterone (DHEA) – was studied in the oyster Crassostrea virginica. The activity of acyl-CoA:steroid acyltransferase was characterized in microsomal fractions isolated from oyster digestive glands. The apparent K_m and V_max values changed with the fatty acid acyl-CoA used (C20:4, C18:2, C18:1, C16:1, C18:0 or C16:0), and were in the range of 9–17 μM, and 35–74 pmol/min/mg protein for E2, and in the range of 45–120 μM, and 30–182 pmol/min/mg protein for DHEA. Kinetic parameters were also assessed in gonadal tissue. The enzyme saturated at similar concentrations, although conjugation rates were lower than in digestive gland. Preliminary data shows that tributyltin (TBT) in the low μM range (1–50) strongly inhibits E2 and DHEA esterification, the esterification of E2 being more sensitive to inhibition than that of DHEA. Overall, results indicate that apolar conjugation occurs in oysters, in both digestive gland and gonads, at a very similar rate to mammals, suggesting that this is a well conserved conjugation pathway during evolution. Esterification, together with other mechanisms, can modulate endogenous steroid levels in C. virginica, and might be a target for endocrine disrupters, such as TBT.     

Oxidative stress in Laeonereis acuta (Polychaeta, Nereididae): environmental and seasonal effects

Laeonereis acuta was seasonally collected in an industrially polluted site (P) and in an unpolluted site (UP) at the Patos Lagoon estuary (southern Brazil). Glutathione S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) activity (U/mg protein) was determined in five groups of worms from each site. Metallothionein (MT – μmol GSH/g ww) and lipid peroxides content (LPO – nmoles of cumene hydroperoxide/g ww) were also measured. Annual mean values for CAT (UP=3.7±0.3; P=5.7±0.6), GST (UP=0.034±0.003; P=0.045±0.004) and MT (UP=0.15±0.02; P=0.23±0.03) were higher (p<0.05) in worms from the P site. In autumn, CAT activity was higher (p<0.05) in worms from the P site (7.6 ± 1.3) than in those from the UP site (3.6 ± 0.4). In summer, MT concentration was higher in worms from the P site (0.37 ± 0.03) than in those from the UP site (0.19 ± 0.01). No significant difference (p>0.05) in the LPO content was observed in worms from the different sites or collected in different seasons. These results indicate that worms from the polluted site showed higher antioxidant responses than those from the unpolluted site, sufficient to prevent oxidative damage in terms of LPO.     

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.     

投喂四种饵料对曼氏无针乌贼(Sepiella maindroni)繁殖性能的影响

以双齿围沙蚕、泥鳅、黄鲫、福寿螺4种不同饵料强化培育胴长(6.50±0.20)cm的曼氏无针乌贼,用曼氏无针乌贼肝脏和卵巢的氨基酸与脂肪酸变化、亲体产卵量、卵径、卵子孵化率及其幼体成活率等指标来评价4种饵料对其繁殖性能的影响.结果表明,黄鲫组曼氏无针乌贼肝脏与卵巢中∑EAA、∑SEAA、∑EAA+SEAA、∑NEAA、∑AA含量在第一次卵巢成熟与第二次卵巢成熟时均显著高于其它投喂组(P＜0.05).黄鲫组乌贼肝脏DHA/EPA在第一次卵巢成熟时显著高于其它投喂组,在第二次卵巢成熟时DHA、DHA/EPA、∑n3PUFA、∑n6PUFA、∑n3/n6PUFA都显著高于其它投喂组(P＜0.05);该组乌贼第一次卵巢成熟卵巢DHA、∑n3PUFA、∑n6PUFA、∑n3/n6PUFA及在第二次卵巢成熟时卵巢DHA、DHA/EPA、∑n3PUFA、∑n3/n6PUFA均显著高于其它投喂组(P＜0.05),该组第二次卵巢成熟时∑n6PUFA百分含量与沙蚕组无显著差异(P＞0.05).产卵量多少顺序为黄鲫组＞沙蚕组＞泥鳅组＞福寿螺组(P＜0.05);孵化率高低顺序为黄鲫组＞福寿螺组＞泥鳅组＞沙蚕组(P＜0.05);所产卵子平均直径大小顺序为黄鲫组＞泥鳅组＞沙蚕组＞福寿螺组(P＜0.05);幼体成活率高低顺序为黄鲫组＞泥鳅组＞沙蚕组、福寿螺组(P＜0.05).各指标吻合程度高.     

