The reactions of the Norway lobster,Nephrops norvegicus (L.), to water currents

Observations were made on the reactions of the Norway lobster, Nephrops norvegicus, to water currents in a sea‐water flume tank. Blind animals were used to prevent visually‐guided behaviour. Nephrops adopted a downstream orientation, and usually walked downstream, in response to water current speeds in the range of 0.07 to 0.20 ms^?1. Patterns of water flow around the body revealed that it was most effectively streamlined when the animal adopted a downstream orientation. Direct measurements of the forces acting on the body revealed that animals with a downstream orientation experienced the least hydrodynamic drag and the greatest downforce.     

The effect of temperature on the bacterial load and microbial composition in Norway lobster (Nephrops norvegicus) tail meat during storage

Aims: The aim of this study was to update and extend our knowledge of the bacterial load and microbial composition in Norway lobster (Nephrops norvegicus) under commercially relevant storage conditions to optimize handling procedures. Methods and Results: Total viable counts were performed at different storage temperatures (0, 4, 8, 10, 12 or 16°C) and after different storage times (1–7 days). Storage at 16°C was found to be most detrimental, and storage at 0°C was found to be optimal. 16S‐rRNA sequencing was utilized to determine the composition of the bacteria within the microflora. In this way, Photobacterium isolates, especially Photobacterium phosphoreum, were identified as the main specific spoilage organisms. The abilities to reduce trimethylamineoxide (TMAO) and to produce H₂S were analysed in a selection of bacterial isolates. The higher the incubation temperature during storage, the more isolates were found to reduce TMAO and produce H₂S. Conclusions: Nephrops norvegicus possesses an unusually high initial microbial load when fresh. Storage temperature is the most crucial factor affecting microbial growth, microbial activity and spoilage potential in N. norvegicus produce. Spoilage can be attributed mainly to P. phosphoreum. Significance and Impact of the Study: This study presents significant new findings with regard to the progression and causative agents of spoilage in N. norvegicus. Based on the results, we can recommend that N. norvegicus tails should be stored in a 0°C environment immediately after catch. Stored this way, the growth and spoilage activity of the microflora may be reduced significantly and an extension of shelf life might be attained.     

The ovarian maturation cycle of the Norway lobster Nephrops norvegicus (Linnaeus, 1758) (Crustacea,Decapoda) from the western Mediterranean Sea

Summary

The Norway lobster Nephrops norvegicus lives in the continental margins of the western Mediterranean Sea at depths between 100 and 600 m. It constitutes an important fisheries resource and presents a seasonal reproductive pattern. Female Norway lobsters were obtained each month from a vessel fishing off Barcelona. One hundred females caught in June 2002 were kept in the laboratory. After spawning, ovarian samples were taken every 30 days with the objective of monitoring the first steps in ovarian maturation. The gonado-somatic index (GSI) remained low over the 6 months during which the females carried their eggs, plus for a further 2–3 months. However, this study suggests that ovarian maturation is a continuous process with two different phases, taking at least 6–8 months during which the female carries its eggs. There is an increase in oocyte numbers; the germinal zone produces oogonia; and the oocytes that develop migrate to the periphery, pushing the post-ovulatory follicles to the wall of the ovary and reinforcing it for subsequent spawning. Besides this increase in the number of oocytes, vitellogenesis begins 2–3 months after the eggs hatch. Oocytes then grow and the ovaries gain weight and change from a cream color to a blackish-green. When the GSI reached 10, spawning occurred and, from then on, the ovary is mainly composed of post-ovulatory follicles.     

Histochemical heterogeneity of fibers in the abdominal superficial flexor muscles of the Norway lobster, Nephrops norvegicus (L.).

