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- Baden, Susanne P., 1952, et al.
(författare)
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Accumulation and elimination kinetics of manganese from different tissues of the Norway lobster Nephrops norvegicus (L.)
- 1999
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Ingår i: Aquatic Toxicology. - 0166-445X. ; 46:2, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- The exposure of marine benthic animals to dissolved manganese (Mn) occurs from metalliferous outlets or the enhanced flux of dissolved manganese from sediments during hypoxia. A prerequisite to valid interpretation of manganese concentrations measured in animals in situ is a thorough understanding of accumulation and elimination rates of this metal by relevant target tissues in organisms exposed to environmentally realistic manganese concentrations. Norway lobster, Nephrops norvegicus, accumulated manganese when exposed to solutions of < 0.06 (background), 5 and 10 mg Mn l(-1) for 20 days and was allowed to eliminate any accumulated manganese in undosed sea water for a further 20 days. During this period individual N. norvegicus were dissected into a number of components (brain, ventral ganglion, haemolymph, midgut gland, gills and exoskeleton) and the manganese concentration of each was analysed. Manganese accumulation reached a plateau after 1.25 days in all tissues except for midgut gland, which continued to accumulate manganese during the entire exposure period. In general, the manganese elimination was significantly slower than accumulation and reached a plateau after 1.25-2.5 days (except the gills) following exposure to clean sea water. The accumulation factor (AF), when compared to maximum concentrations in control and exposed animals, was highest in the haemolymph (x 88) followed by nerve tissue (x 22) at the 10 mg Mn l(-1) exposure. The concentration factor (CF), when comparing manganese accumulation in tissues (wet weight) with exposure concentration, was 1.2-3.5 and for most tissues was similar for both exposure concentrations or slightly higher in the 5 mg Mn l(-1) exposure-indicating net accumulation of manganese in all tissues with a saturation effect with increasing exposure concentrations. Thus, from these experiments it may be concluded that measured manganese concentrations in N. norvegicus give an indication of recent exposure to manganese concentrations in the bottom waters of their habitats. (C) 1999 Elsevier Science B.V. All rights reserved.
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| 3. |
- Eriksson, Susanne P., 1964, et al.
(författare)
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Behaviour and tolerance to hypoxia in juvenile Norway lobster (Nephrops norvegicus) of different ages
- 1997
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Ingår i: Marine Biology. - 0025-3162. ; 128:1, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- The annual occurrence of hypoxia (<25% oxygen saturation) in the bottom waters along the Swedish west coast coincides with the postlarval settlement of Norway lobster, Nephrops norvegicus (L.). This study investigates behaviour and the experimental effects of low oxygen concentrations in juvenile N. norvegicus of different ages. All experimental individuals were reared to the juvenile (postlarval) stage in the laboratory and then given sediment as a substratum. Behavioural responses to low oxygen concentrations were tested in early and late Postlarvae 1 exposed to normoxia (>80% oxygen saturation, pO(2) > 16.7 kPa), moderate hypoxia (30% oxygen saturation, pO(2) = 6.3 kPa) and hypoxia (25% oxygen saturation, pO(2) = 5.2 kPa). The experiments were run for a maximum period of 24 h or until individuals died. Behaviour was studied using sequential video recordings of four behavioural activities: digging, walking, inactivity or flight (escape swimming up into the water column). Behaviour and mortality changed with lowered oxygen concentrations; energetically costly activities (such as walking) were reduced, and activity in general declined. In normoxia, juveniles initially walked and then burrowed, but when exposed to hypoxia they were mainly inactive with occasional outbursts of escape swimming. To increase oxygen availability the juveniles were observed to raise their bodies on stilted legs (similar to adults in hypoxic conditions), but oxygen saturations of 25% were lethal within 24 h. The results suggest that the main gas exchanges of early postlarval stages occur over the general body surface. Burrowing behaviour was tested in Postlarvae 1 and 2 of different ages held in >80% oxygen saturation for 1 wk. The difference in time taken to complete a V-shaped depression or a U-shaped burrow was measured. The results showed a strong negative relationship between postlarval age and burrowing time, but all individuals made a burrow. Juveniles were more sensitive to hypoxia than adults. Thus, the possible consequences of episodic hypoxia for the recruitment of Nephrops norvegicus and for the recolonization of severely affected areas are discussed.
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| 4. |
- Eriksson, Susanne P., 1964, et al.