短角异剑水蚤对克氏双锯鱼稚鱼成活、生长和脂肪酸组成的影响

为评估短角异剑水蚤(Apocyclops royi)作为海水鱼类仔稚鱼的饵料价值和投喂效果,比较分析了其与卤虫无节幼体(Artemia nauplii)的脂肪酸组成及2种生物饵料对克氏双锯鱼(Amphiprion clarkii)稚鱼存活、生长和脂肪酸组成的影响。结果显示,短角异剑水蚤DHA、EPA和ARA含量分别达21.185%、11.088%和3.250%,海水仔稚鱼必需脂肪酸(EFA)总含量高达37.417%,均显著高于卤虫无节幼体。投喂短角异剑水蚤的克氏双锯鱼稚鱼(5~20 d)成活率(80.71%±8.23%)与投喂卤虫无节幼体组(76.30%±7.00%)差异不显著;稚鱼体长(7.75 mm±1.18 mm)、体重(0.0163 g±0.0080 g)和体长特定生长率(3.46%±0.75%)均显著高于卤虫无节幼体投喂组;稚鱼体内DHA(21.843%)、EPA(6.914%)和ARA(2.725%)含量也均显著高于后者。研究表明,短角异剑水蚤适于作为海水鱼类仔稚鱼的生物饵料,在水产养殖中具有广阔的应用前景。     

The feeding habits of Austrolethops wardi, a gobiid fish inhabiting burrows of the thalassinidean shrimp Neaxius acanthus

The feeding habit of Austrolethops wardi (Gobiidae) in the seagrass beds of Barrang Lompo and Bone Batang Island in the Spermonde Archipelago, South West Sulawesi, Indonesia, was investigated through gut content analysis. The feeding preferences of this species are very similar on both islands: A. wardi, a burrow associate of Neaxius acanthus, was found to feed almost exclusively on seagrass (which was found in 100% of the investigated stomachs and made up >94% of food items). However, seagrass epiphytes (<5% of food items) and animal food (<1% of food items) occurred in the guts as well, the latter predominantly in terms of copepods and to a lesser degree in other small invertebrates. These results indicate that animal food is of little importance for A. wardi. Some specimens even contained no parts of animal food.     

Potential source and diagenetic signatures of oceanic dissolved and particulate organic matter as distinguished by lipid biomarker distributions

Potential biogenic sources of ultrafiltered dissolved and suspended particulate organic matter (UDOM and POM, respectively) from the Sargasso Sea (SS) and North Central Pacific (NCP) Ocean were investigated using lipid biomarker compounds. Organic carbon (OC) concentrations were ~ 20–40 times greater in UDOM than POM and decreased with depth. However, total OC-normalized lipid concentrations were 2–3 orders of magnitude higher in POM than in UDOM. Particulate total lipids decreased 3–10-fold with depth, compared to 10–20% for dissolved total lipids. Total fatty acids (FA), the most abundant lipids, showed similar patterns as total lipids, comprising ~ 62–88% of the total lipids analyzed in UDOM and ~ 57–84% in POM.FA were dominated by straight-chain saturated compounds followed by monounsaturated, polyunsaturated, and branched FA. Polyunsaturated FA were enriched in POM vs. UDOM and in surface vs. deep waters for both UDOM and POM, likely reflecting the algal origins and greater reactivity of surface-derived materials. In both UDOM and POM, sterols of planktonic origin dominated, including cholest-5-en-3β-ol (C₂₇Δ⁵), 24-methylcholesta-5,24(28)E-dien-3β-ol (C₂₈Δ^5,24(28)) and 24-ethylcholest-5-3β-ol (C₂₉Δ⁵), with varying contributions from cholesta-5,22E-3β-ol (C₂₇Δ^5,22), 24-methylcholesta-5,22E-3β-ol (C₂₈Δ^5,22) and 24-ethylcholesta-5,22E-3β-ol (C₂₉Δ^5,22).Factor analysis of lipid biomarkers showed major differences between the UDOM and POM pools and for each pool as a function of depth, but not between the SS and NCP. While UDOM and POM biomarkers were both dominated by autochthonous sources, differences between the two pools suggest potential effects from some combination of source and diagenetic factors. The lipid biomarker data are further evaluated relative to previous studies of radiocarbon (¹⁴C) and elemental (C:N:P) characteristics of UDOM and POM in the SS and NCP.     