The superficial flexor muscle in the abdomen of the Norway lobster Nephrops norvegicus (L.), comprises medial and lateral bundles with distinct fiber type composition. Fibers of the medial bundle have long sarcomeres (> 9 microns) and a thick fringe of subsarcolemmal mitochondria. In histochemical tests they have a low total myofibrillar ATPase activity, a pH-stable isoform of myosin ATPase, and a high level of oxidative enzyme activity. A few fibers of the lateral bundle also display these morphological and histochemical properties. However, the majority of lateral fibers have shorter sarcomeres (< 8 microns), no subsarcolemmal mitochondria, but a well-developed tubular system. They also have a higher total myofibrillar ATPase activity, a pH-labile isoform of myosin ATPase, and a low level of oxidative enzyme activity. The heterogeneous pattern of different fiber types in the lateral bundle of this muscle is similar but not identical in the different abdominal segments and in different individuals.     

Internal anatomy and ultrastructure of the male reproductive system of the Norway lobster Nephrops norvegicus (Decapoda: Astacidea)

The Norway lobster (Nephrops norvegicus) is economically important in Europe. However, apart from the female reproductive system, very little is known about its internal anatomy. This article focuses on studying the internal anatomy and ultrastructure of the male reproductive system. This system follows the general pattern found among decapod crustaceans, with several peculiarities. Testes are composed of lobular sperm ducts in which the spermatozoa are fully constituted. The spermatozoa present three lateral arms and a long acrosome, which gives a false appearance of flagellated spermatozoa. The two testes form a double H under the heart, and the vas deferens (VD) arise from each side at the posterior edge of the double H. The main characteristic of the VD is the presence of a sphincter in the enlarged area of the distal end of the middle VD. The MVD here shows an increase in musculature of the wall as compared to the VD, which regulates the passage of the sperm cord to the distal VD (DVD) and thence to the thelycum of the female. The wall of the spermatophore is formed in the distal part of the proximal VD, which surrounds the unique sperm cord present in the VD. Isolated spermatophores are not observed in the VD. The sperm cord is pinched off during copulation by the musculature of the DVD. Then, a portion of the sperm cord is transferred from each VD to form the isolated spermatophores. The wall of the spematophores and the spermatozoa that are observed inside the thelycum have the same morphology as those observed in the VD. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.     

Cu2+, Co2+, and Mn2+ modify the gating kinetics of high-voltage-activated Ca2+ channels in rat palaeocortical neurons

The effects of three divalent metal cations (Mn2+, Co2+, and Cu2+) on high-voltage-activated (HVA) Ca2+ currents were studied in acutely dissociated pyramidal neurons of rat piriform cortex using the patch-clamp technique. Cu2+, Mn2+, and Co2+ blocked HVA currents conducted by Ba2+ ( IBa) with IC50 of approximately 920 nM, approximately 58 micro M, and approximately 65 micro M, respectively. Additionally, after application of non-saturating concentrations of the three cations, residual currents activated with substantially slower kinetics than control IBa. As a consequence, the current fraction abolished by the blocking cations typically displayed, in its early phase, an unusually fast-decaying transient. The latter phenomenon turned out to be a subtraction artifact, since none of the pharmacological components (L-, N-, P/Q-, and R-type) that constitute the total HVA currents under study showed a similarly fast early decay: hence, the slow activation kinetics of residual currents was not due to the preferential inhibition of a fast-activating/inactivating component, but rather to a true slowing effect of the blocker cations. The percent IBa-amplitude inhibition caused by Mn2+, Co2+, and Cu2+ was voltage-independent over the whole potential range explored (up to +30 mV), hence the slowing of IBa activation kinetics was not due to a mechanism of voltage- and time-dependent relief from block. Moreover, Mn2+, Co2+, and Cu2+ significantly reduced I(Ba) deactivation speed upon repolarization, which also is not compatible with a depolarization-dependent unblocking mechanism. The above results show that 1) Cu2+ is a particularly potent HVA Ca2+-channel blocker in rat palaeocortical neurons; and 2) Mn2+, Co2+, and Cu2+, besides exerting a blocking action on HVA Ca2+-channels, also modify Ca2+-current activation and deactivation kinetics, most probably by directly interfering with channel-state transitions.     

