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| 3. |
- Elofsson, Rolf, et al.
(författare)
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Localization of monoaminergic neurons in the central nervous system of Astacus astacus Linne (Crustacea, Decapoda)
- 1966
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Ingår i: Zeitschrift für Zellforschung und mikroskopische Anatomie. ; 74, s. 464-473
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Tidskriftsartikel (refereegranskat)abstract
- The cellular localization of biogenic monoamines in crustaceans was studied by means of a highly specific and sensitive fluorescence method devised by Falck and Hillarp. It was found that neurons displaying specific fluorescence in the central nervous system were confined to the protocerebrum, the medulla externa and interna and the ventral nerve cord. The method allows a distinction between the fluorophores of 5-hydroxytryptamine (and 5-hydroxytryptophan), which emit the yellow light, and the fluorophores deriving from the catecholamines (and DOPA), which emit the green light. Green-fluorescent neurons occurred abundantly in the aforementioned parts of the central nervous system while yellow-fluorescent neurons were sparsely present in the same parts.
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| 4. |
- Spicer, J. I., et al.
(författare)
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Developmental changes in the responses of O-2 uptake and ventilation to acutely declining O-2 tensions in larval krill Meganyctiphanes norvegica
- 2003
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Ingår i: Journal of Experimental Marine Biology and Ecology. - 0022-0981. ; 295:2, s. 207-218
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Tidskriftsartikel (refereegranskat)abstract
- The effect of exposure to acutely declining oxygen tensions on O-2 uptake (Mo-2) and ventilation has been investigated in different larval stages of Northern krill Meganyctiphanes norvegica (calytopis III/ early furcilia I, late furcilia I, furcilia III and V). An ability to regulate Mo-2 during acutely declining P-O2 began to appear about furcilia III (critical O-2 tension or P-c = 15.4 +/- 0.73 kPa) and had improved by furcilia V (P-c= 12.6 +/- 0.39 kPa). Hypoxia-related hyperventilation was achieved by an increase in pleopod (but not thoracic limb) activity (P-c similar to 11 kPa), a sensitivity which also appeared at, or just before, furcilia V even though an earlier stage (furcilia III) had a full compliment of functional setose pleopods. While this regulatory ability appeared as the gills were beginning to form, furcilia V is still early in gill ontogeny compared with adults. Preexposure to very moderate hypoxia (60% and 70% O-2 (saturation) of furcilia III and V resulted in substantial mortality, but where it did not (furcilia V, 80% O-2 saturation), there was no effect of keeping krill at this P-O2 on either M-O2 or ventilation, suggesting that the development of respiratory regulation in M. norvegica is not open to environmental influence in the same way as for other crustaceans. We suggest that ontogeny of pleopod control provides furcilia V+ with both a stronger means of propulsion, allowing the ontogeny of DVM but also with an ability to regulate M-O2 during exposure to acutely declining P(O2)s. The onset of respiratory regulation (furcilia V) preceded the onset of DVM (furcilia VI+). As pleopod ontogeny is associated intimately with the ontogeny of DVM and respiratory regulation, in the Gullmarsfjord this co-occurrence is fortuitous as krill can be required during DVM to migrate into hypoxic water which they are not equipped to deal with, in physiological terms, before furcilia V. (C) 2003 Elsevier B.V. All rights reserved.
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| 5. |
- Spicer, J. I., et al.