(författare)
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Manganese in the haemolymph and tissues of the Norway lobster, Nephrops norvegicus (L.), along the Swedish west coast, 1993-1995
- 1998
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Ingår i: Hydrobiologia. - 0018-8158. ; 376, s. 255-264
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Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal differences in manganese levels in Norway lobsters, Nephrops norvegicus, were compared with the concentrations of manganese in their environment. Animals were collected twice yearly (spring and autumn) from seven stations along the Swedish west coast and from one site in the Faroe Islands, during 1993-94, and analysed for manganese tissue concentration and content. Animals were also collected from the Swedish stations in the autumn of 1995 and compared with animals from a stressful environment, frequently exposed to hypoxia. There were large spatial differences and the animals collected in the Faroe Islands contained (in most tissues) one order of magnitude less manganese than the animals collected along the Swedish west coast. The manganese level of the haemolymph correlated most closely with the manganese concentration the animal was exposed to in the field. The manganese concentration of the female gonad tissue did however not differ with space nor time and remained stable around 5.1 mu g Mn g(-1) dw tissue throughout the investigation. Animals taken from an area with known repeated hypoxia in the bottom water, had high levels of manganese in especially the gills. Their mean manganese concentration was over 20 times higher (1560 mu g Mn g(-1) dw tissue) than the manganese concentration in animals from the other Swedish stations. They also had more than threefold the amount of manganese in the brain, giving a mean concentration of 193 mu g Mn g(-1) dw tissue.
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| 7. |
- Ejdung, Gunilla, 1953-
(författare)
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Predatory processes in Baltic benthos
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Baltic soft-bottom community is uniquely simple, with only a few benthic macro-faunal species, and is therefore well suited for mechanistic studies of inter-specific interactions. Two of the dominating organisms in this benthic community are the amphipod Monoporeia affinis and the bivalve Macoma balthica. Field surveys have shown that M. balthica is generally absent or scarce when the density of M. affinis is high. The hypothesis that adult M. affinis kill the newly settled bivalves was confirmed experimentally in the laboratory, and it was also shown that adult Pontoporeia femorata amphipods have a negative impact on bivalve survival. Further experiments, showed that juvenile M. affinis, contrary to earlier beliefs, can kill and presumably eat the newly settled M. balthica. The response of M. affinis to increased bivalve densities was a type III like functional response, indicating that bivalves at low densities find a partial refuge from amphipod predation.The effect of the predatory isopod Saduria entomon on the Macoma balthica population was assessed both in the laboratory and the field. In the laboratory, the presence of the isopod did not affect the small just settled bivalves (0.3 mm), whereas slightly larger and larger bivalves (>0.8 mm) suffered from increased mortality, as did bivalves in the three month long field study. The isopods are physically capable of opening quite large bivalves, a 34 mm long isopod can break open a 17 mm long bivalve, but given a choice, smaller bivalves are selected. When S. entomon is offered the two prey species, Monoporeia affinis and M. balthica, the amphipod is preferred, leaving the bivalve relatively safe from predation.In the aquatic environment, chemical substances released by predators or their activities can convey information, to which prey can respond, for example, by a change in behaviour. In a three-trophic-level food chain, species-specific chemical substances from a predatory fish, the short-horned sculpin (Myoxocephalus scorpius), directly affected the behaviour of the isopod Saduria entomon. The isopod remained buried in the sediment longer, and fewer prey amphipods, Monoporeia affinis, were eaten. Further, exposure to chemical substances from isopods feeding on amphipods, lead the amphipod to lower their swimming activity, whereas water from non-feeding isopods did not have this effect.
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| 8. |
- Holmes, Janet M, et al.
(författare)
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The effects of the metal ions Mn2+ and Co2+ on muscle contraction in the Norway lobster, Nephrops norvegicus (L.)
- 1999
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Ingår i: Journal of Comparative Physiology. B, Biochemical, Systemic, and Environmental Physiology. - : Springer Science and Business Media LLC. - 0174-1578 .- 1432-136X. ; 169, s. 402-410
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the metal ions manganese and cobalt on force production by the abdominal superficial flexor muscle of the Norway lobster, Nephrops norvegicus, have been studied in response to both neuronal stimulation and electrical field stimulation applied to an isolated neuromuscular preparation, and by selectively blocking synaptic transmission with Ivermectin. In response to both forms of stimulation, low concentrations of manganese added to the standard N. norvegicus saline increased the contractile force produced by the muscle, whereas higher concentrations of manganese inhibited both responses in a dose-dependent manner, until force was completely abolished at concentrations above 2.9 mM manganese. Cobalt ions produced similar effects, and no significant difference was found between the concentration of the two ions at 50% force inhibition (K-m) or between the two stimulation methods (manganese: 1.22 mM; cobalt: 1.29 mM, P = 0.86). This suggests that they have a similar mode of action, and a postsynaptic site of inhibition. These K-m values are considerably higher than the concentrations of these ions known to accumulate in the haemolymph of N. norvegicus under eutrophic conditions, and it therefore seems unlikely that accumulations of manganese or cobalt ions under such conditions would cause any significant inhibition of muscle contraction force.
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