Differences in the condition of Norway lobsters (Nephrops norvegicus (L.)) from trawled and creeled fishing areas

The condition of trawled and creeled Norway lobsters, Nephrops norvegicus, was compared in individuals caught along the Swedish west coast. Female and male N. norvegicus were collected from trawled and creeled areas in the spring and autumn. Their nutritional state was determined by analysing individuals for haemocyanin concentration, the dry weight/wet weight relationship in muscle and hepatopancreas and the percentage dry weight of muscle and hepatopancreas of total animal dry weight. All parameters were measured on an individual basis and checked for size dependence. Creeled individuals were generally found to be in better condition than individuals from trawled areas, and animal condition increased from spring to autumn. Autumn males from creeled sites were overall in the best condition, having the highest mean haemocyanin concentration, muscle and hepatopancreas dry weight/wet weight relationship and percentage dry weight of muscle tissue. Claw symmetry (paired cutters) was suggested as an indicator of limb loss, with the highest occurrence found in females from trawled sites. Crusher absence had no effect on the animal's individual percentage dry weight of muscle, although the mean was lower in trawled females than in other groups. Resource limitation and physical stress are discussed as possible underlying factors affecting the observed differences.     

Effect of insulin and contraction up on glucose transport in skeletal muscle

The major glucose transporter protein expressed in skeletal muscle is GLUT4. Both muscle contraction and insulin induce translocation of GLUT4 from the intracellular pool to the plasma membrane. The intracellular pathways that lead to contraction- and insulin-stimulated GLUT4 translocation seem to be different, allowing the attainment of a maximal effect when acting together. Insulin utilizes a phosphatidylinositol 3-kinase-dependent mechanism, whereas the exercise signal may be initiated by calcium release from the sarcoplasmic reticulum or from autocrine- or paracrine-mediated activation of glucose transport. During exercise skeletal muscle utilizes more glucose than when at rest. However, endurance training leads to decreased glucose utilization during sub-maximal exercise, in spite of a large increase in the total GLUT4 content associated with training. The mechanisms involved in this reduction have not been totally elucidated, but appear to cause the decrease of the amount of GLUT4 translocated to the plasma membrane by altering the exercise-induced enhancement of glucose transport capacity. On the other hand, the effect of resistance training is controversial. Recent studies, however, demonstrated the improvement in insulin sensitivity correlated with increasing muscle mass. New studies should be designed to define the molecular basis for these important adaptations to skeletal muscle. Since during exercise the muscle may utilize insulin-independent mechanisms to increase glucose uptake, the mechanisms involved should provide important knowledge to the understanding and managing peripheral insulin resistance.     

Bioaccumulation of cobalt in silkworm (Bombyx mori L.) in relation to mulberry, soil and wastewater metal concentrations

The present study was planned to evaluate Co(II) toxicity in silkworm population. The soil was irrigated using synthetic wastewater to determine the effects of pH and initial cobalt concentration in its bioaccumulation in silkworm (Bombyx mori L.) food chain. The amount of cobalt in wastewater, soil, mulberry and silkworm was determined by atomic absorption spectrophotometer (AAS) analysis. The obtained results clearly indicate that silkworm can be used as template to indicate local cobalt pollution as its body length, body weight and mortality rate was found to be strongly related to cobalt concentration. Higher the cobalt amount in mulberry leaves more the toxicity to silkworm population. At 400 mg/L Co concentration and pH 4 there was maximum deposition of Co in the soil from the synthetic effluent. However, in plants and silk worm the accumulation of Co was maximum at pH 4.5 at an initial Co concentration of 400 mg/L in the synthetic effluent. The maximum cobalt found in wastewater, soil, mulberry and silkworm was 400 ± 0.01, 273.5 ± 0.04, 42.85 ± 0.01, 36.62 ± 0.22 mg/kg, respectively.     