(författare)
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Diel vertical migration and the haemocyanin of krill Meganyctiphanes norvegica
- 2002
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 238, s. 153-162
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Tidskriftsartikel (refereegranskat)abstract
- Changes in environmental factors (PO2, temperature, salinity and food availability) influence the concentration of the respiratory pigment haemocyanin ([Hc]) present in many crustaceans. We investigated the possibility that [Hc] and HcO(2) affinity altered during the diel vertical migration (DVM) of Nordic krill Meganyctiphanes norvegica in the Gullmarsfjord, Sweden. The [Hc] decreased with increasing depth, for individuals both trawled and caged at different depths. Laboratory experiments indicated that this pattern could not be explained by differences in PO2, temperature or salinity. Alternatively, starvation had a significant effect on [Hc] over the course of a few h (less than or equal to10), i.e. a much shorter time scale than found for other crustacean species. Starved individuals showed a dramatic decrease in [Hc] compared with fed individuals. This decrease was exacerbated by an increase in temperature. We suggest that when M norvegica migrates into deep water during the day, for whatever reason (predator avoidance or reduced prey abundance, or reduced ability to locate and capture prey), they cannot secure enough energy to meet routine metabolic demands; they therefore break down Hc and use it as an energy source. We conclude that there is likely to be a trade-off between the respiratory function of Hc and its importance in nutrition when krill migrate into deeper, nutritionally poorer waters during their DVM.
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| 6. |
- Spicer, J. I., et al.
(författare)
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Metabolic responses to low salinity of the shipworm Teredo navalis (L.)
- 2003
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Ingår i: Sarsia. - 0036-4827. ; 88:4, s. 302-305
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Tidskriftsartikel (refereegranskat)abstract
- It has long been thought that shipworms are sensitive to salinity changes, but few studies have investigated this possibility. The oxygen uptake of excised gill tissue from individuals of a population of the shipworm Teredo navalis from southwest Sweden decreased with decreasing salinity. The greatest fall occurred between S = 4 and 8 PSU. Excised gill tissue showed little effect of salinity on ciliary beat rate at S greater than or equal to 3-4 PSU, but below this beating ceased. Individuals withdrew their siphons and sealed their bur-rows at S = 4-8 PSU. Burrows could remain closed at S < 4 PSU for at least 6 days at 22 degreesC. Siphons re-emerged within minutes of a return to S > 4 PSU. We conclude that a salinity range of 4-8 PSU is critical for this population of T. navalis. This fits well with information on salinity tolerance from other populations of this species.
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| 7. |
- Strömberg, Jarl-Ove, et al.
(författare)
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Northern krill, Meganyctiphanes norvegica, come up to see the last eclipse of the millennium?
- 2002
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Ingår i: Journal of the Marine Biological Association of the United Kingdom. - 0025-3154. ; 82:5, s. 919-920
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Tidskriftsartikel (refereegranskat)abstract
- Most krill species undergo diel vertical migration (DVM) which is to some extent influenced by light intensity. During a solar eclipse (11 August 1999) the upward and downward movement of krill, Meganyctiphanes norvegica, inhabiting a Swedish fjord followed closely changes in light intensity. Here the eclipse was partial (77%) and the weather overcast and yet krill at 70-90 m depth were able to detect, and respond to very small changes in light. This observation of an event during mid-day which is not pre-programmed confirms light as an important triggering mechanism for krill DVM.
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| 8. |
- Thomasson, M. A., et al.
(författare)
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Swimming capacity and pleopod beat rate as a function of sex, size and moult stage in Northern krill Meganyctiphanes norvegica
- 2003
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 250, s. 205-213
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Tidskriftsartikel (refereegranskat)abstract
- An experimental method to estimate the relative swimming capacity of pelagic crustaceans is proposed. Swimming capacity measured as propulsive force can be estimated by attaching the animal to a virtually friction free rotational displacement transducer with an arm allowing only forward and backward movements. The method also allows determination of beat rates of the pleopod cycle. Results from the use of the method on different sizes, sexes and moult stages of Northern krill Aleganyctiphanes norvegica indicate that the swimming capacity of krill increases with the size of the animal, although pleopod beat frequency decreases with increasing size of the animal. We found no difference in swimming capacity between females and males, but female krill had a higher pleopod beat frequency than males. The moult stage of the animal affects the swimming capacity, with newly moulted krill being weaker swimmers. It also affects pleopod beat frequency, with newly moulted krill having the lowest frequency. We argue that results of this kind may be useful in attempts to interpret observed demographic distribution patterns in migration studies as well as in studies of krill population dynamics.
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