Reproductive cycle and minimal length at sexual maturity of Engraulis encrasicolus (L.) in the Zrmanja River estuary (Adriatic Sea, Croatia)

The reproductive cycle of anchovy, Engraulis encrasicolus (L.), was studied from monthly random samples of purse seine catches. A total of 1477 anchovy specimens were collected from January to December 2003 in the Zrmanja River estuary (Novigrad Sea). The analysis was based on the temporal evolution of gonadosomatic index, mass and stage of gonads. The total length of anchovy ranged from 4.5 to 14.5 cm and mass from 0.56 to 19.80 g. Sex ratio was slightly different from 1:1; the females were insignificantly predominated (♂/♀ = 0.99). The period of reproductive activity was from April to September coinciding with the most developed stages of gonads as well as with the highest gonad weights, and gonadosomatic indices. To estimate the length at maturity, a sub sample of 454 anchovy was taken from May to July (peak of anchovy spawning period). The length at which 50% of anchovy were mature (L₅₀) was calculated to be 8.2 cm. The length–weight relationship of anchovy was described by the expression: W = 3.51 × 10⁻³ L_T^3.211 (r² = 0.998). The relationships between total length–standard length and total length–fork length are L_T = 1.1405L_S + 0.2420 and L_T = 1.0425 L_F + 0.3944, respectively.     

Population structure, density and food sources of Terebralia palustris (Potamididae: Gastropoda) in a low intertidal Avicennia marina mangrove stand (Inhaca Island, Mozambique)

Population structure and distribution of Terebralia palustris were compared with the environmental parameters within microhabitats in a monospecific stand of Avicennia marina in southern Mozambique. Stable carbon and nitrogen isotope analyses of T. palustris and potential food sources (leaves, pneumatophore epiphytes, and surface sediments) were examined to establish the feeding preferences of T. palustris. Stable isotope signatures of individuals of different size classes and from different microhabitats were compared with local food sources. Samples of surface sediments 2.5–10 m apart showed some variation (−21.2‰ to −23.0‰) in δ¹³C, probably due to different contributions from seagrasses, microalgae and mangrove leaves, while δ¹⁵N values varied between 8.7‰ and 15.8‰, indicating that there is a very high variability within a small-scale microcosm. Stable isotope signatures differed significantly between the T. palustris size classes and between individuals of the same size class, collected in different microhabitats. Results also suggested that smaller individuals feed on sediment, selecting mainly benthic microalgae, while larger individuals feed on sediment, epiphytes and mangrove leaves. Correlations were found between environmental parameters and gastropod population structure and distribution vs. the feeding preferences of individuals of different size classes and in different microhabitats. While organic content and the abundance of leaves were parameters that correlated best with the total density of gastropods (>85%), the abundance of pneumatophores and leaves, as well as grain size, correlated better with the gastropod size distribution (>65%). Young individuals (height < 3 cm) occur predominantly in microhabitats characterized by a low density of leaf litter and pneumatophores, reduced organic matter and larger grain size, these being characteristic of lower intertidal open areas that favour benthic microalgal growth. With increasing shell height, T. palustris individuals start occupying microhabitats nearer the mangrove trees characterized by large densities of pneumatophores and litter, as well as sediments of smaller grain size, leading to higher organic matter availability in the sediment.