Accumulation of manganese in the haemolymph, nerve and muscle tissue of Nephrops norvegicus (L.) and its effect on neuromuscular performance

Exposure of Norway lobsters, Nephrops norvegicus (L.) for 3 weeks to manganese concentrations, (5 & 10 mg Mn l(-1) (90-180 microM)), led to its accumulation in various body tissues. The highest concentration was in nerve tissue (brain and abdominal ganglia) which had up to 6 times (on wet wt. basis) the manganese concentration of the exposure concentration, whereas the haemolymph accumulated 3 times and the muscle tissue only 0.5 times the exposure concentration. In the haemolymph the manganese was bound mainly to protein, predominantly (80-90%) to the respiratory protein haemocyanin, as the concentration was 14 times higher in the protein fraction than in the supernatant. Manganese did not substitute for copper in the haemocyanin, as the copper concentration remained constant despite the manganese exposure. The possibility that manganese exposure induced neurotoxic effects sufficient to reduce neuromuscular performance was assessed from the kinematics of free tail-flip swimming, and from measures of the forces produced by abdominal movements in tethered animals. No significant reduction in tail flip velocity or flexion force, but a significant reduction in the maximum post-flip extension force was found. No correlation was found between the manganese concentration in a single tissue or different fractions of the haemolymph and the post-flip extension, except for a weak negative correlation with the manganese concentration in the abdominal ganglion. The ecophysiological implications of these results are discussed.     

The effects of Mn2+ and Ca2+ on the prolonged depolarising after-potential in barnacle photoreceptor

We have studied the effects on the PDA of modifying intracellular and extracellular concentrations of Ca²⁺ and Mn²⁺. The effect of decreased Ca²⁺ concentration or addition of EGTA is mainly an increase in the PDA amplitude and length. Raising Ca²⁺ concentration using ruthenium red or high external Ca²⁺ has the opposite effect. The effect of Mn²⁺ is much more striking: In the presence of 50–100 mM Mn²⁺ the PDA is initially greatly depressed but can rise slowly for up to 20 or 30 s (in the dark) until it approaches its original amplitude and time course. Bridge measurements showed that the depression of the PDA corresponds to a depressed conductance and so is not due to an increase in K⁺ conductance. The Mn²⁺ effect is potentiated by decreased Ca²⁺. Appropriate stimulation suppresses the rising PDA as promptly as it does a normal PDA, suggesting that if lateral diffusion is the source of the slow rise, the PDA and PDA-depressing processes must be spatially linked. The action of the anti-PDA is apparently prolonged by both Ca²⁺ and Mn²⁺.Based on material presented at the European Neurosciences Meeting, Florence, September 1978     

The lobster fiefs: Economic and ecological effects of territoriality in the maine lobster industry

Lobstermen from each community along the coast of central Maine claim inshore fishing rights in particular areas. Although their claims are unrecognized by the state, they are well established and backed by surreptitious violence. Two kinds of lobstering territories exist, here termed nucleated and perimeterdefended, which differ essentially in the extent to which exclusive fishing rights are maintained. These differences in territorial organization affect the fishing effort of lobstermen, which in turn has a strong biological and economic impact.On leave 1974–1975 to serve with the National Marine Fisheries Service, Washington, D.C.The research on which this paper is based was financed by the National Marine Fisheries Service (Contract No. N-043-30-72) and a Faculty Research Grant from the University of Maine in 1973.     

New dinuclear Co(II) and Mn(II) complexes of the phenol-based compartmental ligand containing formyl and amine functions: structural, spectroscopic and magnetic properties

The phenol-based compartmental ligand Hpy2ald contains a tridentate amino arm and a weak donor aldehyde group at the 2^′ and at the 6^′ positions of the phenol ring, respectively. This ligand reacts with cobalt(II) perchlorate, cobalt(II) tetrafluoroborate and manganese(II) perchlorate, yielding dinuclear complexes, where two metal ions are doubly bridged by two deprotonated cresolate moieties. The coordination environment around the metal ions is then completed to a very distorted octahedron by three nitrogen donor atoms from the pendant amino arm and the oxygen atom of the aldehyde group. The crystal structures of the complexes, their spectroscopic and magnetic properties are reported.     

MS analysis of chondroitin polymerization: effects of Mn2+ ions on the stability of UDP-sugars and chondroitin synthesis

Chondroitin polymerase from Escherichia coli strain K4 (K4CP) synthesizes chondroitin (CH) polysaccharides by the alternate addition of N-acetyl-D-galactosamine (GalNAc) and D-glucuronic acid (GlcA) to acceptor CH oligosaccharides in the presence of Mn(2+) ions. In this study, we applied matrix-assisted laser desorption ionization and time-of-flight mass spectrometry (MALDI-TOF MS) for the further characterization of the products synthesized by K4CP from CH hexasaccharide as an initial acceptor and UDP-GalNAc and UDP-GlcA as donors. The analysis identified individual CH chains of various lengths and enabled the calculation of their average molecular weights. The ion peaks of the CH chains synthesized in the short-time reactions demonstrated not only the alternate addition of GlcA and GalNAc but also the more frequent transfer of GlcA and GalNAc, consistent with our previous kinetic data. In contrast, the MS spectra of the chains synthesized in the long-time reaction showed that CH chains containing GalNAc at the nonreducing ends were more abundant than those containing GlcA. We found that this inconsistency was due to the preferential decomposition of UDP-GlcA by Mn(2+) ions. We defined the optimal conditions to yield further elongation of the CH chains that have nearly equal numbers of GlcA and GalNAc residues at the nonreducing ends.     

Effects of contraction duration on low-frequency fatigue in voluntary and electrically induced exercise of quadriceps muscle in humans

The aims of this study were to investigate if low-frequency fatigue (LFF) dependent on the duration of repeated muscle contractions and to compare LFF in voluntary and electrically induced exercise. Male subjects performed three 9-min periods of repeated isometric knee extensions at 40% maximal voluntary contraction with contraction plus relaxation periods of 30 plus 60 s, 15 plus 30 s and 5 plus 10 s in protocols 1, 2 and 3, respectively. The same exercise protocols were repeated using feedback-controlled electrical stimulation at 40% maximal tetanic torque. Before and 15 min after each exercise period, knee extension torque at 1, 7, 10, 15, 20, 50 and 100 Hz was assessed. During voluntary exercise, electromyogram root mean square (EMG_rms) of the vastus lateralis muscle was evaluated. The 20-Hz torque:100-Hz torque (20:100 Hz torque) ratio was reduced more after electrically induced than after voluntary exercise (P < 0.05). During electrically induced exercise, the decrease in 20:100 Hz torque ratio was gradually (P < 0.05) reduced as the individual contractions shortened. During voluntary exercise, the decrease in 20:100 Hz torque ratio and the increase in EMG_rms were greater in protocol 1 (P < 0.01) than in protocols 2 and 3, which did not differ from each other. In conclusion, our results showed that LFF is dependent on the duration of individual muscle contractions during repetitive isometric exercise and that the electrically induced exercise produced a more pronounced LFF compared to voluntary exercise of submaximal intensity. It is suggested that compensatory recruitment of faster-contracting motor units is an additional factor affecting the severity of LFF during voluntary exercise. Accepted: 5 November 1997     

An attempt to predict long-term effects of atmospheric nitrogen deposition on the yield of Norway spruce stands (Picea abies (L.) Karst.) in southwestern Sweden

Long-term field experiments in Norway spruce stands on fertile sites (site indices 27–35 m) in southwestern Sweden were analysed with respect to volume increment. Three treatments were included (0=No fertilization, N = Fertilization with N, NP = Fertilization with N and P).Volume growth was monitored for 18 years in 10 blocks. No significant differences in annual volume increment between the treatments were detected. Volume increments in the N treatment were 97%, 99% and 107% as high as those in the 0 treatment for the periods 1–5, 6–10 and 11–15 years after the first fertilization. Corresponding values for the NP treatment were 104%, 108% and 110%, indicating that P has a small positive effect.The amount of N-fertilization would correspond to an annual N deposition of 20 kg ha^-1 during the next 30 years in southwestern Sweden. For this period, the results imply that this N deposition would not affect the growth of Norway spruce stands on fertile sites.     

Effect of deuterium oxide on contraction characteristics and ATPase activity in glycerinated single rabbit skeletal muscle fibers

We studied the effect of deuterium oxide (D₂O) on contraction characteristics and ATPase activity of single glycerinated muscle fibers of rabbit psoas. D₂O increased the maximum isometric force P₀ by about 20%, while the force versus stiffness relation did not change appreciably. The maximum shortening velocity under zero load V_max did not change appreciably in D₂O, so that the force-velocity (P-V) curve was scaled depending on the value of P₀. The Mg-ATPase activity of the fibers during generation of steady isometric force P₀ was reduced by about 50% in D₂O. Based on the Huxley contraction model, these results can be accounted for in terms of D₂O-induced changes in the rate constants f₁ and g₁ for making and breaking actin-myosin linkages in the isometric condition, in such a way that f₁/(f₁+g₁) increases by about 20%, while (f₁+g₁) remains unchanged. The D₂O effect at the molecular level is discussed in connection with biochemical studies on actomyosin ATPase.     

Distribution of Nephrops norvegicus (L.) larvae in the western Irish Sea: an example of advective control on recruitment

Results of a survey of Nephrops norvegicus larvae conductedin the western Irish Sea during May 1984 are discussed. Thelarval distributions show a pronounced tongue of high numbersextending southward from the muddy area where they are hatched.The inferred density-driven circulation at the time of the surveyis consistent with the southward transport of larvae. BecauseN.norvegicus requires a muddy substrate for successful larvalsettlement, the processes which influence the circulation mayprovide an important control on the level of recruitment.     

Soil changes in different age classes of Norway spruce (Picea abies (L.) Karst.) on afforested farmland

The aim of this study was to test the hypothesis that afforestation changes the content and distribution of soil organic carbon, nutrients and pH in the A-horizon of land previously used in agriculture, and that such soil changes depend on stand development. The investigation was evaluated as a completely randomised design with three treatments representing different age classes of trees: 20 years (Y20), 40 years (Y40) and 55 years (Y55). Eighteen trial plots, six per treatment, were established in plantations of Picea abies (L.) Karst. on soils of similar texture and mineralogy. Tree volume was 220 m³ ha^-1 in Y20, 400 in Y40 and 440 m³ ha^-1 in Y55.Concentrations of carbon (C) and nitrogen (N) were significantly higher in the uppermost part of the soil in the older stands Y40 and Y55 than in Y20. The total amount of organic C in the litter layer plus the top 15 cm of the soil differed between age classes, with Y40 and Y55 having the largest amounts. A reference layer (15–20 cm) was used in calculating the amount of soil C that had accumulated in the horizon since afforestation, being about 10 tonnes ha^-1 of C in Y20 and 19 tonnes ha^-1 in Y40 and Y55.Cation exchange capacity (CEC) and base saturation (BS) was higher in the older stands. Carbon contents and CEC were strongly correlated. In Y40 and Y55, pH was significantly lower than in Y20 in the lower part of the soil horizon. There was a general decrease with depth of C, N, CEC, K⁺ and Mg²⁺ in the soil horizon. BS, Ca²⁺, Na⁺ and pH showed a somewhat different pattern of distribution, with deceasing values in the upper part of the soil horizon and increasing values in the lower part of the soil horizon.Abbreviations BD Bulk density - CEC cation exchange capacity - BS base saturation - Ca²⁺ calcium ion - Mg²⁺ magnesium ion - K⁺ potassium ion - Na⁺ sodium ion - C carbon - Ca _a accumulated carbon content - C _t total carbon content - N nitrogen - Y20 age class 20 years - Y40 age class 40 years - Y55 age class 55 years